NSTAR Electric Company PFD 4.25% (NSARP) 10-K27 Feb 202019 FY Annual reportFinancial data

Company Profile

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION - USD ($)	12 Months Ended
DOCUMENT AND ENTITY INFORMATION - USD ($)	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity Registrant Name	EVERSOURCE ENERGY
Entity Incorporation, State or Country Code	MA
Entity Address, Address Line One	300 Cadwell Drive
Entity Address, City or Town	Springfield
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01104
City Area Code	800
Local Phone Number	286-5000
Entity File Number	1-5324
Entity Tax Identification Number	04-2147929
Title of 12(b) Security	Common Shares, $5.00 par value per share
Trading Symbol	ES
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 24,486,439,602
Entity Common Stock, Shares Outstanding		329,952,663
Entity Central Index Key	0000072741
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
The Connecticut Light and Power Company
Entity Information [Line Items]
Entity Registrant Name	THE CONNECTICUT LIGHT AND POWER COMPANY
Entity Incorporation, State or Country Code	CT
Entity Address, Address Line One	107 Selden Street
Entity Address, City or Town	Berlin
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06037-1616
City Area Code	800
Local Phone Number	286-5000
Entity File Number	0-00404
Entity Tax Identification Number	06-0303850
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		6,035,205
Entity Central Index Key	0000023426
Current Fiscal Year End Date	--12-31
NSTAR Electric Company
Entity Information [Line Items]
Entity Registrant Name	NSTAR ELECTRIC COMPANY
Entity Incorporation, State or Country Code	MA
Entity Address, Address Line One	800 Boylston Street
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02199
City Area Code	800
Local Phone Number	286-5000
Entity File Number	1-02301
Entity Tax Identification Number	04-1278810
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		200
Entity Central Index Key	0000013372
Current Fiscal Year End Date	--12-31
Public Service Company of New Hampshire
Entity Information [Line Items]
Entity Registrant Name	PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE
Entity Incorporation, State or Country Code	NH
Entity Address, Address Line One	Energy Park
Entity Address, Address Line Two	780 North Commercial Street
Entity Address, City or Town	Manchester
Entity Address, State or Province	NH
Entity Address, Postal Zip Code	03101-1134
City Area Code	800
Local Phone Number	286-5000
Entity File Number	1-6392
Entity Tax Identification Number	02-0181050
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		301
Entity Central Index Key	0000315256
Current Fiscal Year End Date	--12-31

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets:
Cash	$ 15,432	$ 108,068
Receivables, Net	989,383	994,055
Unbilled Revenues	181,006	176,285
Fuel, Materials, Supplies and REC Inventory	235,471	238,042
Regulatory Assets	651,112	514,779
Prepayments and Other Current Assets	342,135	260,995
Total Current Assets	2,414,539	2,292,224
Property, Plant and Equipment, Net	27,585,470	25,610,428
Deferred Debits and Other Assets:
Regulatory Assets	4,863,639	4,631,137
Goodwill	4,427,266	4,427,266
Investments in Unconsolidated Affiliates	871,633	464,286
Marketable Securities	449,130	417,508
Other Long-Term Assets	512,238	398,407
Total Deferred Debits and Other Assets	11,123,906	10,338,604
Total Assets	41,123,915	38,241,256
Current Liabilities:
Notes Payable	889,084	910,000
Long-Term Debt – Current Portion	327,411	837,319
Rate Reduction Bonds – Current Portion	43,210	52,332
Accounts Payable	1,147,872	1,119,995
Regulatory Liabilities	361,152	370,230
Other Current Liabilities	836,834	823,006
Total Current Liabilities	3,605,563	4,112,882
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	3,755,777	3,506,030
Regulatory Liabilities	3,658,042	3,609,475
Derivative Liabilities	338,710	379,562
Asset Retirement Obligations	488,511	466,236
Accrued Pension, SERP and PBOP	1,370,245	962,510
Other Long-Term Liabilities	810,553	730,100
Total Deferred Credits and Other Liabilities	10,421,838	9,653,913
Capitalization:
Long-Term Debt	13,770,828	12,248,743
Rate Reduction Bonds	540,122	583,331
Noncontrolling Interest - Preferred Stock of Subsidiaries	155,570	155,570
Common Shareholders' Equity:
Common Shares	1,729,292	1,669,392
Capital Surplus, Paid In	7,087,768	6,241,222
Retained Earnings	4,177,048	3,953,974
Accumulated Other Comprehensive Income (Loss)	(65,059)	(60,000)
Treasury Stock	(299,055)	(317,771)
Common Shareholders' Equity	12,629,994	11,486,817
Commitments and Contingencies (Note 13)
Total Liabilities and Capitalization	41,123,915	38,241,256
The Connecticut Light and Power Company
Current Assets:
Cash	0	87,721
Receivables, Net	400,927	397,026
Accounts Receivable from Affiliated Companies	24,577	23,082
Unbilled Revenues	56,465	56,971
Fuel, Materials, Supplies and REC Inventory	50,700	44,529
Regulatory Assets	178,607	125,155
Prepayments and Other Current Assets	73,184	60,279
Total Current Assets	784,460	794,763
Property, Plant and Equipment, Net	9,625,765	8,909,701
Deferred Debits and Other Assets:
Regulatory Assets	1,557,261	1,505,488
Other Long-Term Assets	217,705	199,767
Total Deferred Debits and Other Assets	1,774,966	1,705,255
Total Assets	12,185,191	11,409,719
Current Liabilities:
Notes Payable to Eversource Parent	63,800	0
Long-Term Debt – Current Portion	0	250,000
Accounts Payable	374,698	324,983
Accounts Payable to Affiliated Companies	97,793	26,452
Obligations to Third Party Suppliers	56,952	56,248
Regulatory Liabilities	82,763	109,614
Derivative Liabilities	67,804	55,058
Other Current Liabilities	132,339	161,088
Total Current Liabilities	876,149	983,443
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,244,551	1,166,784
Regulatory Liabilities	1,164,991	1,122,157
Derivative Liabilities	338,594	379,536
Accrued Pension, SERP and PBOP	391,159	282,771
Other Long-Term Liabilities	147,586	155,495
Total Deferred Credits and Other Liabilities	3,286,881	3,106,743
Capitalization:
Long-Term Debt	3,518,136	3,004,016
Noncontrolling Interest - Preferred Stock of Subsidiaries	116,200	116,200
Common Shareholders' Equity:
Common Shares	60,352	60,352
Capital Surplus, Paid In	2,535,765	2,410,765
Retained Earnings	1,791,392	1,727,899
Accumulated Other Comprehensive Income (Loss)	316	301
Common Shareholders' Equity	4,387,825	4,199,317
Commitments and Contingencies (Note 13)
Total Liabilities and Capitalization	12,185,191	11,409,719
NSTAR Electric Company
Current Assets:
Cash	52	1,606
Receivables, Net	346,785	361,296
Accounts Receivable from Affiliated Companies	29,914	31,344
Unbilled Revenues	37,482	34,518
Fuel, Materials, Supplies and REC Inventory	124,060	114,202
Regulatory Assets	285,591	241,747
Prepayments and Other Current Assets	31,150	51,960
Total Current Assets	855,034	836,673
Property, Plant and Equipment, Net	9,472,770	8,794,700
Deferred Debits and Other Assets:
Regulatory Assets	1,250,029	1,196,512
Prepaid PBOP	166,058	132,810
Other Long-Term Assets	144,368	109,764
Total Deferred Debits and Other Assets	1,560,455	1,439,086
Total Assets	11,888,259	11,070,459
Current Liabilities:
Notes Payable	10,500	278,500
Notes Payable to Eversource Parent	30,300	0
Long-Term Debt – Current Portion	95,000	0
Accounts Payable	363,691	384,398
Accounts Payable to Affiliated Companies	96,307	89,636
Obligations to Third Party Suppliers	108,827	109,547
Renewable Portfolio Standards Compliance Obligations	150,429	139,898
Regulatory Liabilities	209,180	190,620
Other Current Liabilities	71,333	74,872
Total Current Liabilities	1,135,567	1,267,471
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,357,265	1,294,467
Regulatory Liabilities	1,516,585	1,513,279
Accrued Pension, SERP and PBOP	108,243	14,145
Other Long-Term Liabilities	320,629	263,096
Total Deferred Credits and Other Liabilities	3,302,722	3,084,987
Capitalization:
Long-Term Debt	3,247,086	2,944,846
Noncontrolling Interest - Preferred Stock of Subsidiaries	43,000	43,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	1,813,442	1,633,442
Retained Earnings	2,346,287	2,098,091
Accumulated Other Comprehensive Income (Loss)	155	(1,378)
Common Shareholders' Equity	4,159,884	3,730,155
Commitments and Contingencies (Note 13)
Total Liabilities and Capitalization	11,888,259	11,070,459
Public Service Company of New Hampshire
Current Assets:
Cash	413	1,439
Receivables, Net	99,934	104,854
Accounts Receivable from Affiliated Companies	6,763	8,444
Unbilled Revenues	48,146	47,145
Taxes Receivable	1,497	25,913
Fuel, Materials, Supplies and REC Inventory	24,957	37,504
Regulatory Assets	84,053	67,228
Special Deposits	32,513	47,498
Prepayments and Other Current Assets	17,934	17,564
Total Current Assets	316,210	357,589
Property, Plant and Equipment, Net	3,129,506	2,880,073
Deferred Debits and Other Assets:
Regulatory Assets	861,672	862,288
Other Long-Term Assets	43,270	27,406
Total Deferred Debits and Other Assets	904,942	889,694
Total Assets	4,350,658	4,127,356
Current Liabilities:
Notes Payable to Eversource Parent	27,000	57,000
Long-Term Debt – Current Portion	0	150,000
Rate Reduction Bonds – Current Portion	43,210	52,332
Accounts Payable	127,081	111,292
Accounts Payable to Affiliated Companies	37,946	26,029
Regulatory Liabilities	65,766	55,526
Accrued Interest	19,138	19,953
Other Current Liabilities	32,736	44,093
Total Current Liabilities	352,877	516,225
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	506,212	481,221
Regulatory Liabilities	413,381	428,069
Accrued Pension, SERP and PBOP	157,638	124,457
Other Long-Term Liabilities	37,075	36,339
Total Deferred Credits and Other Liabilities	1,114,306	1,070,086
Capitalization:
Long-Term Debt	951,620	655,173
Rate Reduction Bonds	540,122	583,331
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	903,134	678,134
Retained Earnings	490,306	627,258
Accumulated Other Comprehensive Income (Loss)	(1,707)	(2,851)
Common Shareholders' Equity	1,391,733	1,302,541
Commitments and Contingencies (Note 13)
Total Liabilities and Capitalization	$ 4,350,658	$ 4,127,356

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Revenues	$ 8,526,470	$ 8,448,201	$ 7,751,952
Operating Expenses:
Purchased Power, Fuel and Transmission	3,040,160	3,138,969	2,535,271
Operations and Maintenance	1,363,113	1,335,213	1,307,052
Depreciation	885,278	819,930	773,802
Amortization of Regulatory Assets/(Liabilities), Net	195,380	252,026	89,986
Energy Efficiency Programs	501,369	472,380	480,835
Taxes Other Than Income Taxes	711,035	729,753	676,757
Impairment of Northern Pass Transmission	239,644	0	0
Total Operating Expenses	6,935,979	6,748,271	5,863,703
Operating Income	1,590,491	1,699,930	1,888,249
Interest Expense	533,197	498,805	421,755
Other Income, Net	132,777	128,366	107,913
Income Before Income Tax Expense	1,190,071	1,329,491	1,574,407
Income Tax Expense	273,499	288,972	578,892
Net Income	916,572	1,040,519	995,515
Net Income Attributable to Noncontrolling Interests	7,519	7,519	7,519
Net Income Attributable to Common Shareholders	$ 909,053	$ 1,033,000	$ 987,996
Basic Earnings Per Common Share (in dollars per share)	$ 2.83	$ 3.25	$ 3.11
Diluted Earnings Per Common Share (in dollars per share)	$ 2.81	$ 3.25	$ 3.11
Weighted Average Common Shares Outstanding:
Basic (in shares)	321,416,086	317,370,369	317,411,097
Diluted (in shares)	322,941,636	317,993,934	318,031,580
The Connecticut Light and Power Company
Operating Revenues	$ 3,232,551	$ 3,096,174	$ 2,887,359
Operating Expenses:
Purchased Power, Fuel and Transmission	1,188,202	1,095,187	930,780
Operations and Maintenance	549,167	506,448	502,107
Depreciation	301,188	278,557	249,352
Amortization of Regulatory Assets/(Liabilities), Net	51,621	129,021	83,166
Energy Efficiency Programs	118,235	93,977	114,713
Taxes Other Than Income Taxes	342,489	357,147	323,887
Total Operating Expenses	2,550,902	2,460,337	2,204,005
Operating Income	681,649	635,837	683,354
Interest Expense	151,357	151,727	142,973
Other Income, Net	17,531	22,663	22,991
Income Before Income Tax Expense	547,823	506,773	563,372
Income Tax Expense	136,971	129,056	186,646
Net Income	410,852	377,717	376,726
NSTAR Electric Company
Operating Revenues	3,044,642	3,112,926	2,980,629
Operating Expenses:
Purchased Power, Fuel and Transmission	1,064,289	1,257,073	1,025,414
Operations and Maintenance	468,436	462,100	482,924
Depreciation	296,500	276,372	274,008
Amortization of Regulatory Assets/(Liabilities), Net	103,735	46,654	33,831
Energy Efficiency Programs	289,206	292,288	294,053
Taxes Other Than Income Taxes	195,586	194,316	181,959
Total Operating Expenses	2,417,752	2,528,803	2,292,189
Operating Income	626,890	584,123	688,440
Interest Expense	114,198	105,193	105,729
Other Income, Net	44,577	53,066	34,100
Income Before Income Tax Expense	557,269	531,996	616,811
Income Tax Expense	125,313	148,906	242,085
Net Income	431,956	383,090	374,726
Public Service Company of New Hampshire
Operating Revenues	1,065,936	1,047,619	981,624
Operating Expenses:
Purchased Power, Fuel and Transmission	398,449	370,246	237,478
Operations and Maintenance	210,995	210,541	263,110
Depreciation	93,737	92,055	128,192
Amortization of Regulatory Assets/(Liabilities), Net	57,732	80,978	(16,577)
Energy Efficiency Programs	25,982	20,105	13,788
Taxes Other Than Income Taxes	62,574	77,280	89,760
Total Operating Expenses	849,469	851,205	715,751
Operating Income	216,467	196,414	265,873
Interest Expense	60,666	60,634	51,007
Other Income, Net	19,222	27,672	9,805
Income Before Income Tax Expense	175,023	163,452	224,671
Income Tax Expense	40,975	47,576	88,675
Net Income	$ 134,048	$ 115,876	$ 135,996

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Income	$ 916,572	$ 1,040,519	$ 995,515
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	1,393	1,756	1,974
Changes in Unrealized Gains/(Losses) on Marketable Securities	1,166	(547)	(350)
Change in Funded Status of Pension, SERP and PBOP Benefit Plans	(7,618)	5,194	(2,745)
Other Comprehensive (Loss)/Income, Net of Tax	(5,059)	6,403	(1,121)
Comprehensive Income Attributable to Noncontrolling Interests	(7,519)	(7,519)	(7,519)
Comprehensive Income Attributable to Common Shareholders	903,994	1,039,403	986,875
The Connecticut Light and Power Company
Net Income	410,852	377,717	376,726
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	(26)	51	334
Changes in Unrealized Gains/(Losses) on Marketable Securities	41	(19)	(12)
Other Comprehensive (Loss)/Income, Net of Tax	15	32	322
Comprehensive Income Attributable to Common Shareholders	410,867	377,749	377,048
NSTAR Electric Company
Net Income	431,956	383,090	374,726
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	437	437	438
Changes in Unrealized Gains/(Losses) on Marketable Securities	12	(5)	(3)
Change in Funded Status of Pension, SERP and PBOP Benefit Plans	1,084	13	(264)
Other Comprehensive (Loss)/Income, Net of Tax	1,533	445	171
Comprehensive Income Attributable to Common Shareholders	433,489	383,535	374,897
Public Service Company of New Hampshire
Net Income	134,048	115,876	135,996
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	1,075	1,104	1,162
Changes in Unrealized Gains/(Losses) on Marketable Securities	69	(33)	(21)
Other Comprehensive (Loss)/Income, Net of Tax	1,144	1,071	1,141
Comprehensive Income Attributable to Common Shareholders	$ 135,192	$ 116,947	$ 137,137

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Shares	Capital Surplus, Paid In	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	The Connecticut Light and Power Company	The Connecticut Light and Power CompanyCommon Shares	The Connecticut Light and Power CompanyCapital Surplus, Paid In	The Connecticut Light and Power CompanyRetained Earnings	The Connecticut Light and Power CompanyAccumulated Other Comprehensive Loss	NSTAR Electric Company	NSTAR Electric CompanyCommon Shares	NSTAR Electric CompanyCapital Surplus, Paid In	NSTAR Electric CompanyRetained Earnings	NSTAR Electric CompanyAccumulated Other Comprehensive Loss	Public Service Company of New Hampshire	Public Service Company of New HampshireCommon Shares	Public Service Company of New HampshireCapital Surplus, Paid In	Public Service Company of New HampshireRetained Earnings	Public Service Company of New HampshireAccumulated Other Comprehensive Loss
Beginning Balance (in shares) at Dec. 31, 2016		316,885,808						6,035,205					200					301
Beginning balance at Dec. 31, 2016	$ 10,711,734	$ 1,669,392	$ 6,250,224	$ 3,175,171	$ (65,282)	$ (317,771)	$ 3,470,387	$ 60,352	$ 2,110,714	$ 1,299,374	$ (53)	$ 3,342,843	$ 0	$ 1,500,642	$ 1,844,195	$ (1,994)	$ 1,387,357	$ 0	$ 843,134	$ 549,286	$ (5,063)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	995,515			995,515			376,726			376,726		374,726			374,726		135,996			135,996
Dividends on Common Stock	(602,083)			(602,083)			(254,800)			(254,800)		(272,000)			(272,000)		(173,900)			(173,900)
Dividends on Preferred Stock	(7,519)			(7,519)			(5,559)			(5,559)		(1,960)			(1,960)
Capital Stock Expenses, Net							51		51
Capital Contributions from Eversource Parent												2,300		2,300
Long-Term Incentive Plan Activity	(10,834)		(10,834)
Other Changes in Shareholders' Equity	550		550
Other Comprehensive Income (Loss)	(1,121)				(1,121)		322				322	171				171	1,141				1,141
Ending Balance (in shares) at Dec. 31, 2017		316,885,808						6,035,205					200					301
Ending balance at Dec. 31, 2017	11,086,242	$ 1,669,392	6,239,940	3,561,084	(66,403)	(317,771)	3,587,127	$ 60,352	2,110,765	1,415,741	269	3,446,080	$ 0	1,502,942	1,944,961	(1,823)	1,350,594	$ 0	843,134	511,382	(3,922)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,040,519			1,040,519			377,717			377,717		383,090			383,090		115,876			115,876
Dividends on Common Stock	(640,110)			(640,110)			(60,000)			(60,000)		(228,000)			(228,000)
Dividends on Preferred Stock	(7,519)			(7,519)			(5,559)			(5,559)		(1,960)			(1,960)
Return of Capital																	(530,000)		(530,000)
Capital Contributions from Eversource Parent	365,000						300,000		300,000			130,500		130,500					365,000
Long-Term Incentive Plan Activity	(543)		(543)
Other Changes in Shareholders' Equity	1,825		1,825
Other Comprehensive Income (Loss)	$ 6,403				6,403		32				32	445				445	1,071				1,071
Ending Balance (in shares) at Dec. 31, 2018	316,885,808	316,885,808						6,035,205					200					301
Ending balance at Dec. 31, 2018	$ 11,486,817	$ 1,669,392	6,241,222	3,953,974	(60,000)	(317,771)	4,199,317	$ 60,352	2,410,765	1,727,899	301	3,730,155	$ 0	1,633,442	2,098,091	(1,378)	1,302,541	$ 0	678,134	627,258	(2,851)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	916,572			916,572			410,852			410,852		431,956			431,956		134,048			134,048
Dividends on Common Stock	(685,979)			(685,979)			(341,800)			(341,800)		(181,800)			(181,800)		(271,000)			(271,000)
Dividends on Preferred Stock	$ (7,519)			(7,519)			(5,559)			(5,559)		(1,960)			(1,960)
Capital Contributions from Eversource Parent							125,000		125,000			180,000		180,000			225,000		225,000
Issuance of Common Shares (in shares)	11,980,000	11,980,000
Issuance of Common Shares	$ 868,550	$ 59,900	808,650
Long-Term Incentive Plan Activity	3,434		3,434
Issuance of Treasury Shares (in shares)		1,014,837
Issuance of Treasury Shares	69,474		50,758			18,716
Capital Stock Expense	(16,296)		(16,296)
Other Comprehensive Income (Loss)	$ (5,059)				(5,059)		15				15	1,533				1,533	1,144				1,144
Ending Balance (in shares) at Dec. 31, 2019	329,880,645	329,880,645						6,035,205					200					301
Ending balance at Dec. 31, 2019	$ 12,629,994	$ 1,729,292	$ 7,087,768	$ 4,177,048	$ (65,059)	$ (299,055)	$ 4,387,825	$ 60,352	$ 2,535,765	$ 1,791,392	$ 316	$ 4,159,884	$ 0	$ 1,813,442	$ 2,346,287	$ 155	$ 1,391,733	$ 0	$ 903,134	$ 490,306	$ (1,707)

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividends on common shares (in dollars per share)	$ 2.14	$ 2.02	$ 1.90
Per share par value (in dollars per share)	$ 5	$ 5

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Net Income	$ 916,572	$ 1,040,519	$ 995,515
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	885,278	819,930	773,802
Deferred Income Taxes	209,812	174,812	491,630
Uncollectible Expense	63,446	61,337	44,453
Pension, SERP and PBOP Expense, Net	22,000	5,498	22,454
Pension and PBOP Contributions	(121,782)	(194,947)	(242,800)
Regulatory (Under)/Over Recoveries, Net	(124,870)	34,920	(47,935)
Amortization	195,380	252,026	89,986
Payments Related to CYAPC's DOE Pre-1983 Spent Nuclear Fuel Obligation	(29,000)	(145,000)	0
Proceeds from DOE Spent Nuclear Fuel Litigation	68,840	0	0
Impairment of Northern Pass Transmission	239,644	0	0
Other	(196,087)	(111,225)	(204,421)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(98,716)	(141,433)	(117,155)
Fuel, Materials, Supplies and REC Inventory	(8,074)	(831)	(9,223)
Taxes Receivable/Accrued, Net	(16,129)	(67,770)	52,284
Accounts Payable	14,866	24,481	56,067
Other Current Assets and Liabilities, Net	(11,603)	78,226	91,545
Net Cash Flows Provided by Operating Activities	2,009,577	1,830,543	1,996,202
Investing Activities:
Investments in Property, Plant and Equipment	(2,911,489)	(2,569,936)	(2,348,105)
Proceeds from Sales of Marketable Securities	566,592	900,749	832,903
Proceeds from Sales of Marketable Securities Used to Pay Pre-1983 Spent Nuclear Fuel Obligation	0	145,000	0
Purchases of Marketable Securities	(537,258)	(908,387)	(810,507)
Acquisition of Aquarion	0	0	(877,652)
Investments in Unconsolidated Affiliates, Net	(416,337)	(205,150)	(32,634)
Proceeds from the Sale of PSNH Generation Assets	0	193,924	0
Other Investing Activities	24,204	6,754	5,479
Net Cash Flows Used in Investing Activities	(3,274,288)	(2,437,046)	(3,230,516)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	852,254	0	0
Cash Dividends on Common Shares	(663,239)	(640,110)	(602,083)
Cash Dividends on Preferred Stock	(7,519)	(7,519)	(7,519)
Increase/(Decrease) in Notes Payable	325,370	(379,310)	72,810
(Repayments)/Issuance of Rate Reduction Bonds	(52,332)	635,663	0
Issuance of Long-Term Debt	1,520,000	2,200,000	2,500,000
Retirement of Long-Term Debt	(801,078)	(1,050,330)	(745,000)
Other Financing Activities	(1,006)	(28,457)	(4,754)
Net Cash Flows Provided by/(Used in) Financing Activities	1,172,450	729,937	1,213,454
Net (Decrease)/Increase in Cash and Restricted Cash	(92,261)	123,434	(20,860)
Cash and Restricted Cash - Beginning of Year	209,324	85,890	106,750
Cash and Restricted Cash - End of Year	117,063	209,324	85,890
The Connecticut Light and Power Company
Operating Activities:
Net Income	410,852	377,717	376,726
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	301,188	278,557	249,352
Deferred Income Taxes	54,005	54,859	119,295
Uncollectible Expense	15,948	15,831	5,312
Pension, SERP and PBOP Expense, Net	12,761	8,943	9,909
Pension and PBOP Contributions	(24,000)	(41,150)	(2,500)
Regulatory (Under)/Over Recoveries, Net	(24,653)	(53,372)	(8,017)
Amortization of Regulatory Assets, Net	51,621	129,021	83,166
Other	(80,266)	(69,786)	(42,973)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(52,746)	(67,334)	(47,768)
Fuel, Materials, Supplies and REC Inventory	(6,171)	3,909	3,612
Taxes Receivable/Accrued, Net	(23,089)	8,954	(9,688)
Accounts Payable	102,344	(76,924)	48,032
Other Current Assets and Liabilities, Net	(11,350)	18,846	21,860
Net Cash Flows Provided by Operating Activities	726,444	588,071	806,318
Investing Activities:
Investments in Property, Plant and Equipment	(917,532)	(864,136)	(824,383)
Other Investing Activities	714	209	236
Net Cash Flows Used in Investing Activities	(916,818)	(863,927)	(824,147)
Financing Activities:
Cash Dividends on Common Shares	(341,800)	(60,000)	(254,800)
Cash Dividends on Preferred Stock	(5,559)	(5,559)	(5,559)
(Decrease)/Increase in Notes Payable to Eversource Parent	63,800	(69,500)	(10,600)
Issuance of Long-Term Debt	500,000	500,000	525,000
Retirement of Long-Term Debt	(250,000)	(300,000)	(250,000)
Capital Contributions from Eversource Parent	125,000	300,000	0
Other Financing Activities	12,291	(7,091)	15,004
Net Cash Flows Provided by/(Used in) Financing Activities	103,732	357,850	19,045
Net (Decrease)/Increase in Cash and Restricted Cash	(86,642)	81,994	1,216
Cash and Restricted Cash - Beginning of Year	91,613	9,619	8,403
Cash and Restricted Cash - End of Year	4,971	91,613	9,619
NSTAR Electric Company
Operating Activities:
Net Income	431,956	383,090	374,726
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	296,500	276,372	274,008
Deferred Income Taxes	27,107	41,438	110,499
Uncollectible Expense	25,079	22,279	21,252
Pension, SERP and PBOP Expense, Net	(12,399)	(21,521)	(9,509)
Pension and PBOP Contributions	(6,359)	(61,751)	(90,721)
Regulatory (Under)/Over Recoveries, Net	(60,863)	149,647	(20,009)
Amortization of Regulatory Assets, Net	103,735	46,654	33,831
Other	(78,220)	(65,523)	(24,872)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(11,087)	(26,403)	(50,896)
Fuel, Materials, Supplies and REC Inventory	(9,858)	(18,685)	(24,610)
Taxes Receivable/Accrued, Net	14,147	(33,900)	39,205
Accounts Payable	(22,659)	37,140	(20,421)
Other Current Assets and Liabilities, Net	1,194	51,674	26,849
Net Cash Flows Provided by Operating Activities	698,273	780,511	639,332
Investing Activities:
Investments in Property, Plant and Equipment	(861,391)	(725,766)	(719,623)
Other Investing Activities	86	58	(3,552)
Net Cash Flows Used in Investing Activities	(861,305)	(725,708)	(723,175)
Financing Activities:
Cash Dividends on Common Shares	(181,800)	(228,000)	(272,000)
Cash Dividends on Preferred Stock	(1,960)	(1,960)	(1,960)
Increase/(Decrease) in Notes Payable	(268,000)	44,500	56,500
Increase in Notes Payable to Eversource Parent	30,300	0	0
Issuance of Long-Term Debt	400,000	0	700,000
Retirement of Long-Term Debt	0	0	(400,000)
Capital Contributions from Eversource Parent	180,000	130,500	2,300
Other Financing Activities	(3,855)	108	(1,796)
Net Cash Flows Provided by/(Used in) Financing Activities	154,685	(54,852)	83,044
Net (Decrease)/Increase in Cash and Restricted Cash	(8,347)	(49)	(799)
Cash and Restricted Cash - Beginning of Year	14,659	14,708	15,507
Cash and Restricted Cash - End of Year	6,312	14,659	14,708
Public Service Company of New Hampshire
Operating Activities:
Net Income	134,048	115,876	135,996
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	93,737	92,055	128,192
Deferred Income Taxes	15,917	35,924	63,883
Uncollectible Expense	6,726	6,383	6,704
Pension, SERP and PBOP Expense, Net	417	754	1,368
Pension and PBOP Contributions	(15,400)	0	(800)
Regulatory (Under)/Over Recoveries, Net	(26,288)	(27,264)	(30,788)
Amortization of Regulatory Assets, Net	57,732	80,978	(16,577)
Other	(28,228)	(15,363)	(16,813)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(210)	(19,307)	(22,055)
Fuel, Materials, Supplies and REC Inventory	1,902	16,928	5,519
Taxes Receivable/Accrued, Net	25,374	(19,970)	339
Accounts Payable	12,281	(10,147)	29,453
Other Current Assets and Liabilities, Net	(3,573)	3,028	16,463
Net Cash Flows Provided by Operating Activities	274,435	259,875	300,884
Investing Activities:
Investments in Property, Plant and Equipment	(308,993)	(323,910)	(312,720)
Proceeds from the Sale of PSNH Generation Assets	0	193,924	0
Proceeds from the Sale of Property	0	4,782	0
Other Investing Activities	1,023	437	199
Net Cash Flows Used in Investing Activities	(307,970)	(124,767)	(312,521)
Financing Activities:
Cash Dividends on Common Shares	(271,000)	(150,000)	(23,900)
(Decrease)/Increase in Notes Payable to Eversource Parent	(30,000)	(205,900)	102,000
(Repayments)/Issuance of Rate Reduction Bonds	(52,332)	635,663	0
Return of Capital	0	(530,000)	0
Issuance of Long-Term Debt	300,000	0	0
Retirement of Long-Term Debt	(150,000)	(199,250)	(70,000)
Capital Contributions from Eversource Parent	225,000	365,000	0
Other Financing Activities	(4,168)	(89)	(225)
Net Cash Flows Provided by/(Used in) Financing Activities	17,500	(84,576)	7,875
Net (Decrease)/Increase in Cash and Restricted Cash	(16,035)	50,532	(3,762)
Cash and Restricted Cash - Beginning of Year	52,723	2,191	5,953
Cash and Restricted Cash - End of Year	$ 36,688	$ 52,723	$ 2,191

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Dec. 31, 2019
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES A. About Eversource, CL&P, NSTAR Electric and PSNH Eversource Energy is a public utility holding company primarily engaged, through its wholly-owned regulated utility subsidiaries, in the energy delivery business. Eversource Energy's wholly-owned regulated utility subsidiaries consist of CL&P, NSTAR Electric and PSNH (electric utilities), Yankee Gas and NSTAR Gas (natural gas utilities) and Aquarion (water utilities). Eversource provides energy delivery and/or water service to approximately four million electric, natural gas and water customers through eight regulated utilities in Connecticut, Massachusetts and New Hampshire. Eversource, CL&P, NSTAR Electric and PSNH are reporting companies under the Securities Exchange Act of 1934. Eversource Energy is a public utility holding company under the Public Utility Holding Company Act of 2005. Arrangements among the regulated electric companies and other Eversource companies, outside agencies and other utilities covering interconnections, interchange of electric power and sales of utility property are subject to regulation by the FERC. Eversource's regulated companies are subject to regulation of rates, accounting and other matters by the FERC and/or applicable state regulatory commissions (the PURA for CL&P, Yankee Gas and Aquarion, the DPU for NSTAR Electric, NSTAR Gas and Aquarion, and the NHPUC for PSNH and Aquarion). CL&P, NSTAR Electric and PSNH furnish franchised retail electric service in Connecticut, Massachusetts and New Hampshire. Yankee Gas and NSTAR Gas are engaged in the distribution and sale of natural gas to customers within Connecticut and Massachusetts, respectively. Aquarion is engaged in the collection, treatment and distribution of water in Connecticut, Massachusetts and New Hampshire. CL&P, NSTAR Electric and PSNH's results include the operations of their respective distribution and transmission businesses. The distribution business also includes the results of NSTAR Electric's solar power facilities and PSNH's generation facilities prior to sale in 2018. PSNH completed the sales of all its thermal and hydroelectric generation assets in 2018. See Note 14, "Generation Asset Sale," for further information. Eversource Service, Eversource's service company, and several wholly-owned real estate subsidiaries of Eversource, provide support services to Eversource, including its regulated companies. B. Basis of Presentation The consolidated financial statements of Eversource, NSTAR Electric and PSNH include the accounts of each of their respective subsidiaries. Intercompany transactions have been eliminated in consolidation. The accompanying consolidated financial statements of Eversource, NSTAR Electric and PSNH and the financial statements of CL&P are herein collectively referred to as the "financial statements." The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Eversource consolidates the operations of CYAPC and YAEC, both of which are inactive regional nuclear generation companies engaged in the long-term storage of their spent nuclear fuel. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's and PSNH's combined ownership and voting interests in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and the CYAPC and YAEC companies have been eliminated in consolidation of the Eversource financial statements. Eversource's consolidated financial information includes the results of Aquarion and its subsidiaries beginning from the date of the acquisition on December 4, 2017. Eversource holds several equity ownership interests that are not consolidated and are accounted for under the equity method. In accordance with accounting guidance on noncontrolling interests in consolidated financial statements, the Preferred Stock of CL&P and the Preferred Stock of NSTAR Electric, which are not owned by Eversource or its consolidated subsidiaries and are not subject to mandatory redemption, have been presented as noncontrolling interests in the financial statements of Eversource. The Preferred Stock of CL&P and the Preferred Stock of NSTAR Electric are considered to be temporary equity and have been classified between liabilities and permanent shareholders' equity on the balance sheets of Eversource, CL&P and NSTAR Electric due to a provision in the preferred stock agreements of both CL&P and NSTAR Electric that grant preferred stockholders the right to elect a majority of the CL&P and NSTAR Electric Boards of Directors, respectively, should certain conditions exist, such as if preferred dividends are in arrears for a specified amount of time. The Net Income reported in the statements of income and cash flows represents net income prior to apportionment to noncontrolling interests, which is represented by dividends on preferred stock of CL&P and NSTAR Electric. Eversource's utility subsidiaries' electric, natural gas and water distribution and transmission businesses are subject to rate-regulation that is based on cost recovery and meets the criteria for application of accounting guidance for entities with rate-regulated operations, which considers the effect of regulation on the differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. See Note 2, "Regulatory Accounting," for further information. Certain reclassifications of prior year data were made in the accompanying financial statements to conform to the current year presentation. The Eversource and PSNH 2018 statements of cash flows, the 2018 supplemental cash flow information footnote, and the 2018 segment footnote were revised to correct an error in the presentation of non-cash capital additions. The impact of this revision on the statement of cash flows is an increase to operating cash inflows in Accounts Payable of $46.6 million and a corresponding increase to investing cash outflows in Investments in Property, Plant and Equipment for the year ended December 31, 2018. This revision is not deemed material, individually or in the aggregate, to the previously issued financial statements. As of both December 31, 2019 and 2018 , Eversource's carrying amount of goodwill was $4.43 billion . Eversource performs an assessment for possible impairment of its goodwill at least annually. Eversource completed its annual goodwill impairment test for each of its reporting units as of October 1, 2019 and determined that no impairment exists. See Note 25B, "Acquisition of Aquarion and Goodwill - Goodwill," for further information. C. Accounting Standards Accounting Standards Issued but Not Yet Effective: In June 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326), which provides a new model for recognizing credit losses on financial instruments based on an estimate of current expected credit losses. Under the new guidance, immediate recognition of credit losses expected over the life of a financial instrument is required. The standard is effective January 1, 2020. The Company assessed the impacts of this standard on the accounting for credit losses on its financial instruments, including accounts receivable, and does not expect a material impact on the financial statements of Eversource, CL&P, NSTAR Electric or PSNH. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes , which eliminates certain exceptions to the general principles of current income tax guidance in ASC 740, Income Taxes, and simplifies and improves consistency in application of that income tax guidance through clarifications of, and amendments to, ASC 740. The guidance is effective in the first quarter of 2021. The Company is evaluating the impact of this standard on the financial statements of Eversource, CL&P, NSTAR Electric and PSNH. Accounting Standards Recently Adopted: On January 1, 2019, the Company adopted ASU 2016-02, Leases (Topic 842), which amended existing lease accounting guidance. The Company applied the Topic 842 lease criteria to new leases and lease renewals entered into effective on or after January 1, 2019. The ASU required balance sheet recognition of leases deemed to be operating leases as well as additional disclosure requirements. The recognition, measurement and presentation of expenses and cash flows were not significantly changed. The Company utilized the modified retrospective transition method allowed in ASU 2018-11, Leases (Topic 842) - Targeted Improvements , which allowed the Company to adopt the new leases standard as of January 1, 2019, with prior periods presented in the financial statements continuing to follow existing lease accounting guidance under Topic 840 (Leases) in the accounting literature. Implementation of ASU 2018-11 had no effect on retained earnings, and the requirements of the new lease standard (Topic 842) are reflected in the 2019 financial statements and footnotes. The Company elected the practical expedient package whereby it did not need to reassess whether or not an existing contract is or contains a lease or whether a lease is an operating or capital lease, and it did not need to reassess initial direct costs for leases. Election of this practical expedient allowed us to carry forward our historical lease classifications. The Company elected the practical expedient to not reevaluate land easements existing at adoption if they were not previously accounted for as leases. The Company also elected to use the discount rate as of the January 1, 2019 implementation date to discount its operating lease liabilities. The Company did not elect the hindsight practical expedient to determine the lease term for existing leases. The Company determined the impact the ASUs had on its financial statements by reviewing its lease population and identifying lease data needed for the disclosure requirements. The Company implemented a new lease accounting system in 2019 to ensure ongoing compliance with the ASU’s requirements. Adoption of the new standard resulted in the recording of operating lease liabilities and right-of-use assets on the balance sheet upon transition at January 1, 2019 of $58.0 million at Eversource, $25.3 million at NSTAR Electric, $0.6 million at CL&P, and $0.6 million at PSNH. Implementation of the new guidance did not have an impact on each company’s results of operations or cash flows. D. Impairment of Northern Pass Transmission Northern Pass was Eversource's planned 1,090 MW HVDC transmission line that would have interconnected from the Québec-New Hampshire border to Franklin, New Hampshire and an associated alternating current radial transmission line between Franklin and Deerfield, New Hampshire. As a result of a final decision received on July 19, 2019 from the New Hampshire Supreme Court, whereby the court denied Northern Pass’ appeal and affirmed the NHSEC’s denial of Northern Pass’ siting application on NPT, Eversource concluded that construction of NPT was no longer probable and that there was no constructive path forward for the project. Eversource terminated the project and permanently abandoned any further development. As a result, substantially all of the capitalized project costs, which totaled $318 million , certain of which are subject to cost reimbursement agreements, were impaired. Based on the conclusion that the construction of Northern Pass was no longer probable, Eversource recorded an impairment charge in 2019 for all of the project costs associated with Northern Pass, which were primarily engineering design, siting, permitting and legal costs, along with appropriate allowances for funds used during construction, and recognized a receivable for certain cost reimbursement agreements. Additionally, Eversource recorded an impairment charge associated with the land acquired to construct Northern Pass in order to recognize the land at its estimated fair value based on assessed values and transaction costs. In total, this resulted in a pre-tax impairment charge of $239.6 million within Operating Income on the statement of income for the year ended December 31, 2019, and was reflected in the Electric Transmission segment. The after-tax impact of the impairment charge was $204.4 million , or $0.64 per share, after giving effect to the estimated fair value of the related land, reimbursement agreements, and the impact of expected income tax benefits associated with the impairment charge. As a result of the decision to terminate the NPT project and permanently abandon any further development, Eversource does not expect any future cash expenditures associated with this project. E. Cash Cash includes cash on hand. At the end of each reporting period, any overdraft amounts are reclassified from Cash to Accounts Payable on the balance sheets. F. Provision for Uncollectible Accounts Eversource, including CL&P, NSTAR Electric and PSNH, presents its receivables at estimated net realizable value by maintaining a provision for uncollectible accounts. This provision is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. The estimate is based upon historical collection and write-off experience and management's assessment of collectability from customers. Management continuously assesses the collectability of receivables and adjusts collectability estimates based on actual experience. Receivable balances are written off against the provision for uncollectible accounts when the customer accounts are terminated and these balances are deemed to be uncollectible. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows NSTAR Electric and NSTAR Gas to recover in rates, amounts associated with certain uncollectible hardship accounts receivable. These uncollectible hardship customer account balances are included in Regulatory Assets or Other Long-Term Assets on the balance sheets. The total provision for uncollectible accounts is included in Receivables, Net on the balance sheets. The provision for uncollectible hardship accounts is included in the total uncollectible provision balance. The provision balances were as follows: Total Provision for Uncollectible Accounts Provision for Uncollectible Hardship Accounts As of December 31, As of December 31, (Millions of Dollars) 2019 2018 2019 2018 Eversource $ 224.8 $ 212.7 $ 143.3 $ 131.5 CL&P 97.3 88.0 80.1 71.9 NSTAR Electric 75.4 74.5 43.9 42.5 PSNH 10.5 11.1 — — Uncollectible expense associated with customers' accounts receivable included in Operations and Maintenance expense on the statements of income was as follows: For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Eversource $ 63.4 $ 61.3 $ 44.5 CL&P 15.9 15.8 5.3 NSTAR Electric 25.1 22.3 21.3 PSNH 6.7 6.4 6.7 G. Transfer of Energy Efficiency Loans In 2018, CL&P transferred $41.3 million of its energy efficiency customer loan portfolio to two outside lenders in order to make additional loans to customers. CL&P remains the servicer of the loans and will transmit customer payments to the lenders. Under a three -year agreement with the lenders, additional energy efficiency loans will also be transferred with a maximum amount outstanding under this program of $55 million . The transaction did not qualify as a sale for accounting purposes, and the amounts of the loans are included in Accounts Receivable, Net and Other Long-Term Assets, and are offset by Other Current Liabilities and Other Long-Term Liabilities on CL&P’s balance sheet. The current and long-term portions totaled $16.5 million and $18.2 million , respectively, as of December 31, 2019 , and $18.5 million and $22.8 million , respectively, as of December 31, 2018 . H. Fuel, Materials, Supplies and REC Inventory Fuel, Materials, Supplies and REC Inventory include natural gas inventory, materials and supplies purchased primarily for construction or operation and maintenance purposes, and RECs. Inventory is valued at the lower of cost or net realizable value. RECs are purchased from suppliers of renewable sources of generation and are used to meet state mandated Renewable Portfolio Standards requirements. The carrying amounts of fuel, materials and supplies, and RECs, which are included in Current Assets on the balance sheets, were as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Fuel $ 26.7 $ — $ — $ — $ 33.1 $ — $ — $ — Materials and Supplies 132.9 50.7 54.7 18.5 126.1 44.5 48.6 24.3 RECs 75.9 — 69.4 6.5 78.8 — 65.6 13.2 Total $ 235.5 $ 50.7 $ 124.1 $ 25.0 $ 238.0 $ 44.5 $ 114.2 $ 37.5 Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases" or "normal sales" (normal) and to the marketable securities held in trusts. Fair value measurement guidance is also applied to valuations of the investments used to calculate the funded status of pension and PBOP plans, the nonrecurring fair value measurements of nonfinancial assets such as goodwill, long-lived assets and AROs. We also applied this guidance in the valuation of our basis differences in our equity method offshore wind investments (see Note 6, "Investments in Unconsolidated Affiliates," for further information). The fair value measurement guidance was also applied in estimating the fair value of preferred stock, long-term debt and RRBs. Fair Value Hierarchy: In measuring fair value, Eversource uses observable market data when available in order to minimize the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. Eversource evaluates the classification of assets and liabilities measured at fair value on a quarterly basis, and Eversource's policy is to recognize transfers between levels of the fair value hierarchy as of the end of the reporting period. The three levels of the fair value hierarchy are described below: Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable. Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products. Uncategorized - Investments that are measured at net asset value are not categorized within the fair value hierarchy. Determination of Fair Value: The valuation techniques and inputs used in Eversource's fair value measurements are described in Note 4, "Derivative Instruments," Note 5, "Marketable Securities," Note 6, "Investments in Unconsolidated Affiliates," Note 7, "Asset Retirement Obligations," Note 11A, "Employee Benefits – Pension Benefits and Postretirement Benefits Other Than Pension," Note 16, "Fair Value of Financial Instruments" and Note 25B, "Acquisition of Aquarion and Goodwill - Goodwill" to the financial statements. J. Derivative Accounting Many of the electric and natural gas companies' contracts for the purchase and sale of energy or energy-related products are derivatives. The accounting treatment for energy contracts entered into varies and depends on the intended use of the particular contract and on whether or not the contract is a derivative. The application of derivative accounting is complex and requires management judgment in the following respects: identification of derivatives and embedded derivatives, election and designation of a contract as normal, and determination of the fair value of derivative contracts. All of these judgments can have a significant impact on the financial statements. The judgment applied in the election of a contract as normal (and resulting accrual accounting) includes the conclusion that it is probable at the inception of the contract and throughout its term that it will result in physical delivery of the underlying product and that the quantities will be used or sold by the business in the normal course of business. If facts and circumstances change and management can no longer support this conclusion, then a contract cannot be considered normal, accrual accounting is terminated, and fair value accounting is applied prospectively. The fair value of derivative contracts is based upon the contract terms and conditions and the underlying market price or fair value per unit. When quantities are not specified in the contract, the Company determines whether the contract has a determinable quantity by using amounts referenced in default provisions and other relevant sections of the contract. The fair value of derivative assets and liabilities with the same counterparty are offset and recorded as a net derivative asset or liability on the balance sheets. Regulatory assets or regulatory liabilities are recorded to offset the fair values of derivative contracts related to energy and energy-related products, as contract settlements are recovered from, or refunded to, customers in future rates. All changes in the fair value of derivative contracts are recorded as regulatory assets or liabilities and do not impact net income. For further information regarding derivative contracts, see Note 4, "Derivative Instruments," to the financial statements. K. Operating Expenses Costs related to fuel and natural gas included in Purchased Power, Fuel and Transmission on the statements of income were as follows: For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Eversource - Natural Gas and Fuel $ 462.1 $ 442.6 $ 432.5 PSNH - Fuel — 7.9 43.4 PSNH completed the sale of its generation assets in 2018. See Note 14, "Generation Asset Sale," for further information. AFUDC represents the cost of borrowed and equity funds used to finance construction and is included in the cost of the electric, natural gas and water companies' utility plant on the balance sheet. The portion of AFUDC attributable to borrowed funds is recorded as a reduction of Interest Expense, and the AFUDC related to equity funds is recorded as Other Income, Net on the statements of income. AFUDC costs are recovered from customers over the service life of the related plant in the form of increased revenue collected as a result of higher depreciation expense. The average AFUDC rate is based on a FERC-prescribed formula using the cost of a company's short-term financings and capitalization (preferred stock, long-term debt and common equity), as appropriate. The average rate is applied to average eligible CWIP amounts to calculate AFUDC. AFUDC costs and the weighted-average AFUDC rates were as follows: Eversource For the Years Ended December 31, (Millions of Dollars, except percentages) 2019 2018 2017 Borrowed Funds $ 25.6 $ 19.7 $ 12.5 Equity Funds 45.0 44.0 34.4 Total AFUDC $ 70.6 $ 63.7 $ 46.9 Average AFUDC Rate 5.4 % 4.9 % 5.1 % For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars, except percentages) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Borrowed Funds $ 7.1 $ 10.4 $ 2.8 $ 6.3 $ 7.8 $ 1.3 $ 5.1 $ 4.8 $ 0.7 Equity Funds 13.2 19.8 3.4 12.2 15.6 — 12.1 10.2 — Total AFUDC $ 20.3 $ 30.2 $ 6.2 $ 18.5 $ 23.4 $ 1.3 $ 17.2 $ 15.0 $ 0.7 Average AFUDC Rate 6.3 % 5.7 % 4.6 % 5.8 % 5.0 % 0.7 % 6.2 % 5.0 % 0.7 % M. Other Income, Net The components of Other Income, Net on the statements of income were as follows: Eversource For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Pension, SERP and PBOP Non-Service Income Components $ 31.3 $ 60.8 $ 29.9 AFUDC Equity 45.0 44.0 34.4 Equity in Earnings of Unconsolidated Affiliates (1) 42.2 3.8 27.4 Investment Income/(Loss) 0.8 (4.0 ) 7.5 Interest Income (2) 12.8 18.1 8.3 Gains on Sales of Property 0.3 5.1 — Other 0.4 0.6 0.4 Total Other Income, Net $ 132.8 $ 128.4 $ 107.9 For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service Income Components $ 0.5 $ 23.5 $ 4.9 $ 9.5 $ 36.0 $ 9.9 $ 1.8 $ 19.2 $ 5.9 AFUDC Equity 13.2 19.8 3.4 12.2 15.6 — 12.1 10.2 — Equity in Earnings of Unconsolidated Affiliates 0.1 0.7 — 0.1 0.7 — — 0.3 — Investment Income/(Loss) 2.3 (0.4 ) 0.3 (3.0 ) (0.5 ) (0.8 ) 4.5 2.6 1.6 Interest Income (2) 1.5 0.7 10.5 3.7 0.8 14.1 4.6 1.8 2.2 Gains on Sales of Property — 0.1 — — 0.5 4.4 — — — Other (0.1 ) 0.2 0.1 0.2 — 0.1 — — 0.1 Total Other Income, Net $ 17.5 $ 44.6 $ 19.2 $ 22.7 $ 53.1 $ 27.7 $ 23.0 $ 34.1 $ 9.8 (1) Equity in earnings of unconsolidated affiliates includes an other-than-temporary impairment of $32.9 million of the Access Northeast project investment for the year ended December 31, 2018. See Note 6, "Investments in Unconsolidated Affiliates," for further information. Equity in earnings includes $20.4 million , $17.6 million and $9.7 million of pre-tax unrealized gains for the years ended December 31, 2019 , 2018 and 2017 , respectively, associated with an equity method investment in a renewable energy fund. (2) For the years ended December 31, 2019 and 2018, PSNH recognized $6.3 million and $8.7 million , respectively, of interest income for the equity return component of carrying charges on storm costs approved in 2019 and 2018. See Note 2, "Regulatory Accounting," for further information. N. Other Taxes Eversource's companies that serve customers in Connecticut collect gross receipts taxes levied by the state of Connecticut from their customers. These gross receipts taxes are recorded separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of income as follows: For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Eversource $ 163.1 $ 161.9 $ 157.4 CL&P 141.1 141.4 137.5 As agents for state and local governments, Eversource's companies that serve customers in Connecticut and Massachusetts collect certain sales taxes that are recorded on a net basis with no impact on the statements of income. Separate from above were amounts recorded as Taxes Other Than Income Taxes related to the remittance to the State of Connecticut of energy efficiency funds collected from customers in Operating Revenues. These amounts were $21.4 million and $46.8 million in 2019 and 2018, respectively. Energy efficiency funds collected from customers after July 1, 2019 are no longer subject to remittance to the State of Connecticut. These amounts were recorded separately, with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the Eversource and CL&P statements of income. O. Supplemental Cash Flow Information Eversource (Millions of Dollars) As of and For the Years Ended December 31, 2019 2018 2017 Cash Paid During the Year for: Interest, Net of Amounts Capitalized $ 532.4 $ 503.2 $ 419.1 Income Taxes 56.0 158.8 30.8 Non-Cash Investing Activities: Plant Additions Included in Accounts Payable (As of) (1) 379.4 389.3 379.5 As of and For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Cash Paid During the Year for: Interest, Net of Amounts Capitalized $ 144.6 $ 121.9 $ 56.9 $ 149.7 $ 122.1 $ 40.5 $ 144.6 $ 124.6 $ 45.9 Income Taxes 80.6 77.9 3.4 66.1 120.0 27.3 68.8 95.5 26.1 Non-Cash Investing Activities: Plant Additions Included in Accounts Payable (As of) (1) 111.3 116.4 49.9 106.1 116.5 35.1 132.5 116.5 44.4 (1) See Note 1B, "Summary of Significant Accounting Policies - Basis of Presentation," for information regarding the correction of non-cash capital additions at Eversource and PSNH reported as of December 31, 2018. Beginning in 2019, Eversource began issuing treasury shares to satisfy awards under the Company's incentive plans, shares issued under the dividend reinvestment and share purchase plan, and matching contributions under the Eversource 401k Plan. The issuance of treasury shares represents a non-cash transaction, as the treasury shares were used to fulfill Eversource's obligations that require the issuance of common shares. The following table reconciles cash as reported on the balance sheets to the cash and restricted cash balance as reported on the statements of cash flows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Cash as reported on the Balance Sheets $ 15.4 $ — $ 0.1 $ 0.4 $ 108.1 $ 87.7 $ 1.6 $ 1.4 Restricted cash included in: Special Deposits 52.5 4.6 6.2 32.5 72.1 3.5 13.0 47.5 Marketable Securities 46.0 0.4 — 0.6 25.9 0.4 0.1 0.6 Other Long-Term Assets 3.2 — — 3.2 3.2 — — 3.2 Cash and Restricted Cash reported on the Statements of Cash Flows $ 117.1 $ 5.0 $ 6.3 $ 36.7 $ 209.3 $ 91.6 $ 14.7 $ 52.7 Special Deposits represent cash collections related to the PSNH RRB customer charges that are held in trust and required ISO-NE cash deposits, and are included in Current Assets on the balance sheets. Restricted cash included in Marketable Securities represents money market funds held in trusts to fund certain non-qualified executive benefits and restricted trusts to fund CYAPC and YAEC's spent nuclear fuel storage obligations. P. Related Parties Eversource Service, Eversource's service company, provides centralized accounting, administrative, engineering, financial, information technology, legal, operational, planning, purchasing, tax, and other services to Eversource's companies. The Rocky River Realty Company, Renewable Properties, Inc. and Properties, Inc., three other Eversource subsidiaries, construct, acquire or lease some of the property and facilities used by Eversource's companies. As of both December 31, 2019 and 2018 , CL&P, NSTAR Electric and PSNH had long-term receivables from Eversource Service in the amounts of $25.0 million , $5.5 million and $3.8 million , respectively, which were included in Other Long-Term Assets on the balance sheets. These amounts related to the funding of investments held in trust by Eversource Service in connection with certain postretirement benefits for CL&P, NSTAR Electric and PSNH employees and have been eliminated in consolidation on the Eversource financial statements. Included in the CL&P, NSTAR Electric and PSNH balance sheets as of December 31, 2019 and 2018 were Accounts Receivable from Affiliated Companies and Accounts Payable to Affiliated Companies relating to transactions between CL&P, NSTAR Electric and PSNH and other subsidiaries that are wholly-owned by Eversource. These amounts have been eliminated in consolidation on the Eversource financial statements. Q. Acquisition of Assets of Columbia Gas of Massachusetts On February 26, 2020, Eversource and NiSource entered into an asset purchase agreement (the Agreement) pursuant to which Eversource would acquire the assets that comprise NiSource’s local gas distribution business in Massachusetts, which is doing business as Columbia Gas of Massachusetts (CMA). The purchase price of $1.1 billion includes a target working capital amount that would be adjusted to reflect actual working capital as of the closing date. The acquisition and resulting rate plan both require DPU and other approvals.

REGULATORY ACCOUNTING

REGULATORY ACCOUNTING	12 Months Ended
REGULATORY ACCOUNTING	Dec. 31, 2019
Regulated Operations [Abstract]
REGULATORY ACCOUNTING	REGULATORY ACCOUNTING Eversource's utility companies are subject to rate regulation that is based on cost recovery and meets the criteria for application of accounting guidance for rate-regulated operations, which considers the effect of regulation on the timing of the recognition of certain revenues and expenses. The regulated companies' financial statements reflect the effects of the rate-making process. The rates charged to the customers of Eversource's regulated companies are designed to collect each company's costs to provide service, plus a return on investment. The application of accounting guidance for rate-regulated enterprises results in recording regulatory assets and liabilities. Regulatory assets represent the deferral of incurred costs that are probable of future recovery in customer rates. Regulatory assets are amortized as the incurred costs are recovered through customer rates. Regulatory liabilities represent either revenues received from customers to fund expected costs that have not yet been incurred or probable future refunds to customers. Management believes it is probable that each of the regulated companies will recover its respective investments in long-lived assets, including regulatory assets. If management were to determine that it could no longer apply the accounting guidance applicable to rate-regulated enterprises to any of the regulated companies' operations, or if management could not conclude it is probable that costs would be recovered from customers in future rates, the costs would be charged to net income in the period in which the determination is made. Regulatory Assets: The components of regulatory assets were as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Benefit Costs $ 2,382.9 $ 539.0 $ 629.8 $ 218.2 $ 1,914.8 $ 424.7 $ 544.4 $ 169.6 Income Taxes, Net 725.8 458.8 108.0 12.8 728.6 454.4 105.9 8.3 Securitized Stranded Costs 565.3 — — 565.3 608.4 — — 608.4 Storm Restoration Costs, Net 540.6 274.6 200.6 65.4 576.0 302.6 212.9 60.5 Regulatory Tracker Mechanisms 411.5 78.3 207.1 65.8 316.0 33.2 169.1 67.3 Derivative Liabilities 334.5 329.2 — — 356.5 356.5 — — Goodwill-related 331.5 — 284.6 — 348.4 — 299.1 — Asset Retirement Obligations 97.2 30.8 50.3 3.6 89.2 32.3 42.2 3.3 Other Regulatory Assets 125.4 25.2 55.2 14.7 208.0 27.0 64.6 12.1 Total Regulatory Assets 5,514.7 1,735.9 1,535.6 945.8 5,145.9 1,630.7 1,438.2 929.5 Less: Current Portion 651.1 178.6 285.6 84.1 514.8 125.2 241.7 67.2 Total Long-Term Regulatory Assets $ 4,863.6 $ 1,557.3 $ 1,250.0 $ 861.7 $ 4,631.1 $ 1,505.5 $ 1,196.5 $ 862.3 Benefit Costs: Eversource's Pension, SERP and PBOP Plans are accounted for in accordance with accounting guidance on defined benefit pension and other PBOP plans. The liability (or asset) recorded by the regulated companies to recognize the funded status of their retiree benefit plans is offset by a regulatory asset (or offset by a regulatory liability in the case of a benefit plan asset) in lieu of a charge to Accumulated Other Comprehensive Income/(Loss), reflecting ultimate recovery from customers through rates. The regulatory asset (or regulatory liability) is amortized as the actuarial gains and losses and prior service cost are amortized to net periodic benefit cost for the pension and PBOP plans. All amounts are remeasured annually. Regulatory accounting is also applied to the portions of Eversource's service company costs that support the regulated companies, as these amounts are also recoverable. As these regulatory assets or regulatory liabilities do not represent a cash outlay for the regulated companies, no carrying charge is recovered from customers. See Note 11A, "Employee Benefits - Pensions and Postretirement Benefits Other Than Pension," for further information on regulatory benefit plan amounts recognized and amortized during the year. CL&P, NSTAR Electric and PSNH recover benefit costs related to their distribution and transmission operations from customers in rates as allowed by their applicable regulatory commissions. NSTAR Electric recovers qualified pension and PBOP expenses related to its distribution operations through a rate reconciling mechanism that fully tracks the change in net pension and PBOP expenses each year. Income Taxes, Net: The tax effect of temporary book-tax differences (differences between the periods in which transactions affect income in the financial statements and the periods in which they affect the determination of taxable income, including those differences relating to uncertain tax positions) is accounted for in accordance with the rate-making treatment of the applicable regulatory commissions and accounting guidance for income taxes. Differences in income taxes between the accounting guidance and the rate-making treatment of the applicable regulatory commissions are recorded as regulatory assets. As these assets are offset by deferred income tax liabilities, no carrying charge is collected. The amortization period of these assets varies depending on the nature and/or remaining life of the underlying assets and liabilities. For further information regarding income taxes, see Note 12, "Income Taxes," to the financial statements. Securitized Stranded Costs: In 2018, a subsidiary of PSNH issued $635.7 million of securitized RRBs to finance PSNH's unrecovered remaining costs associated with the divestiture of its generation assets. Securitized regulatory assets, which are not earning an equity return, are being recovered over the amortization period of the associated RRBs. The PSNH RRBs are expected to be repaid by February 1, 2033. For further information, see Note 10, "Rate Reduction Bonds and Variable Interest Entities." Storm Restoration Costs, Net: The storm restoration cost deferrals relate to costs incurred for storm events at CL&P, NSTAR Electric and PSNH that each company expects to recover from customers. A storm must meet certain criteria to qualify for deferral and recovery with the criteria specific to each state jurisdiction and utility company. Once a storm qualifies for recovery, all qualifying expenses incurred during storm restoration efforts are deferred and recovered from customers. Costs for storms that do not meet the specific criteria are expensed as incurred. In addition to storm restoration costs, CL&P and PSNH are each allowed to recover pre-staging storm costs. Management believes storm restoration costs deferred were prudently incurred and meet the criteria for specific cost recovery in Connecticut, Massachusetts and New Hampshire, and that recovery from customers is probable through the applicable regulatory recovery processes. Each electric utility company either recovers a carrying charge on its deferred storm restoration cost regulatory asset balance or the regulatory asset balance is included in rate base. In 2019, several significant storms caused extensive damage to our electric distribution systems and customer outages. These storms resulted in deferred storm restoration costs of approximately $126 million ( $62 million for CL&P, $48 million for NSTAR Electric, and $16 million for PSNH), which were reflected in Storm Restoration Costs, Net in the table above as of December 31, 2019 . Storm Filings: On November 16, 2018, CL&P filed for recovery of $153 million of storm costs incurred from October 2017 through May 2018, with recovery over six years . Through the course of the proceeding, CL&P updated its request to $145.5 million to reflect final invoicing and capitalization amounts. On April 17, 2019, PURA authorized recovery of $141.0 million as part of storm cost recovery and the remainder to be recorded to plant or other balance sheet accounts. CL&P began recovery of the $141.0 million in distribution rates effective May 1, 2019. On March 26, 2019, the NHPUC approved the recovery of $38.1 million , plus carrying charges, of storm costs incurred from December 2013 through April 2016 and the transfer of funding from PSNH’s major storm reserve to recover those costs. The costs of these storms (excluding the equity return component of the carrying charges) were deferred as regulatory assets, and the funding reserve collected from customers was accrued as a regulatory liability. As a result of the duration of time between incurring storm costs in December 2013 through April 2016 and final approval from the NHPUC in 2019, PSNH recognized $5.2 million (pre-tax) for the equity return component of the carrying charges within Other Income, Net on the statement of income in 2019, which has been collected from customers. Also included in the March 26, 2019 NHPUC approval is a prospective requirement for PSNH to annually net its storm funding reserve collected from customers against deferred storm costs. In addition, on June 27, 2019, the NHPUC approved a temporary rate settlement that allowed PSNH to recover approximately $68.5 million in unrecovered storm costs over a five-year period beginning August 1, 2019, with debt carrying charges. Regulatory Tracker Mechanisms: The regulated companies' approved rates are designed to recover costs incurred to provide service to customers. The regulated companies recover certain of their costs on a fully-reconciling basis through regulatory commission-approved tracking mechanisms. The differences between the costs incurred (or the rate recovery allowed) and the actual revenues are recorded as regulatory assets (for undercollections) or as regulatory liabilities (for overcollections) to be included in future customer rates each year. Carrying charges are recovered in rates on all material regulatory tracker mechanisms. CL&P, NSTAR Electric and PSNH each recover, on a fully reconciling basis, the costs associated with the procurement of energy, transmission related costs from FERC-approved transmission tariffs, energy efficiency programs, low income assistance programs, certain uncollectible accounts receivable for hardship customers, and restructuring and stranded costs as a result of deregulation (including securitized RRB charges), and additionally for the Massachusetts utilities, pension and PBOP benefits and net metering for distributed generation. Energy procurement costs at NSTAR Electric include the costs related to its solar power facilities. CL&P, NSTAR Electric, Yankee Gas and NSTAR Gas each have a regulatory commission approved revenue decoupling mechanism. Distribution revenues are decoupled from customer sales volumes, where applicable, which breaks the relationship between sales volumes and revenues. Each company reconciles its annual base distribution rate recovery amount to the pre-established levels of baseline distribution delivery service revenues. Any difference between the allowed level of distribution revenue and the actual amount realized during a 12-month period is adjusted through rates in the following period. Derivative Liabilities: Regulatory assets are recorded as an offset to derivative liabilities and relate to the fair value of contracts used to purchase energy and energy-related products that will be recovered from customers in future rates. These assets are excluded from rate base and are being recovered as the actual settlements occur over the duration of the contracts. See Note 4, "Derivative Instruments," to the financial statements for further information on these contracts. Goodwill-related: The goodwill regulatory asset originated from a 1999 transaction, and the DPU allowed its recovery in NSTAR Electric and NSTAR Gas rates. This regulatory asset is currently being amortized and recovered from customers in rates without a carrying charge over a 40 -year period, and as of December 31, 2019 , there were 20 years of amortization remaining. Asset Retirement Obligations: The costs associated with the depreciation of the regulated companies' ARO assets and accretion of the ARO liabilities are recorded as regulatory assets in accordance with regulatory accounting guidance. The regulated companies' ARO assets, regulatory assets and liabilities offset and are excluded from rate base. These costs are being recovered over the life of the underlying property, plant and equipment. Other Regulatory Assets: Other Regulatory Assets primarily include contractual obligations associated with the spent nuclear fuel storage costs of the CYAPC, YAEC and MYAPC decommissioned nuclear power facilities, environmental remediation costs, losses associated with the reacquisition or redemption of long-term debt, certain uncollectible accounts receivable for hardship customers, certain merger-related costs allowed for recovery, water tank painting costs, and various other items. Regulatory Costs in Long-Term Assets: Eversource's regulated companies had $146.0 million (including $51.8 million for CL&P, $55.7 million for NSTAR Electric and $18.0 million for PSNH) and $122.9 million (including $42.1 million for CL&P, $49.3 million for NSTAR Electric and $12.2 million for PSNH) of additional regulatory costs as of December 31, 2019 and 2018 , respectively, that were included in long-term assets on the balance sheets. These amounts represent incurred costs for which recovery has not yet been specifically approved by the applicable regulatory agency. However, based on regulatory policies or past precedent on similar costs, management believes it is probable that these costs will ultimately be approved and recovered from customers in rates. Equity Return on Regulatory Assets: For rate-making purposes, the regulated companies recover the carrying costs related to their regulatory assets. For certain regulatory assets, the carrying cost recovered includes an equity return component. This equity return, which is not recorded on the balance sheets, totaled $0.5 million and $0.7 million for CL&P as of December 31, 2019 and 2018 , respectively, and $6.5 million and $12.0 million for PSNH as of December 31, 2019 and 2018 , respectively. These carrying costs will be recovered from customers in future rates. Regulatory Liabilities: The components of regulatory liabilities were as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH EDIT due to Tax Cuts and Jobs Act $ 2,844.6 $ 1,022.8 $ 1,071.2 $ 392.8 $ 2,883.0 $ 1,031.0 $ 1,103.7 $ 396.4 Cost of Removal 559.8 64.6 330.6 16.3 521.0 39.9 307.1 22.1 Benefit Costs 84.5 — 72.2 — 91.2 — 76.9 — Regulatory Tracker Mechanisms 325.1 94.8 165.6 57.0 309.0 89.5 163.7 48.3 AFUDC - Transmission 73.2 46.0 27.2 — 70.7 47.4 23.3 — Revenue Subject to Refund due to Tax Cuts and Jobs Act 14.6 — — 6.0 24.6 — — 12.6 Other Regulatory Liabilities 117.4 19.6 59.0 7.1 80.2 24.0 29.2 4.2 Total Regulatory Liabilities 4,019.2 1,247.8 1,725.8 479.2 3,979.7 1,231.8 1,703.9 483.6 Less: Current Portion 361.2 82.8 209.2 65.8 370.2 109.6 190.6 55.5 Total Long-Term Regulatory Liabilities $ 3,658.0 $ 1,165.0 $ 1,516.6 $ 413.4 $ 3,609.5 $ 1,122.2 $ 1,513.3 $ 428.1 EDIT due to Tax Cuts and Jobs Act: Pursuant to the "Tax Cuts and Jobs Act" (the Act), which became law on December 22, 2017, Eversource had remeasured its existing deferred federal income tax balances to reflect the decrease in the U.S. federal corporate income tax rate from 35 percent to 21 percent. The remeasurement resulted in provisional regulated excess accumulated deferred income tax (excess ADIT or EDIT) liabilities that will benefit our customers in future periods and were recognized as regulatory liabilities on the balance sheet. EDIT liabilities related to property, plant, and equipment are subject to IRS normalization rules and will be returned to customers using the same timing as the remaining useful lives of the underlying assets that gave rise to the ADIT liabilities. Eversource's regulated companies are in the process of, or will be, refunding the EDIT liabilities to customers based on orders issued by applicable state regulatory commissions. For CL&P (effective May 1, 2019) and Yankee Gas (effective November 15, 2018), the refund of EDIT liabilities was incorporated into base distribution rates. For NSTAR Electric (effective January 1, 2019) and NSTAR Gas (effective February 1, 2019), the refund of EDIT liabilities occurred in rates through a new reconciling factor. For PSNH, EDIT refunds will be addressed as part of the permanent distribution rate case filing. The EDIT balance related to PSNH's divested generation assets was included as a component of the securitization of the stranded generation assets and began to be refunded to customers, effective August 1, 2018. For our transmission companies, on November 21, 2019, the FERC issued its final rule requiring public utilities with transmission formula rates to make adjustments to ADIT and EDIT. Eversource expects to submit a filing demonstrating its compliance with the final rule in the second half of 2020. Cost of Removal: Eversource's regulated companies currently recover amounts in rates for future costs of removal of plant assets over the lives of the assets. The estimated cost to remove utility assets from service is recognized as a component of depreciation expense, and the cumulative amount collected from customers but not yet expended is recognized as a regulatory liability. AFUDC - Transmission: Regulatory liabilities were recorded by CL&P and NSTAR Electric for AFUDC accrued on certain reliability-related transmission projects to reflect local rate base recovery. These regulatory liabilities will be amortized over the depreciable life of the related transmission assets. Revenue Subject to Refund due to Tax Cuts and Jobs Act: Eversource established a regulatory liability with a corresponding reduction to revenue, to reflect the difference between the 35 percent federal corporate income tax rate included in rates charged to customers and the 21 percent federal corporate income tax rate, effective January 1, 2018 as a result of the Tax Cuts and Jobs Act, until rates billed to customers reflected the lower federal tax rate. Effective May 1, 2018, CL&P adjusted distribution rates billed to customers to reflect the lower federal income tax rate prospectively and, as of December 31, 2018, fully refunded its regulatory liability associated with the higher federal corporate income tax rate billed to customers in the period between January 1, 2018 through April 30, 2018. Effective November 15, 2018, Yankee Gas adjusted distribution rates to reflect the lower federal income tax rate prospectively and to refund its regulatory liability associated with the higher federal corporate income tax rate billed to customers in the period between January 1, 2018 through November 14, 2018. Effective July 1, 2019, PSNH adjusted temporary distribution rates to reflect the lower federal income tax rate prospectively and to refund its regulatory liability associated with the higher federal corporate income tax rate billed to customers in the period between January 1, 2018 through June 30, 2019. For NSTAR Electric and NSTAR Gas, a December 2018 DPU order indicated that the DPU would not require a revision to base distribution rates for any potential refunds associated with the higher federal corporate income tax rate billed to customers in the period between January 1, 2018 to the effective dates of each company's rate changes (effective February 1, 2018 for NSTAR Electric and July 1, 2018 for NSTAR Gas). Effective January 1, 2018, local transmission service rates were updated to reflect the lower U.S. federal corporate income tax rate that resulted from the act. On June 28, 2018, FERC granted a one-time tariff waiver of tariff provisions related to the federal corporate income tax rate so that effective June 1, 2018, the regional transmission service rates also reflected the reduced federal corporate income tax rate at 21 percent. FERC ROE Complaints : As of December 31, 2019 , Eversource has a reserve established for the second ROE complaint in the pending FERC ROE complaint proceedings, which was recorded as a regulatory liability and is reflected within Regulatory Tracker Mechanisms in the table above. The cumulative pre-tax reserve (excluding interest) as of December 31, 2019 totaled $39.1 million for Eversource (including $21.4 million for CL&P, $14.6 million for NSTAR Electric and $3.1 million for PSNH). See Note 13E, "Commitments and Contingencies – FERC ROE Complaints," for further information on developments in the pending ROE complaint proceedings.

PROPERTY, PLANT AND EQUIPMENT A

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	12 Months Ended
PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION Utility property, plant and equipment is recorded at original cost. Original cost includes materials, labor, construction overheads and AFUDC for regulated property. The cost of repairs and maintenance is charged to Operations and Maintenance expense as incurred. The following tables summarize property, plant and equipment by asset category: Eversource As of December 31, (Millions of Dollars) 2019 2018 Distribution - Electric $ 15,880.0 $ 15,071.1 Distribution - Natural Gas 3,931.1 3,546.2 Transmission - Electric 10,958.4 10,153.9 Distribution - Water 1,726.5 1,639.8 Solar 200.2 164.1 Utility 32,696.2 30,575.1 Other (1) 1,025.6 778.6 Property, Plant and Equipment, Gross 33,721.8 31,353.7 Less: Accumulated Depreciation Utility (7,483.5 ) (7,126.2 ) Other (387.4 ) (336.7 ) Total Accumulated Depreciation (7,870.9 ) (7,462.9 ) Property, Plant and Equipment, Net 25,850.9 23,890.8 Construction Work in Progress 1,734.6 1,719.6 Total Property, Plant and Equipment, Net $ 27,585.5 $ 25,610.4 As of December 31, 2019 2018 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Distribution - Electric $ 6,485.5 $ 7,163.7 $ 2,271.1 $ 6,176.4 $ 6,756.4 $ 2,178.6 Transmission - Electric 5,043.0 4,411.9 1,498.7 4,700.5 4,065.9 1,338.7 Solar — 200.2 — — 164.1 — Property, Plant and Equipment, Gross 11,528.5 11,775.8 3,769.8 10,876.9 10,986.4 3,517.3 Less: Accumulated Depreciation (2,385.7 ) (2,895.3 ) (799.9 ) (2,302.6 ) (2,702.0 ) (772.9 ) Property, Plant and Equipment, Net 9,142.8 8,880.5 2,969.9 8,574.3 8,284.4 2,744.4 Construction Work in Progress 483.0 592.3 159.6 335.4 510.3 135.7 Total Property, Plant and Equipment, Net $ 9,625.8 $ 9,472.8 $ 3,129.5 $ 8,909.7 $ 8,794.7 $ 2,880.1 (1) These assets are primarily comprised of computer software, hardware and equipment at Eversource Service and buildings at The Rocky River Realty Company. In 2019, Eversource recorded an impairment charge for the NPT project costs, which had been recorded within both Construction Work in Progress and the Transmission - Electric asset categories. For further information regarding the impairment of NPT, see Note 1D, "Summary of Significant Accounting Policies - Impairment of Northern Pass Transmission," to the financial statements. Depreciation of utility assets is calculated on a straight-line basis using composite rates based on the estimated remaining useful lives of the various classes of property (estimated useful life for PSNH distribution and the water utilities). The composite rates, which are subject to approval by the appropriate state regulatory agency, include a cost of removal component, which is collected from customers over the lives of the plant assets and is recognized as a regulatory liability. Depreciation rates are applied to property from the time it is placed in service. Upon retirement from service, the cost of the utility asset is charged to the accumulated provision for depreciation. The actual incurred removal costs are applied against the related regulatory liability. The depreciation rates for the various classes of utility property, plant and equipment aggregate to composite rates as follows: (Percent) 2019 2018 2017 Eversource 3.0 % 2.9 % 3.0 % CL&P 2.8 % 2.8 % 2.8 % NSTAR Electric 2.8 % 2.8 % 2.9 % PSNH 2.8 % 2.8 % 3.1 % The following table summarizes average remaining useful lives of depreciable assets: As of December 31, 2019 (Years) Eversource CL&P NSTAR Electric PSNH Distribution - Electric 34.3 35.3 33.7 33.2 Distribution - Natural Gas 43.2 — — — Transmission - Electric 40.4 36.8 44.9 42.1 Distribution - Water 33.5 — — — Solar 24.2 — 24.2 — Other (1) 11.2 — — — (1) The estimated useful life of computer software, hardware and equipment primarily ranges from 5 to 15 years and of buildings is 40 years .

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	12 Months Ended
DERIVATIVE INSTRUMENTS	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS	DERIVATIVE INSTRUMENTS The electric and natural gas companies purchase and procure energy and energy-related products, which are subject to price volatility, for their customers. The costs associated with supplying energy to customers are recoverable from customers in future rates. These regulated companies manage the risks associated with the price volatility of energy and energy-related products through the use of derivative and non-derivative contracts. Many of the derivative contracts meet the definition of, and are designated as, normal and qualify for accrual accounting under the applicable accounting guidance. The costs and benefits of derivative contracts that meet the definition of normal are recognized in Operating Expenses on the statements of income, as applicable, as electricity or natural gas is delivered. Derivative contracts that are not designated as normal are recorded at fair value as current or long-term Derivative Assets or Derivative Liabilities on the balance sheets. For the electric and natural gas companies, regulatory assets or regulatory liabilities are recorded to offset the fair values of derivatives, as contract settlement amounts are recovered from, or refunded to, customers in their respective energy supply rates. The gross fair values of derivative assets and liabilities with the same counterparty are offset and reported as net Derivative Assets or Derivative Liabilities, with current and long-term portions, on the balance sheets. The following table presents the gross fair values of contracts, categorized by risk type, and the net amounts recorded as current or long-term derivative assets or liabilities: As of December 31, 2019 2018 (Millions of Dollars) Fair Value Hierarchy Commodity Supply and Price Risk Management Netting (1) Net Amount Recorded as a Derivative Commodity Supply and Price Risk Management Netting (1) Net Amount Recorded as a Derivative Current Derivative Assets: CL&P Level 3 $ 12.2 $ (0.4 ) $ 11.8 $ 9.6 $ (3.4 ) $ 6.2 Other Level 2 — — — 1.5 (0.9 ) 0.6 Long-Term Derivative Assets: CL&P Level 3 67.5 (2.1 ) 65.4 74.2 (2.3 ) 71.9 Current Derivative Liabilities: CL&P Level 3 (67.8 ) — (67.8 ) (55.1 ) — (55.1 ) Other Level 2 (5.2 ) — (5.2 ) — — — Long-Term Derivative Liabilities : CL&P Level 3 (338.6 ) — (338.6 ) (379.5 ) — (379.5 ) Other Level 2 (0.1 ) — (0.1 ) — — — (1) Amounts represent derivative assets and liabilities that Eversource elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists. The business activities that result in the recognition of derivative assets also create exposure to various counterparties. As of December 31, 2019 , CL&P's derivative assets were exposed to counterparty credit risk and contracted with investment grade entities. For further information on the fair value of derivative contracts, see Note 1I, "Summary of Significant Accounting Policies – Fair Value Measurements," and Note 1J, "Summary of Significant Accounting Policies – Derivative Accounting," to the financial statements. Derivative Contracts at Fair Value with Offsetting Regulatory Amounts Commodity Supply and Price Risk Management : As required by regulation, CL&P, along with UI, has capacity-related contracts with generation facilities. CL&P has a sharing agreement with UI, with 80 percent of the costs or benefits of each contract borne by or allocated to CL&P and 20 percent borne by or allocated to UI. The combined capacities of these contracts as of December 31, 2019 and 2018 were 676 MW and 787 MW, respectively. The capacity contracts extend through 2026 and obligate both CL&P and UI to make or receive payments on a monthly basis to or from the generation facilities based on the difference between a set capacity price and the capacity market price received in the ISO-NE capacity markets. In addition, CL&P has a contract to purchase 0.1 million MWh of energy per year through 2020. As of December 31, 2019 and 2018 , Eversource had New York Mercantile Exchange (NYMEX) financial contracts for natural gas futures in order to reduce variability associated with the price of 9.6 million and 12.5 million MMBtu of natural gas, respectively. For the years ended December 31, 2019 , 2018 and 2017 , there were losses of $20.7 million , $25.0 million and $29.0 million , respectively, deferred as regulatory costs, which reflect the change in fair value associated with Eversource's derivative contracts. Fair Value Measurements of Derivative Instruments Derivative contracts classified as Level 2 in the fair value hierarchy relate to the financial contracts for natural gas futures. Prices are obtained from broker quotes and are based on actual market activity. The contracts are valued using NYMEX natural gas prices. Valuations of these contracts also incorporate discount rates using the yield curve approach. The fair value of derivative contracts classified as Level 3 utilizes significant unobservable inputs. The fair value is modeled using income techniques, such as discounted cash flow valuations adjusted for assumptions related to exit price. Significant observable inputs for valuations of these contracts include energy and energy-related product prices in future years for which quoted prices in an active market exist. Fair value measurements categorized in Level 3 of the fair value hierarchy are prepared by individuals with expertise in valuation techniques, pricing of energy and energy-related products, and accounting requirements. The future capacity prices for periods that are not quoted in an active market or established at auction are based on available market data and are escalated based on estimates of inflation in order to address the full term of the contract. Valuations of derivative contracts using a discounted cash flow methodology include assumptions regarding the timing and likelihood of scheduled payments and also reflect non-performance risk, including credit, using the default probability approach based on the counterparty's credit rating for assets and the Company's credit rating for liabilities. Valuations incorporate estimates of premiums or discounts that would be required by a market participant to arrive at an exit price, using historical market transactions adjusted for the terms of the contract. The following is a summary of Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts: As of December 31, 2019 2018 CL&P Range Period Covered Range Period Covered Capacity Prices $ 3.01 — 7.34 per kW-Month 2023 - 2026 $ 4.30 — 7.44 per kW-Month 2022 - 2026 Forward Reserve 0.80 — 1.90 per kW-Month 2020 - 2024 0.75 — 1.78 per kW-Month 2019 - 2024 Exit price premiums of 2.1 percent through 13.6 percent are also applied to these contracts and reflect the uncertainty and illiquidity premiums that would be required based on the most recent market activity available for similar type contracts. Significant increases or decreases in future capacity or forward reserve prices in isolation would decrease or increase, respectively, the fair value of the derivative liability. Any increases in risk premiums would increase the fair value of the derivative liability. Changes in these fair values are recorded as a regulatory asset or liability and do not impact net income. Valuations using significant unobservable inputs: The following table presents changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis. CL&P (Millions of Dollars) For the Years Ended December 31, 2019 2018 Derivatives, Net: Fair Value as of Beginning of Period $ (356.5 ) $ (362.3 ) Net Realized/Unrealized Losses Included in Regulatory Assets (15.0 ) (32.0 ) Settlements 42.3 37.8 Fair Value as of End of Period $ (329.2 ) $ (356.5 )

MARKETABLE SECURITIES

MARKETABLE SECURITIES	12 Months Ended
MARKETABLE SECURITIES	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
MARKETABLE SECURITIES	MARKETABLE SECURITIES Eversource holds marketable securities that are primarily used to fund certain non-qualified executive benefits. The trusts that hold marketable securities are not subject to regulatory oversight by state or federal agencies. CYAPC and YAEC maintain legally restricted trusts, each of which holds marketable securities, to fund the spent nuclear fuel removal obligations of their nuclear fuel storage facilities. Equity Securities: Unrealized gains and losses on equity securities held in Eversource's non-qualified executive benefit trust are recorded in Other Income, Net on the statements of income. The fair value of these equity securities as of December 31, 2019 and 2018 was $ 45.7 million and $44.0 million , respectively. For the years ended December 31, 2019 and 2018, there were unrealized gains of $9.8 million and unrealized losses of $4.3 million recorded in Other Income, Net related to these equity securities, respectively. Eversource's equity securities also include CYAPC's and YAEC's marketable securities held in spent nuclear fuel trusts, which had fair values of $ 182.8 million and $200.0 million as of December 31, 2019 and 2018 , respectively. Unrealized gains and losses for these spent nuclear fuel trusts are subject to regulatory accounting treatment and are recorded in Marketable Securities with the corresponding offset to Other Long-Term Liabilities on the balance sheets, with no impact on the statements of income. Available-for-Sale Debt Securities: The following is a summary of the available-for-sale debt securities, which are recorded at fair value and are included in current and long-term Marketable Securities on the balance sheets. As of December 31, 2019 2018 Eversource (Millions of Dollars) Amortized Pre-Tax Pre-Tax Fair Value Amortized Pre-Tax Pre-Tax Fair Value Debt Securities $ 228.4 $ 5.8 $ (0.1 ) $ 234.1 $ 190.0 $ 0.4 $ (4.0 ) $ 186.4 Eversource's debt securities include CYAPC's and YAEC's marketable securities held in spent nuclear fuel trusts in the amounts of $198.1 million and $143.9 million as of December 31, 2019 and 2018 , respectively. Unrealized gains and losses on available-for-sale debt securities held in Eversource's non-qualified benefit trust are recorded in Accumulated Other Comprehensive Income. There have been no significant unrealized losses, other-than-temporary impairments, or credit losses for the years ended December 31, 2019 or 2018 . Factors considered in determining whether a credit loss exists include the duration and severity of the impairment, adverse conditions specifically affecting the issuer, and the payment history, ratings and rating changes of the security. For asset-backed debt securities, underlying collateral and expected future cash flows are also evaluated. As of December 31, 2019 , the contractual maturities of available-for-sale debt securities were as follows: Eversource (Millions of Dollars) Amortized Cost Fair Value Less than one year (1) $ 59.2 $ 59.3 One to five years 40.5 41.4 Six to ten years 33.6 34.8 Greater than ten years 95.1 98.6 Total Debt Securities $ 228.4 $ 234.1 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC spent nuclear fuel trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets. Realized Gains and Losses: Realized gains and losses are recorded in Other Income, Net for Eversource's benefit trust and are offset in Other Long-Term Liabilities for CYAPC and YAEC. Eversource utilizes the specific identification basis method for the Eversource non-qualified benefit trust, and the average cost basis method for the CYAPC and YAEC spent nuclear fuel trusts to compute the realized gains and losses on the sale of marketable securities. Fair Value Measurements: The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Eversource (Millions of Dollars) As of December 31, 2019 2018 Level 1: Mutual Funds and Equities $ 228.5 $ 244.0 Money Market Funds 46.0 25.9 Total Level 1 $ 274.5 $ 269.9 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 96.8 $ 79.6 Corporate Debt Securities 44.0 39.5 Asset-Backed Debt Securities 12.9 14.0 Municipal Bonds 26.7 19.2 Other Fixed Income Securities 7.7 8.2 Total Level 2 $ 188.1 $ 160.5 Total Marketable Securities $ 462.6 $ 430.4 U.S. government issued debt securities are valued using market approaches that incorporate transactions for the same or similar bonds and adjustments for yields and maturity dates. Corporate debt securities are valued using a market approach, utilizing recent trades of the same or similar instruments and also incorporating yield curves, credit spreads and specific bond terms and conditions. Asset-backed debt securities include collateralized mortgage obligations, commercial mortgage backed securities, and securities collateralized by auto loans, credit card loans or receivables. Asset-backed debt securities are valued using recent trades of similar instruments, prepayment assumptions, yield curves, issuance and maturity dates, and tranche information. Municipal bonds are valued using a market approach that incorporates reported trades and benchmark yields. Other fixed income securities are valued using pricing models, quoted prices of securities with similar characteristics, and discounted cash flows.

ASSET RETIREMENT OBLIGATIONS

ASSET RETIREMENT OBLIGATIONS	12 Months Ended
ASSET RETIREMENT OBLIGATIONS	Dec. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]
ASSET RETIREMENT OBLIGATIONS	ASSET RETIREMENT OBLIGATIONS Eversource, including CL&P, NSTAR Electric and PSNH, recognizes a liability for the fair value of an ARO on the obligation date if the liability's fair value can be reasonably estimated, even if it is conditional on a future event. Settlement dates and future costs are reasonably estimated when sufficient information becomes available. Management has identified various categories of AROs, primarily CYAPC's and YAEC's obligation to dispose of spent nuclear fuel and high level waste, and also certain assets containing asbestos and hazardous contamination. Management has performed fair value calculations reflecting expected probabilities for settlement scenarios. The fair value of an ARO is recorded as a liability in Other Long-Term Liabilities with a corresponding amount included in Property, Plant and Equipment, Net on the balance sheets. The ARO assets are depreciated, and the ARO liabilities are accreted over the estimated life of the obligation and the corresponding credits are recorded as accumulated depreciation and ARO liabilities, respectively. As the electric and natural gas companies are rate-regulated on a cost-of-service basis, these companies apply regulatory accounting guidance and both the depreciation and accretion costs associated with these companies' AROs are recorded as increases to Regulatory Assets on the balance sheets. A reconciliation of the beginning and ending carrying amounts of ARO liabilities is as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Balance as of Beginning of Year $ 466.2 $ 33.5 $ 72.4 $ 4.0 $ 419.1 $ 31.5 $ 44.6 $ 25.0 Liabilities Incurred During the Year 30.3 — 30.3 — 11.3 — 11.3 — Liabilities Settled During the Year (21.3 ) (3.6 ) — — (36.6 ) — — (21.5 ) Accretion 27.1 2.2 3.5 0.2 25.5 2.0 2.2 0.5 Revisions in Estimated Cash Flows (12.8 ) (0.1 ) (8.7 ) — 46.9 — 14.3 — Balance as of End of Year $ 489.5 $ 32.0 $ 97.5 $ 4.2 $ 466.2 $ 33.5 $ 72.4 $ 4.0 The ARO balance includes the current portion of $1.0 million for Eversource and NSTAR Electric as of December 31, 2019 , which is included in Other Current Liabilities on the balance sheets. Eversource's amounts include CYAPC and YAEC's AROs of $337.7 million and $339.9 million as of December 31, 2019 and 2018 , respectively. The fair value of the ARO for CYAPC and YAEC includes uncertainties of the fuel off-load dates related to the DOE's timing of performance regarding its obligation to dispose of the spent nuclear fuel and high level waste and other assumptions, including discount rates. The incremental asset recorded as an offset to the ARO liability was fully depreciated since the plants have no remaining useful life. Any changes in the ARO liability are recorded with a corresponding offset to the related regulatory asset. The assets held in the CYAPC and YAEC spent nuclear fuel trusts are restricted for settling the ARO and all other nuclear fuel storage obligations. For further information on the assets held in the spent nuclear fuel trusts, see Note 5, "Marketable Securities," to the financial statements. The increase in the ARO balance at NSTAR Electric for the year ended December 31, 2019 was due to the recording of a new liability associated with the installation of a 115 kV distribution cable across Boston Harbor to Deer Island that was placed into service in 2019. See Note 13F, "Commitments and Contingencies - Eversource and NSTAR Electric Boston Harbor Civil Action," to the financial statements for further information on the HEEC distribution cable.

INVESTMENTS IN UNCONSOLIDATED A

INVESTMENTS IN UNCONSOLIDATED AFFILIATES	12 Months Ended
INVESTMENTS IN UNCONSOLIDATED AFFILIATES	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
INVESTMENTS IN UNCONSOLIDATED AFFILIATES	INVESTMENTS IN UNCONSOLIDATED AFFILIATES Investments in entities that are not consolidated are included in long-term assets on the balance sheets and earnings impacts from these equity investments are included in Other Income, Net on the statements of income. Eversource's investments included the following: Investment Balance as of December 31, (Millions of Dollars) Ownership Interest 2019 2018 Offshore Wind Business - North East Offshore and Bay State Wind 50 % $ 649.3 $ 234.3 Natural Gas Pipeline - Algonquin Gas Transmission, LLC 15 % 127.8 155.0 Renewable Energy Investment Fund 90 % 72.4 54.1 Other various 22.1 20.9 Total Investments in Unconsolidated Affiliates $ 871.6 $ 464.3 For the years ended December 31, 2019, 2018 and 2017, Eversource had equity in earnings, net of impairment, of unconsolidated affiliates of $42.2 million , $3.8 million , and $27.4 million , respectively. Eversource received dividends from its equity method investees of $48.9 million , $22.3 million and $20.0 million , respectively, for the years ended December 31, 2019, 2018 and 2017. Investments in affiliates where Eversource has the ability to exercise significant influence, but not control, over an investee are initially recognized as an equity method investment at cost. Any differences between the cost of an investment and the amount of underlying equity in net assets of an investee are considered basis differences, and are determined based upon the estimated fair values of the investee's identifiable assets and liabilities. The carrying amount of Eversource’s offshore wind investments exceeded its share of underlying equity in net assets by $240.3 million and $7.2 million , respectively, as of December 31, 2019 and 2018. As of December 31, 2019, these basis differences are primarily comprised of $168.3 million of equity method goodwill that is not being amortized, intangible assets for PPAs, which will be amortized over the term of the PPAs, and capitalized interest. Offshore Wind Business: Eversource's offshore wind business includes ownership interests in North East Offshore and Bay State Wind, which together hold PPAs and contracts for the Revolution Wind, South Fork Wind and Sunrise Wind projects, as well as offshore leases through BOEM. Eversource's offshore wind projects are being developed and constructed through a joint and equal partnership with Ørsted. On February 8, 2019, Eversource and Ørsted entered into an equal partnership to acquire key offshore wind assets in the Northeast. Eversource has a 50 percent ownership interest in North East Offshore, which holds the Revolution Wind and South Fork Wind projects, as well as a 257 square-mile lease off the coasts of Massachusetts and Rhode Island. Eversource also has a 50 percent ownership interest in Bay State Wind, which holds the Sunrise Wind project. Bay State Wind's separate 300 -square-mile ocean lease is located approximately 25 miles south of the coast of Massachusetts adjacent to the North East Offshore area. NSTAR Electric: As of December 31, 2019 and 2018 , NSTAR Electric's investments included a 14.5 percent ownership interest in two companies that transmit hydro-electricity imported from the Hydro-Quebec system in Canada of $8.2 million and $7.6 million , respectively. Impairment of Equity Method Investments: Equity method investments are assessed for impairment when conditions exist that indicate that the fair value of the investment is less than book value. If the decline in value is considered to be other-than-temporary, the investment is written down to its estimated fair value, which establishes a new cost basis in the investment. Impairment evaluations involve a significant degree of judgment and estimation, including identifying circumstances that indicate an impairment may exist and developing undiscounted future cash flows. During the year ended December 31, 2018, Eversource recorded an other-than-temporary impairment of $32.9 million

SHORT-TERM DEBT

SHORT-TERM DEBT	12 Months Ended
SHORT-TERM DEBT	Dec. 31, 2019
Debt Disclosure [Abstract]
SHORT-TERM DEBT	SHORT-TERM DEBT Short-Term Debt Borrowing Limits: The amount of short-term borrowings that may be incurred by CL&P and NSTAR Electric is subject to periodic approval by the FERC. Because the NHPUC has jurisdiction over PSNH's short-term debt, PSNH is not currently required to obtain FERC approval for its short-term borrowings. On October 25, 2019, the FERC granted authorization that allows CL&P to issue total short-term borrowings in an aggregate principal amount not to exceed $600 million outstanding at any one time, through December 31, 2021. On December 18, 2019, the FERC granted authorization that allows NSTAR Electric to issue total short-term borrowings in an aggregate principal amount not to exceed $655 million outstanding at any one time, through December 31, 2021. PSNH is authorized by regulation of the NHPUC to incur short-term borrowings up to 10 percent of net fixed plant plus an additional $60 million until further ordered by the NHPUC. As of December 31, 2019 , PSNH's short-term debt authorization under the 10 percent of net fixed plant test plus $60 million totaled approximately $354 million . CL&P's certificate of incorporation contains preferred stock provisions restricting the amount of unsecured debt that CL&P may incur, including limiting unsecured indebtedness with a maturity of less than 10 years to 10 percent of total capitalization. As of December 31, 2019 , CL&P had $738.1 million of unsecured debt capacity available under this authorization. Yankee Gas and NSTAR Gas are not required to obtain approval from any state or federal authority to incur short-term debt. Commercial Paper Programs and Credit Agreements : Eversource parent has a $1.45 billion commercial paper program allowing Eversource parent to issue commercial paper as a form of short-term debt. Eversource parent, CL&P, PSNH, NSTAR Gas, Yankee Gas and Aquarion Water Company of Connecticut are also parties to a five -year $1.45 billion revolving credit facility. Effective December 9, 2019, the revolving credit facility's termination date was extended for one additional year to December 6, 2024. The revolving credit facility serves to backstop Eversource parent's $1.45 billion commercial paper program. NSTAR Electric has a $650 million commercial paper program allowing NSTAR Electric to issue commercial paper as a form of short-term debt. NSTAR Electric is also a party to a five -year $650 million revolving credit facility. Effective December 9, 2019, the revolving credit facility's termination date was extended for one additional year to December 6, 2024. The revolving credit facility serves to backstop NSTAR Electric's $650 million commercial paper program. The amount of borrowings outstanding and available under the commercial paper programs were as follows: Borrowings Outstanding as of December 31, Available Borrowing Capacity as of December 31, Weighted-Average Interest Rate as of December 31, (Millions of Dollars) 2019 2018 2019 2018 2019 2018 Eversource Parent Commercial Paper Program $ 1,224.9 $ 631.5 $ 225.1 $ 818.5 1.98 % 2.77 % NSTAR Electric Commercial Paper Program 10.5 278.5 639.5 371.5 1.63 % 2.50 % There were no borrowings outstanding on either the Eversource parent or NSTAR Electric revolving credit facilities as of December 31, 2019 or 2018 . Amounts outstanding under the commercial paper programs and revolving credit facilities are included in Notes Payable and classified in current liabilities on the Eversource and NSTAR Electric balance sheets as all borrowings are outstanding for no more than 364 days at one time. As a result of the Eversource parent long-term debt issuance on January 10, 2020, the net proceeds of which were used to repay short-term borrowings outstanding under its commercial paper program, $346.3 million of commercial paper borrowings under the Eversource parent commercial paper program were classified as Long-Term Debt as of December 31, 2019. Under the credit facilities described above, Eversource and its subsidiaries must comply with certain financial and non-financial covenants, including a consolidated debt to total capitalization ratio. As of December 31, 2019 and 2018 , Eversource and its subsidiaries were in compliance with these covenants. If Eversource or its subsidiaries were not in compliance with these covenants, an event of default would occur requiring all outstanding borrowings by such borrower to be repaid, and additional borrowings by such borrower would not be permitted under its respective credit facility. The Company expects the future operating cash flows of Eversource, CL&P, NSTAR Electric and PSNH, along with existing borrowing availability and access to both debt and equity markets, will be sufficient to meet any working capital and future operating requirements, and capital investment forecasted opportunities. Intercompany Borrowings: Eversource parent uses its available capital resources to provide loans to its subsidiaries to assist in meeting their short-term borrowing needs. Eversource parent records intercompany interest income from its loans to subsidiaries, which is eliminated in consolidation. Intercompany loans from Eversource parent to its subsidiaries are eliminated in consolidation on Eversource's balance sheets. As of December 31, 2019 , there were intercompany loans from Eversource parent to CL&P of $ 63.8 million , to PSNH of $27.0 million , and to a subsidiary of NSTAR Electric of $30.3 million . As of December 31, 2018 , there were intercompany loans from Eversource parent to PSNH of $ 57.0 million

LONG-TERM DEBT

LONG-TERM DEBT	12 Months Ended
LONG-TERM DEBT	Dec. 31, 2019
Debt Disclosure [Abstract]
LONG-TERM DEBT	LONG-TERM DEBT Details of long-term debt outstanding are as follows: CL&P (Millions of Dollars) As of December 31, 2019 2018 First Mortgage Bonds: 7.875% 1994 Series D due 2024 $ 139.8 $ 139.8 5.750% 2004 Series B due 2034 130.0 130.0 5.625% 2005 Series B due 2035 100.0 100.0 6.350% 2006 Series A due 2036 250.0 250.0 5.750% 2007 Series B due 2037 150.0 150.0 6.375% 2007 Series D due 2037 100.0 100.0 5.500% 2009 Series A due 2019 — 250.0 2.500% 2013 Series A due 2023 400.0 400.0 4.300% 2014 Series A due 2044 475.0 475.0 4.150% 2015 Series A due 2045 350.0 350.0 3.200% 2017 Series A due 2027 500.0 300.0 4.000% 2018 Series A due 2048 800.0 500.0 Total First Mortgage Bonds 3,394.8 3,144.8 Pollution Control Revenue Bonds: 4.375% Fixed Rate Tax Exempt due 2028 120.5 120.5 Less Amounts due Within One Year — (250.0 ) Unamortized Premiums and Discounts, Net 27.8 10.2 Unamortized Debt Issuance Costs (25.0 ) (21.5 ) CL&P Long-Term Debt $ 3,518.1 $ 3,004.0 NSTAR Electric (Millions of Dollars) As of December 31, 2019 2018 Debentures: 5.750% due 2036 $ 200.0 $ 200.0 5.500% due 2040 300.0 300.0 2.375% due 2022 400.0 400.0 4.400% due 2044 300.0 300.0 3.250% due 2025 250.0 250.0 2.700% due 2026 250.0 250.0 3.200% due 2027 700.0 700.0 3.250% due 2029 400.0 — Total Debentures 2,800.0 2,400.0 Notes: 5.900% Senior Notes Series B due 2034 50.0 50.0 6.700% Senior Notes Series D due 2037 40.0 40.0 5.100% Senior Notes Series E due 2020 95.0 95.0 3.500% Senior Notes Series F due 2021 250.0 250.0 3.880% Senior Notes Series G due 2023 80.0 80.0 2.750% Senior Notes Series H due 2026 50.0 50.0 Total Notes 565.0 565.0 Less Amounts due Within One Year (95.0 ) — Unamortized Premiums and Discounts, Net (4.1 ) (2.5 ) Unamortized Debt Issuance Costs (18.8 ) (17.7 ) NSTAR Electric Long-Term Debt $ 3,247.1 $ 2,944.8 PSNH (Millions of Dollars) As of December 31, 2019 2018 First Mortgage Bonds: 5.600% Series M due 2035 $ 50.0 $ 50.0 4.500% Series P due 2019 — 150.0 4.050% Series Q due 2021 122.0 122.0 3.200% Series R due 2021 160.0 160.0 3.500% Series S due 2023 325.0 325.0 3.600% Series T due 2049 300.0 — Total First Mortgage Bonds 957.0 807.0 Less Amounts due Within One Year — (150.0 ) Unamortized Premiums and Discounts, Net (0.7 ) — Unamortized Debt Issuance Costs (4.7 ) (1.8 ) PSNH Long-Term Debt $ 951.6 $ 655.2 OTHER (Millions of Dollars) As of December 31, 2019 2018 Yankee Gas - First Mortgage Bonds: 2.230% - 8.480% due 2020 - 2049 $ 620.0 $ 470.0 NSTAR Gas - First Mortgage Bonds: 3.740% - 9.950% due 2020 - 2049 460.0 385.0 Aquarion - Senior Note 4.000% due 2024 360.0 360.0 Aquarion - Unsecured Notes 0% - 6.430% due 2021 - 2049 335.3 289.5 Aquarion - Secured Debt 4.100% - 9.640% due 2021 - 2035 68.8 70.7 Eversource Parent - Debentures 4.500% due 2019 — 350.0 Eversource Parent - Senior Notes 2.500% - 4.250% due 2021 - 2029 4,000.0 4,000.0 Pre-1983 Spent Nuclear Fuel Obligation (CYAPC) 11.6 39.5 Fair Value Adjustment (1) 109.1 144.7 Less Fair Value Adjustment - Current Portion (1) (31.3 ) (36.2 ) Less Amounts due in One Year (201.1 ) (401.1 ) Commercial Paper Classified as Long-Term Debt (See Note 8, Short-Term Debt) 346.3 — Unamortized Premiums and Discounts, Net (4.1 ) (4.2 ) Unamortized Debt Issuance Costs (20.6 ) (23.2 ) Total Other Long-Term Debt $ 6,054.0 $ 5,644.7 Total Eversource Long-Term Debt $ 13,770.8 $ 12,248.7 (1) The fair value adjustment amount is the purchase price adjustments, net of amortization, required to record long-term debt at fair value on the dates of the 2012 merger with NSTAR and the 2017 acquisition of Aquarion. Long-Term Debt Issuances and Repayments: The following table summarizes long-term debt issuances and repayments: (Millions of Dollars) Issue Date Issuance/(Repayment) Maturity Date Use of Proceeds for Issuance/ CL&P: 4.00% 2018 Series A First Mortgage Bonds (1) April 2019 $ 300.0 April 2048 Paid short-term borrowings that were used to pay long-term debt that matured on February 1, 2019 and fund capital expenditures and working capital 3.20% 2017 Series A First Mortgage Bonds (2) September 2019 200.0 March 2027 Paid short-term borrowings and fund capital expenditures and working capital 5.50% 2009 Series A First Mortgage Bonds February 2009 (250.0 ) February 2019 Paid at maturity on February 1, 2019 NSTAR Electric: 3.25% 2019 Debentures May 2019 400.0 May 2029 Paid short-term borrowings that were used to fund investments in eligible green expenditures PSNH: 3.60% 2019 Series T First Mortgage Bonds June 2019 300.0 July 2049 Paid long-term debt that matured in December 2019, paid short-term borrowings and fund capital expenditures and working capital 4.50% 2009 Series P First Mortgage Bonds December 2009 (150.0 ) December 2019 Paid at maturity on December 1, 2019 Other: Eversource Parent 4.50% Debentures November 2009 (350.0 ) November 2019 Paid at maturity on November 15, 2019 Eversource Parent 3.45% Series P Senior Notes January 2020 350.0 January 2050 Paid short-term borrowings NSTAR Gas 3.74% Series Q First Mortgage Bonds July 2019 75.0 August 2049 Paid short-term borrowings and fund capital expenditures and working capital Yankee Gas 2.23% Series P First Mortgage Bonds September 2019 100.0 October 2024 Paid short-term borrowings and for general corporate purposes Yankee Gas 3.30% Series Q First Mortgage Bonds September 2019 100.0 October 2049 Paid short-term borrowings and for general corporate purposes Yankee Gas 5.26% Series H First Mortgage Bonds November 2004 (50.0 ) November 2019 Paid at maturity on November 1, 2019 Aquarion 3.54% Senior Notes December 2019 45.0 December 2049 Paid short-term borrowings (1) These bonds are part of the same series issued by CL&P in March 2018. The aggregate outstanding principal amount of these bonds is now $800 million . (2) These bonds are part of the same series issued by CL&P in March 2017. The aggregate outstanding principal amount of these bonds is now $500 million . Long-Term Debt Issuance Authorizations: On February 27, 2019, the DPU approved NSTAR Electric's request for authorization to issue up to $800 million in long-term debt through December 31, 2020. On April 26, 2019, the NHPUC approved PSNH's request for authorization to issue up to $300 million in long-term debt through December 31, 2019. On August 14, 2019, PURA approved CL&P's request for authorization to issue up to $675 million in long-term debt through December 31, 2022. On December 11, 2019, PURA approved Aquarion Water Company of Connecticut's request for authorization to issue up to $45 million of long-term debt. On January 27, 2020, the DPU approved NSTAR Gas' request for authorization to issue up to $270 million in long-term debt through December 31, 2021. Long-Term Debt Provisions: The utility plant of CL&P, PSNH, Yankee Gas, NSTAR Gas and a portion of Aquarion is subject to the lien of each company's respective first mortgage bond indenture. The Eversource parent, NSTAR Electric and a portion of Aquarion debt is unsecured. Additionally, the long-term debt agreements provide that Eversource and certain of its subsidiaries must comply with certain covenants as are customarily included in such agreements, including equity requirements for NSTAR Electric, NSTAR Gas and Aquarion. Under the equity requirements, NSTAR Electric's and Aquarion's senior notes must maintain a certain consolidated indebtedness to capitalization ratio as of the end of any fiscal quarter and NSTAR Gas' outstanding long-term debt must not exceed equity. CL&P's obligation to repay the Pollution Control Revenue Bonds (PCRBs) is secured by first mortgage bonds. The first mortgage bonds contain similar terms and provisions as the applicable series of PCRBs. If CL&P fails to meet its obligations under the first mortgage bonds, then the holder of the first mortgage bonds (the issuer of the PCRBs) would have rights under the first mortgage bonds. CL&P's tax-exempt PCRBs will be subject to redemption at par on or after September 1, 2021. Certain secured and unsecured long-term debt securities are callable at redemption price or are subject to make-whole provisions. Eversource, NSTAR Electric, Yankee Gas and Aquarion have certain long-term debt agreements that contain cross-default provisions. No other debt issuances contain cross-default provisions as of December 31, 2019 . CYAPC's Pre-1983 Spent Nuclear Fuel Obligation: Under the Nuclear Waste Policy Act of 1982, the DOE is responsible for the selection and development of repositories for, and the disposal of, spent nuclear fuel and high-level radioactive waste. CYAPC is obligated to pay the DOE for the costs to dispose of spent nuclear fuel and high-level radioactive waste generated prior to April 7, 1983 (pre-1983 Spent Nuclear Fuel) and recorded an accrual for the full liability thereof to the DOE. This liability accrues interest costs at the 3-month Treasury bill yield rate. For nuclear fuel used to generate electricity prior to April 7, 1983, payment may be made any time prior to the first delivery of spent fuel to the DOE. Fees for disposal of nuclear fuel burned on or after April 7, 1983 were billed to member companies and paid to the DOE. As of December 31, 2019 and 2018 , as a result of consolidating CYAPC, Eversource has consolidated $11.6 million and $39.5 million , respectively, in pre-1983 spent nuclear fuel obligations to the DOE. In December 2019 and 2018, CYAPC paid $29 million and $145 million , respectively, to the DOE to partially settle this obligation. The obligation includes accumulated interest costs of $8.6 million and $29.0 million as of December 31, 2019 and 2018 , respectively. CYAPC maintains a trust to fund amounts due to the DOE for the disposal of pre-1983 spent nuclear fuel. For further information, see Note 5, "Marketable Securities," to the financial statements. Long-Term Debt Maturities: Long-term debt maturities on debt outstanding for the years 2020 through 2024 and thereafter are shown below. These amounts exclude PSNH rate reduction bonds, CYAPC pre-1983 spent nuclear fuel obligation, net unamortized premiums, discounts and debt issuance costs, and other fair value adjustments as of December 31, 2019 : (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2020 $ 296.1 $ — $ 95.0 $ — 2021 1,033.6 — 250.0 282.0 2022 1,188.9 — 400.0 — 2023 1,665.2 400.0 80.0 325.0 2024 1,049.8 139.8 — — Thereafter 8,447.8 2,975.5 2,540.0 350.0 Total $ 13,681.4 $ 3,515.3 $ 3,365.0 $ 957.0

RATE REDUCTION BONDS AND VARIAB

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES	12 Months Ended
RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES	Dec. 31, 2019
Rate Reduction Bonds and Variable Interest Entity [Abstract]
RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES	RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES Rate Reduction Bonds: On May 8, 2018, PSNH Funding, a wholly-owned subsidiary of PSNH, issued $635.7 million of securitized RRBs in multiple tranches with a weighted average interest rate of 3.66 percent , and final maturity dates ranging from 2026 to 2035. The RRBs are expected to be repaid by February 1, 2033. RRB payments consist of principal and interest and are paid semi-annually, beginning on February 1, 2019. The RRBs were issued pursuant to a finance order issued by the NHPUC on January 30, 2018 to recover remaining costs resulting from the divestiture of PSNH’s generation assets. The proceeds were used by PSNH Funding to purchase PSNH’s stranded cost asset-recovery property, including its vested property right to bill, collect and adjust a non-bypassable stranded cost recovery charge from PSNH’s retail customers. The collections are used to pay principal, interest and other costs in connection with the RRBs. The RRBs are secured by the stranded cost asset-recovery property. Cash collections from the stranded cost recovery charges and funds on deposit in trust accounts are the sole source of funds to satisfy the debt obligation. PSNH is not the owner of the RRBs, and PSNH Funding’s assets and revenues are not available to pay PSNH’s creditors. The RRBs are non-recourse senior secured obligations of PSNH Funding and are not insured or guaranteed by PSNH or Eversource Energy. PSNH Funding was formed solely to issue RRBs to finance PSNH’s unrecovered remaining costs associated with the divestiture of its generation assets. PSNH Funding is considered a VIE primarily because the equity capitalization is insufficient to support its operations. PSNH has the power to direct the significant activities of the VIE and is most closely associated with the VIE as compared to other interest holders. Therefore, PSNH is considered the primary beneficiary and consolidates PSNH Funding in its consolidated financial statements. The following tables summarize the impact of PSNH Funding on PSNH's balance sheets and income statements: (Millions of Dollars) Balance Sheet: As of December 31, 2019 As of December 31, 2018 Restricted Cash - Current Portion (included in Current Assets) $ 32.5 $ 47.5 Restricted Cash - Long-Term Portion (included in Other Long-Term Assets) 3.2 3.2 Securitized Stranded Cost (included in Regulatory Assets) 565.3 608.4 Other Regulatory Liabilities (included in Regulatory Liabilities) 5.6 5.8 Accrued Interest (included in Other Current Liabilities) 8.6 14.4 Rate Reduction Bonds - Current Portion 43.2 52.3 Rate Reduction Bonds - Long-Term Portion 540.1 583.3 (Millions of Dollars) Income Statement: For the Year Ended December 31, 2019 For the Year Ended December 31, 2018 Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net) $ 43.0 $ 27.3 Interest Expense on RRB Principal (included in Interest Expense) 21.1 14.4 Variable Interest Entities - Other: The Company's variable interests outside of the consolidated group include contracts that are required by regulation and provide for regulatory recovery of contract costs and benefits through customer rates. Eversource, CL&P and NSTAR Electric hold variable interests in VIEs through agreements with certain entities that own single renewable energy or peaking generation power plants, with other independent power producers and with transmission businesses. Eversource, CL&P and NSTAR Electric do not control the activities that are economically significant to these VIEs or provide financial or other support to these VIEs. Therefore, Eversource, CL&P and NSTAR Electric do not consolidate these VIEs.

EMPLOYEE BENEFITS

EMPLOYEE BENEFITS	12 Months Ended
EMPLOYEE BENEFITS	Dec. 31, 2019
Postemployment Benefits [Abstract]
EMPLOYEE BENEFITS	EMPLOYEE BENEFITS A. Pension Benefits and Postretirement Benefits Other Than Pension Eversource provides defined benefit retirement plans (Pension Plans) that cover eligible employees and are subject to the provisions of ERISA, as amended by the Pension Protection Act of 2006. Eversource's policy is to annually fund the Pension Plans in an amount at least equal to an amount that will satisfy all federal funding requirements. In addition to the Pension Plans, Eversource maintains non-qualified defined benefit retirement plans (SERP Plans) which provide benefits in excess of Internal Revenue Code limitations to eligible participants consisting of current and retired employees. Eversource also provides defined benefit postretirement plans (PBOP Plans) that provide life insurance and a health reimbursement arrangement created for the purpose of reimbursing retirees and dependents for health insurance premiums and certain medical expenses to eligible employees that meet certain age and service eligibility requirements. The benefits provided under the PBOP Plans are not vested, and the Company has the right to modify any benefit provision subject to applicable laws at that time. Eversource annually funds postretirement costs through tax deductible contributions to external trusts. The Pension, SERP and PBOP Plans cover eligible employees, including, among others, employees of the regulated companies. Because the regulated companies recover retiree benefit costs from customers through rates, regulatory assets are recorded in lieu of recording an adjustment to Accumulated Other Comprehensive Income/(Loss) as an offset to the funded status of the Pension, SERP and PBOP Plans. Regulatory accounting is also applied to the portions of the Eversource Service retiree benefit costs that support the regulated companies, as these costs are also recovered from customers. Adjustments to the Pension, SERP and PBOP Plans' funded status for the unregulated companies are recorded on an after-tax basis to Accumulated Other Comprehensive Income/(Loss). For further information, see Note 2, "Regulatory Accounting," and Note 17, "Accumulated Other Comprehensive Income/(Loss)," to the financial statements. Funded Status: The Pension, SERP and PBOP Plans are accounted for under the multiple-employer approach, with each operating company's balance sheet reflecting its share of the funded status of the plans. Although Eversource maintains marketable securities in a benefit trust, the SERP Plans do not contain any assets. For further information, see Note 5, "Marketable Securities," to the financial statements. The following tables provide information on the plan benefit obligations, fair values of plan assets, and funded status: Pension and SERP As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Change in Benefit Obligation: Benefit Obligation as of Beginning of Year $ (5,520.0 ) $ (1,160.4 ) $ (1,236.5 ) $ (610.7 ) $ (5,936.5 ) $ (1,275.2 ) $ (1,351.0 ) $ (642.2 ) Service Cost (67.7 ) (18.0 ) (14.6 ) (7.1 ) (84.8 ) (21.4 ) (17.4 ) (11.2 ) Interest Cost (219.0 ) (45.7 ) (49.0 ) (24.0 ) (196.4 ) (41.8 ) (43.5 ) (22.0 ) Actuarial Gain/(Loss) (815.3 ) (176.6 ) (181.0 ) (84.5 ) 414.9 106.1 98.6 39.2 Benefits Paid - Pension 273.0 60.2 67.1 30.3 261.8 59.6 66.9 26.2 Benefits Paid - Lump Sum 20.0 — 12.9 — 14.2 — 7.1 — Benefits Paid - SERP 7.3 0.3 0.1 0.4 6.8 0.3 0.3 0.2 Employee Transfers — 8.9 3.7 3.0 — 12.0 2.5 (0.9 ) Benefit Obligation as of End of Year $ (6,321.7 ) $ (1,331.3 ) $ (1,397.3 ) $ (692.6 ) $ (5,520.0 ) $ (1,160.4 ) $ (1,236.5 ) $ (610.7 ) Change in Pension Plan Assets: Fair Value of Pension Plan Assets as of Beginning of Year $ 4,573.9 $ 918.4 $ 1,222.1 $ 506.6 $ 4,739.5 $ 963.0 $ 1,260.8 $ 539.5 Employer Contributions 112.5 24.0 0.4 15.4 185.6 41.2 56.5 — Actual Return on Pension Plan Assets 575.2 112.9 150.0 62.9 (75.2 ) (14.2 ) (18.7 ) (7.6 ) Benefits Paid - Pension (273.0 ) (60.2 ) (67.1 ) (30.3 ) (261.8 ) (59.6 ) (66.9 ) (26.2 ) Benefits Paid - Lump Sum (20.0 ) — (12.9 ) — (14.2 ) — (7.1 ) — Employee Transfers — (8.9 ) (3.7 ) (3.0 ) — (12.0 ) (2.5 ) 0.9 Fair Value of Pension Plan Assets as of End of Year $ 4,968.6 $ 986.2 $ 1,288.8 $ 551.6 $ 4,573.9 $ 918.4 $ 1,222.1 $ 506.6 Funded Status as of December 31st $ (1,353.1 ) $ (345.1 ) $ (108.5 ) $ (141.0 ) $ (946.1 ) $ (242.0 ) $ (14.4 ) $ (104.1 ) As of December 31, 2019 , there was a decrease in the discount rate used to calculate the pension funded status, which resulted in an increase to Eversource's pension liability of $813.1 million , which was partially offset by changes in actual plan experience and changes in other assumptions. As of December 31, 2018, there was an increase in the discount rate used to calculate the pension funded status, which resulted in a decrease to Eversource's pension liability of approximately $465 million , which was partially offset by changes in actual plan experience and changes in other assumptions. The pension and SERP Plans' funded status includes the current portion of the SERP liability totaling $8.7 million and $8.9 million as of December 31, 2019 and 2018 , respectively, which is included in Other Current Liabilities on the balance sheets. As of December 31, 2019 and 2018 , the accumulated benefit obligation for the Pension and SERP Plans is as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 5,963.4 $ 1,205.4 $ 1,340.8 $ 646.7 2018 5,070.8 1,031.0 1,144.7 543.1 PBOP As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Change in Benefit Obligation: Benefit Obligation as of Beginning of Year $ (841.5 ) $ (161.7 ) $ (246.3 ) $ (91.9 ) $ (948.6 ) $ (178.4 ) $ (278.6 ) $ (101.1 ) Service Cost (7.8 ) (1.4 ) (1.7 ) (0.7 ) (10.0 ) (1.9 ) (2.0 ) (1.1 ) Interest Cost (32.7 ) (6.3 ) (9.5 ) (3.4 ) (30.7 ) (5.8 ) (8.7 ) (3.4 ) Actuarial Gain/(Loss) (67.0 ) (13.4 ) (15.2 ) (3.1 ) 102.5 14.4 28.4 8.6 Benefits Paid 50.0 10.8 15.4 5.6 45.3 10.1 14.5 4.9 Employee Transfers — (0.7 ) (1.0 ) 0.5 — (0.1 ) 0.1 0.2 Benefit Obligation as of End of Year $ (899.0 ) $ (172.7 ) $ (258.3 ) $ (93.0 ) $ (841.5 ) $ (161.7 ) $ (246.3 ) $ (91.9 ) Change in Plan Assets: Fair Value of Plan Assets as of Beginning of Year $ 849.6 $ 120.6 $ 379.1 $ 71.2 $ 922.2 $ 135.9 $ 405.5 $ 79.0 Actual Return on Plan Assets 127.0 17.1 57.0 10.0 (36.6 ) (5.2 ) (17.4 ) (2.9 ) Employer Contributions 9.3 — 6.0 — 9.3 — 5.2 — Benefits Paid (50.0 ) (10.8 ) (15.4 ) (5.6 ) (45.3 ) (10.1 ) (14.5 ) (4.9 ) Employee Transfers — (0.6 ) (2.3 ) 0.4 — — 0.3 — Fair Value of Plan Assets as of End of Year $ 935.9 $ 126.3 $ 424.4 $ 76.0 $ 849.6 $ 120.6 $ 379.1 $ 71.2 Funded Status as of December 31st $ 36.9 $ (46.4 ) $ 166.1 $ (17.0 ) $ 8.1 $ (41.1 ) $ 132.8 $ (20.7 ) The Eversource PBOP funded status includes prepaid assets of $62.7 million and $33.4 million recorded in Other Long-Term Assets and liabilities of $25.8 million and $25.3 million included in Accrued Pension, SERP and PBOP on the balance sheets as of December 31, 2019 and 2018 , respectively. As of December 31, 2019 , there was a decrease in the discount rate used to calculate the PBOP funded status, which resulted in an increase to the Eversource PBOP liability of $88.6 million . As of December 31, 2018, there was an increase in the discount rate used to calculate the funded status, which resulted in a decrease to the Eversource PBOP liability of approximately $88 million . The following actuarial assumptions were used in calculating the Pension, SERP and PBOP Plans' year end funded status: Pension and SERP PBOP As of December 31, As of December 31, 2019 2018 2019 2018 Discount Rate 3.04% — 3.35% 4.22% — 4.45% 3.26% — 3.28% 4.38% — 4.41% Compensation/Progression Rate 3.50% — 4.00% 3.50% — 4.00% N/A For the Eversource Service PBOP Plan, the health care cost trend rate is not applicable. For the Aquarion PBOP Plan, the health care trend rate is a range of 3.5 percent to 6.5 percent , with an ultimate rate of 3.5 percent to 5 percent in 2019 and 2023, for post-65 and pre-65 retirees, respectively. Expense: Eversource charges net periodic benefit expense/(income) for the Pension, SERP and PBOP Plans to its subsidiaries based on the actual participant demographic data for each subsidiary's participants. The actual investment return in the trust is allocated to each of the subsidiaries annually in proportion to the investment return expected to be earned during the year. The Company utilizes the spot rate methodology to estimate the discount rate for the service and interest cost components of benefit expense, which provides a more precise measurement by matching projected cash flows to the corresponding spot rates on the yield curve. The components of net periodic benefit expense/(income) for the Pension, SERP and PBOP Plans, prior to amounts capitalized as Property, Plant and Equipment or deferred as regulatory assets for future recovery, are shown below. The service cost component of net periodic benefit expense/(income), less the capitalized portion, is included in Operations and Maintenance expense on the statements of income. The remaining components of net periodic benefit expense/(income), less the deferred portion, are included in Other Income, Net on the statements of income. Pension, SERP and PBOP expense reflected in the statements of cash flows for CL&P, NSTAR Electric and PSNH does not include the intercompany allocations or the corresponding capitalized and deferred portion, as these amounts are cash settled on a short-term basis. Pension and SERP PBOP For the Year Ended December 31, 2019 For the Year Ended December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 67.7 $ 18.0 $ 14.6 $ 7.1 $ 7.8 $ 1.4 $ 1.7 $ 0.7 Interest Cost 219.0 45.7 49.0 24.0 32.7 6.3 9.5 3.4 Expected Return on Plan Assets (367.1 ) (73.2 ) (97.1 ) (40.7 ) (66.8 ) (9.2 ) (30.2 ) (5.4 ) Actuarial Loss 143.2 26.9 44.7 10.6 8.3 1.3 3.3 0.3 Prior Service Cost/(Credit) 0.9 — 0.3 — (23.5 ) 1.1 (16.9 ) 0.4 Total Net Periodic Benefit Expense/(Income) $ 63.7 $ 17.4 $ 11.5 $ 1.0 $ (41.5 ) $ 0.9 $ (32.6 ) $ (0.6 ) Intercompany Allocations N/A $ 8.5 $ 8.0 $ 2.3 N/A $ (0.9 ) $ (1.2 ) $ (0.4 ) Pension and SERP PBOP For the Year Ended December 31, 2018 For the Year Ended December 31, 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 84.8 $ 21.4 $ 17.4 $ 11.2 $ 10.0 $ 1.9 $ 2.0 $ 1.1 Interest Cost 196.4 41.8 43.5 22.0 30.7 5.8 8.7 3.4 Expected Return on Plan Assets (391.6 ) (79.1 ) (104.9 ) (43.6 ) (72.4 ) (10.4 ) (32.5 ) (6.0 ) Actuarial Loss 145.7 29.1 41.1 11.6 10.3 1.6 2.3 0.7 Prior Service Cost/(Credit) 4.3 1.1 0.2 0.4 (23.6 ) 1.1 (16.9 ) 0.5 Total Net Periodic Benefit Expense/(Income) $ 39.6 $ 14.3 $ (2.7 ) $ 1.6 $ (45.0 ) $ — $ (36.4 ) $ (0.3 ) Intercompany Allocations N/A $ 6.1 $ 6.5 $ 1.9 N/A $ (1.0 ) $ (1.3 ) $ (0.4 ) Pension and SERP PBOP For the Year Ended December 31, 2017 For the Year Ended December 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 71.3 $ 18.5 $ 15.5 $ 9.7 $ 9.5 $ 1.9 $ 1.7 $ 1.3 Interest Cost 188.0 41.6 42.7 21.2 27.1 5.3 8.7 3.0 Expected Return on Plan Assets (334.1 ) (71.7 ) (87.6 ) (40.0 ) (63.7 ) (9.7 ) (28.6 ) (5.5 ) Actuarial Loss 135.2 27.7 41.1 11.6 9.1 1.0 3.4 0.6 Prior Service Cost/(Credit) 4.5 1.5 0.6 0.5 (21.6 ) 1.1 (17.0 ) 0.6 Total Net Periodic Benefit Expense/(Income) $ 64.9 $ 17.6 $ 12.3 $ 3.0 $ (39.6 ) $ (0.4 ) $ (31.8 ) $ — Intercompany Allocations N/A $ 9.8 $ 9.1 $ 3.3 N/A $ (0.7 ) $ (1.1 ) $ (0.5 ) The following actuarial assumptions were used to calculate Pension, SERP and PBOP expense amounts: Pension and SERP PBOP For the Years Ended December 31, For the Years Ended December 31, 2019 2018 2017 2019 2018 2017 Discount Rate 2.63% — 3.55% 3.85% — 4.62% 3.20% — 3.90% 3.85% — 4.65% 3.28% — 3.94% 3.48% — 4.64% Expected Long-Term Rate of Return 8.25% 8.25% 8.25% 8.25% 8.25% 8.25% Compensation/Progression Rate 3.50% — 4.00% 3.50% — 4.00% 3.50% N/A N/A N/A For the Aquarion Pension and PBOP Plans, the expected long-term rate of return was 7 percent for the years ended December 31, 2019 and 2018. For the Aquarion PBOP Plan, the health care trend rate was a range of 3.5 percent to 6.75 percent for the year ended December 31, 2019 , and 7 percent for the year ended December 31, 2018. The following is a summary of the changes in plan assets and benefit obligations recognized in Regulatory Assets and Other Comprehensive Income (OCI) as well as amounts in Regulatory Assets and OCI that were reclassified as net periodic benefit expense during the years presented: Pension and SERP PBOP Regulatory Assets OCI Regulatory Assets OCI For the Years Ended December 31, For the Years Ended December 31, (Millions of Dollars) 2019 2018 2019 2018 2019 2018 2019 2018 Actuarial Losses/(Gains) Arising During the Year $ 591.6 $ 48.6 $ 15.4 $ 0.7 $ 4.6 $ 6.4 $ 2.3 $ (1.2 ) Actuarial Losses Reclassified as Net Periodic Benefit Expense (137.8 ) (140.1 ) (5.4 ) (5.6 ) (8.0 ) (9.9 ) (0.3 ) (0.4 ) Actuarial Losses Securitized as Stranded Costs (1) — (36.7 ) — — — (0.8 ) — — Prior Service Cost Arising During the Year — — — — — 1.3 — — Prior Service (Cost)/Credit Reclassified as Net Periodic Benefit (Expense)/Income (0.7 ) (3.9 ) (0.2 ) (0.4 ) 25.1 23.6 (1.6 ) — Prior Service Cost Securitized as Stranded Costs (1) — (0.1 ) — — — (1.3 ) — — (1) These amounts were reclassified to securitized regulatory assets in connection with the divestiture of PSNH's generation business. For further information see Note 2, "Regulatory Accounting" to the financial statements. The following is a summary of the remaining Regulatory Assets and Accumulated Other Comprehensive Income amounts that have not been recognized as components of net periodic benefit expense as of December 31, 2019 and 2018 , as well as the amounts that are expected to be recognized as components in 2020 : Regulatory Assets as of December 31, Expected 2020 Expense/(Income) AOCI as of December 31, Expected 2020 Expense (Millions of Dollars) 2019 2018 2019 2018 Pension and SERP Actuarial Loss $ 2,261.4 $ 1,807.6 $ 190.3 $ 90.8 $ 80.8 $ 7.2 Prior Service Cost 5.6 6.3 0.9 0.9 1.1 0.2 PBOP Actuarial Loss $ 203.9 $ 207.3 $ 8.3 $ 7.0 $ 5.0 $ 0.2 Prior Service (Credit)/Cost (172.5 ) (197.6 ) (21.4 ) 1.0 2.6 0.2 The difference between the actual return and calculated expected return on plan assets for the Pension and PBOP Plans is reflected as a component of unamortized actuarial gains or losses, which are recorded in Regulatory Assets or Accumulated Other Comprehensive Income/(Loss). Unamortized actuarial gains or losses are amortized as a component of pension and PBOP expense over the estimated average future employee service period. Estimated Future Benefit Payments: The following benefit payments, which reflect expected future service, are expected to be paid by the Pension, SERP and PBOP Plans: (Millions of Dollars) 2020 2021 2022 2023 2024 2025 - 2029 Pension and SERP $ 320.1 $ 328.7 $ 337.5 $ 346.5 $ 352.4 $ 1,813.1 PBOP 58.1 57.9 57.3 56.8 56.2 264.7 Eversource Contributions: Based on the current status of the Pension Plans and federal pension funding requirements, Eversource currently expects to make contributions of $105.0 million in 2020 , of which $23.2 million and $19.5 million will be contributed by CL&P and PSNH, respectively. The remaining $57.3 million is expected to be contributed by other Eversource subsidiaries, primarily Eversource Service. Eversource currently estimates contributing $2.9 million to the PBOP Plans in 2020 . Fair Value of Pension and PBOP Plan Assets: Pension and PBOP funds are held in external trusts. Trust assets, including accumulated earnings, must be used exclusively for Pension and PBOP payments. Eversource's investment strategy for its Pension and PBOP Plans is to maximize the long-term rates of return on these plans' assets within an acceptable level of risk. The investment strategy for each asset category includes a diversification of asset types, fund strategies and fund managers and it establishes target asset allocations that are routinely reviewed and periodically rebalanced. PBOP assets are comprised of assets held in the PBOP Plan trust, as well as specific assets within the Pension Plan trust (401(h) assets). The investment policy and strategy of the 401(h) assets is consistent with that of the defined benefit pension plan. Eversource's expected long-term rates of return on Pension and PBOP Plan assets are based on target asset allocation assumptions and related expected long-term rates of return. In developing its expected long-term rate of return assumptions for the Pension and PBOP Plans, Eversource evaluated input from consultants, as well as long-term inflation assumptions and historical returns. Management has assumed long-term rates of return of 8.25 percent for the Eversource Service Pension and PBOP Plan assets and a 7 percent long-term rate of return for the Aquarion Plans to estimate its 2020 Pension and PBOP costs. These long-term rates of return are based on the assumed rates of return for the target asset allocations as follows: As of December 31, 2019 2018 Eversource Pension Plan and Tax-Exempt Assets Within PBOP Plan Eversource Pension Plan and Tax-Exempt Assets Within PBOP Plan Target Asset Allocation Assumed Rate of Return Target Asset Allocation Assumed Rate of Return Equity Securities: United States 15.0 % 8.5 % 15.0 % 8.5 % Global 10.0 % 8.75 % 10.0 % 8.75 % Non-United States 8.0 % 8.5 % 8.0 % 8.5 % Emerging Markets 4.0 % 10.0 % 4.0 % 10.0 % Debt Securities: Fixed Income 13.0 % 4.0 % 13.0 % 4.0 % Public High Yield Fixed Income 4.0 % 6.5 % 4.0 % 6.5 % Private Debt 15.0 % 9.0 % 15.0 % 9.0 % Private Equity 15.0 % 12.0 % 15.0 % 12.0 % Real Assets 16.0 % 7.5 % 16.0 % 7.5 % The taxable assets within the Eversource PBOP Plan have a target asset allocation of 70 percent equity securities and 30 percent fixed income securities. The target asset allocation for the Aquarion Pension Plan is 54 percent equity, 36 percent debt and 10 percent other. The target asset allocation for the Aquarion PBOP Plan is 54 percent equity, 41 percent debt and 5 percent other. The following table presents, by asset category, the Pension and PBOP Plan assets recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Pension Plan Fair Value Measurements as of December 31, (Millions of Dollars) 2019 2018 Asset Category: Level 1 Level 2 Uncategorized Total Level 1 Level 2 Uncategorized Total Equity Securities (1) $ 592.6 $ — $ 1,349.9 $ 1,942.5 $ 443.4 $ — $ 1,377.8 $ 1,821.2 Fixed Income (2) 99.4 303.0 1,222.8 1,625.2 85.5 160.8 1,265.5 1,511.8 Private Equity 16.9 — 971.4 988.3 6.1 — 834.0 840.1 Real Assets (3) 58.7 — 615.0 673.7 62.9 — 569.1 632.0 Total $ 767.6 $ 303.0 $ 4,159.1 $ 5,229.7 $ 597.9 $ 160.8 $ 4,046.4 $ 4,805.1 Less: 401(h) PBOP Assets (4) (261.1 ) (231.2 ) Total Pension Assets $ 4,968.6 $ 4,573.9 PBOP Plan Fair Value Measurements as of December 31, (Millions of Dollars) 2019 2018 Asset Category: Level 1 Level 2 Uncategorized Total Level 1 Level 2 Uncategorized Total Equity Securities (1) $ 158.0 $ — $ 187.0 $ 345.0 $ 91.9 $ — $ 210.5 $ 302.4 Fixed Income (2) 15.8 39.6 148.1 203.5 22.0 40.3 123.0 185.3 Private Equity — — 26.5 26.5 — — 32.7 32.7 Real Assets (3) 51.2 — 48.6 99.8 27.5 — 70.5 98.0 Total $ 225.0 $ 39.6 $ 410.2 $ 674.8 $ 141.4 $ 40.3 $ 436.7 $ 618.4 Add: 401(h) PBOP Assets (4) 261.1 231.2 Total PBOP Assets $ 935.9 $ 849.6 (1) United States, Global, Non-United States and Emerging Markets equity securities that are uncategorized include investments in commingled funds and hedge funds that are overlaid with equity index swaps and futures contracts. (2) Fixed Income investments that are uncategorized include investments in commingled funds, fixed income funds that invest in a variety of opportunistic and fixed income strategies, and hedge funds that are overlaid with fixed income futures. (3) Real assets include real estate funds and hedge funds. (4) The assets of the Pension Plan include a 401(h) account that has been allocated to provide health and welfare postretirement benefits under the PBOP Plan. The Company values assets based on observable inputs when available. Equity securities, exchange traded funds and futures contracts classified as Level 1 in the fair value hierarchy are priced based on the closing price on the primary exchange as of the balance sheet date. Fixed income securities, such as government issued securities and corporate bonds, are included in Level 2 and are valued using pricing models, quoted prices of securities with similar characteristics or discounted cash flows. The pricing models utilize observable inputs such as recent trades for the same or similar instruments, yield curves, discount margins and bond structures. Swaps are valued using pricing models that incorporate interest rates and equity and fixed income index closing prices to determine a net present value of the cash flows. Eversource maintains defined contribution plans on behalf of eligible participants. The Eversource 401k Plan provides for employee and employer contributions up to statutory limits. For eligible employees, the Eversource 401k Plan provides employer matching contributions of either 100 percent up to a maximum of three percent of eligible compensation or 50 percent up to a maximum of eight percent of eligible compensation. The Eversource 401k Plan also contains a K-Vantage feature for the benefit of eligible participants, which provides an additional annual employer contribution based on age and years of service. K-Vantage participants are not eligible to actively participate in the Eversource Pension Plan. The total Eversource 401k Plan employer matching contributions, including the K-Vantage contributions, were as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 41.6 $ 5.5 $ 10.3 $ 3.5 2018 38.4 5.0 9.7 3.3 2017 34.5 4.6 8.5 3.7 Share-based compensation awards are recorded using a fair-value based method at the date of grant. Eversource, CL&P, NSTAR Electric and PSNH record compensation expense related to these awards, as applicable, for shares issued or sold to their respective employees and officers, as well as for the allocation of costs associated with shares issued or sold to Eversource's service company employees and officers that support CL&P, NSTAR Electric and PSNH. Eversource Incentive Plans: Eversource maintains long-term equity-based incentive plans in which Eversource, CL&P, NSTAR Electric and PSNH employees, officers and board members are eligible to participate. The incentive plans authorize Eversource to grant up to 6,700,000 new shares for various types of awards, including RSUs and performance shares, to eligible employees, officers, and board members. As of December 31, 2019 and 2018 , Eversource had 3,302,526 and 3,720,650 common shares, respectively, available for issuance under these plans. Eversource accounts for its various share-based plans as follows: • RSUs - Eversource records compensation expense, net of estimated forfeitures, on a straight-line basis over the requisite service period based upon the fair value of Eversource's common shares at the date of grant. The par value of RSUs is reclassified to Common Stock from Capital Surplus, Paid In as RSUs become issued as common shares. • Performance Shares - Eversource records compensation expense, net of estimated forfeitures, on a straight-line basis over the requisite service period. Performance shares vest based upon the extent to which Company goals are achieved. Vesting of outstanding performance shares is based upon both the Company's EPS growth over the requisite service period and the total shareholder return as compared to the Edison Electric Institute (EEI) Index during the requisite service period. The fair value of performance shares is determined at the date of grant using a lattice model. RSUs: Eversource granted RSUs under the annual long-term incentive programs that are subject to three -year graded vesting schedules for employees, and one -year graded vesting schedules, or immediate vesting, for board members. RSUs are paid in shares, reduced by amounts sufficient to satisfy withholdings for income taxes, subsequent to vesting. A summary of RSU transactions is as follows: RSUs (Units) Weighted Average Grant-Date Fair Value Outstanding as of December 31, 2018 782,365 $ 50.25 Granted 271,144 $ 67.91 Shares Issued (263,219 ) $ 55.34 Forfeited (16,127 ) $ 63.31 Outstanding as of December 31, 2019 774,163 $ 54.43 The weighted average grant-date fair value of RSUs granted for the years ended December 31, 2019 , 2018 and 2017 was $67.91 , $56.69 and $55.97 , respectively. As of December 31, 2019 and 2018 , the number and weighted average grant-date fair value of unvested RSUs was 439,293 and $63.06 per share, and 424,119 and $56.57 per share, respectively. During 2019 , there were 236,359 RSUs at a weighted average grant-date fair value of $57.47 per share that vested during the year and were either paid or deferred. As of December 31, 2019 , 334,870 RSUs were fully vested and deferred and an additional 417,328 are expected to vest. Performance Shares: Eversource granted performance shares under the annual long-term incentive programs that vest based upon the extent to which Company goals are achieved at the end of three-year performance measurement periods. Performance shares are paid in shares, after the performance measurement period. A summary of performance share transactions is as follows: Performance Shares (Units) Weighted Average Grant-Date Fair Value Outstanding as of December 31, 2018 499,564 $ 56.08 Granted 165,022 $ 68.33 Shares Issued (162,959 ) $ 55.69 Forfeited (14,720 ) $ 58.20 Outstanding as of December 31, 2019 486,907 $ 60.30 The weighted average grant-date fair value of performance shares granted for the years ended December 31, 2019 , 2018 and 2017 was $68.33 , $56.77 and $55.70 , respectively. As of December 31, 2019 and 2018 , the number and weighted average grant-date fair value of unvested performance shares was 427,894 and $60.38 per share, and 366,995 and $56.17 per share, respectively. During 2019 , there were 88,664 performance shares at a weighted average grant-date fair value of $58.13 per share that vested during the year and were either paid or deferred. As of December 31, 2019 , 59,013 performance shares were fully vested and deferred. Compensation Expense: The total compensation expense and associated future income tax benefits recognized by Eversource, CL&P, NSTAR Electric and PSNH for share-based compensation awards were as follows: Eversource For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Compensation Expense $ 27.3 $ 21.4 $ 19.7 Future Income Tax Benefit 7.0 5.4 8.0 For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Compensation Expense $ 9.8 $ 9.7 $ 3.3 $ 7.8 $ 7.7 $ 2.9 $ 7.0 $ 7.0 $ 3.2 Future Income Tax Benefit 2.5 2.5 0.8 2.0 1.9 0.7 2.9 2.8 1.3 As of December 31, 2019 , there was $24.4 million of total unrecognized compensation expense related to nonvested share-based awards for Eversource, including $5.3 million for CL&P, $5.3 million for NSTAR Electric and $2.1 million for PSNH. This cost is expected to be recognized ratably over a weighted-average period of 1.75 years for Eversource, 1.79 years for CL&P and NSTAR Electric, and 1.78 years for PSNH. An income tax rate of 25 percent was used to estimate the tax effect on total share-based payments determined under the fair-value based method for all awards. Beginning in 2019, the Company began issuing treasury shares to settle fully vested RSUs and performance shares under the Company's incentive plans. For the years ended December 31, 2019 , 2018 and 2017 , excess tax benefits associated with the distribution of stock compensation awards reduced income tax expense by $1.5 million , $1.5 million , and $2.9 million , respectively, which increased cash flows from operating activities on the statements of cash flows. Eversource provides retirement and other benefits for certain current and past company officers. These benefits are accounted for on an accrual basis and expensed over a period equal to the service lives of the employees. The actuarially-determined liability for these benefits is included in Other Current and Long-Term Liabilities on the balance sheets. The related expense, which includes the allocation of expense associated with Eversource's service company officers that support CL&P, NSTAR Electric and PSNH, is included in Operations and Maintenance Expense on the income statements. The liability and expense amounts are as follows: Eversource (Millions of Dollars) As of and For the Years Ended December 31, 2019 2018 2017 Actuarially-Determined Liability $ 52.0 $ 49.1 $ 53.4 Other Retirement Benefits Expense 2.7 2.7 2.8 As of and For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Actuarially-Determined Liability $ 0.2 $ 0.1 $ 1.7 $ 0.3 $ 0.1 $ 1.7 $ 0.3 $ 0.1 $ 1.9 Other Retirement Benefits Expense 1.0 0.9 0.4 1.1 1.1 0.4 1.0 1.0 0.5

INCOME TAXES

INCOME TAXES	12 Months Ended
INCOME TAXES	Dec. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The components of income tax expense are as follows: Eversource (Millions of Dollars) For the Years Ended December 31, 2019 2018 2017 Current Income Taxes: Federal $ 56.9 $ 106.5 $ 58.9 State 10.5 10.6 31.6 Total Current 67.4 117.1 90.5 Deferred Income Taxes, Net: Federal 138.4 122.6 433.0 State 71.4 52.2 58.6 Total Deferred 209.8 174.8 491.6 Investment Tax Credits, Net (3.7 ) (2.9 ) (3.2 ) Income Tax Expense $ 273.5 $ 289.0 $ 578.9 For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Current Income Taxes: Federal $ 68.4 $ 82.6 $ 22.9 $ 54.2 $ 79.3 $ 12.2 $ 50.9 $ 107.8 $ 18.6 State 15.4 18.2 2.2 20.9 30.0 (0.5 ) 17.4 25.6 6.2 Total Current 83.8 100.8 25.1 75.1 109.3 11.7 68.3 133.4 24.8 Deferred Income Taxes, Net: Federal 35.2 0.1 5.8 48.5 27.9 15.4 123.9 88.1 52.7 State 18.8 27.0 10.1 6.4 13.5 20.5 (4.6 ) 22.4 11.2 Total Deferred 54.0 27.1 15.9 54.9 41.4 35.9 119.3 110.5 63.9 Investment Tax Credits, Net (0.8 ) (2.6 ) — (0.9 ) (1.8 ) — (1.0 ) (1.8 ) — Income Tax Expense $ 137.0 $ 125.3 $ 41.0 $ 129.1 $ 148.9 $ 47.6 $ 186.6 $ 242.1 $ 88.7 A reconciliation between income tax expense and the expected tax expense at the statutory rate is as follows: Eversource (Millions of Dollars, except percentages) For the Years Ended December 31, 2019 2018 2017 Income Before Income Tax Expense $ 1,190.1 $ 1,329.5 $ 1,574.4 Statutory Federal Income Tax Expense at 21% in 2019 and 2018, and 35% in 2017 249.9 279.2 551.0 Tax Effect of Differences: Depreciation 1.9 (30.8 ) (10.8 ) Investment Tax Credit Amortization (3.7 ) (2.9 ) (3.2 ) State Income Taxes, Net of Federal Impact 24.6 44.4 47.7 Dividends on ESOP (5.1 ) (5.1 ) (8.4 ) Tax Asset Valuation Allowance/Reserve Adjustments 40.1 5.2 7.0 Excess Stock Benefit (1.5 ) (1.5 ) (2.9 ) EDIT Amortization (37.4 ) (5.0 ) — Other, Net 4.7 5.5 (1.5 ) Income Tax Expense $ 273.5 $ 289.0 $ 578.9 Effective Tax Rate 23.0 % 21.7 % 36.8 % For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars, except percentages) CL&P NSTAR PSNH CL&P NSTAR PSNH CL&P NSTAR PSNH Income Before Income Tax Expense $ 547.8 $ 557.3 $ 175.0 $ 506.8 $ 532.0 $ 163.5 $ 563.4 $ 616.8 $ 224.7 Statutory Federal Income Tax Expense at 21% in 2019 and 2018, and 35% in 2017 115.0 117.0 36.8 106.4 111.7 34.3 197.2 215.9 78.6 Tax Effect of Differences: Depreciation (0.2 ) (3.0 ) (0.8 ) (1.2 ) (2.8 ) 0.1 (5.2 ) (3.0 ) 1.1 Investment Tax Credit Amortization (0.8 ) (2.6 ) — (0.9 ) (1.8 ) — (1.0 ) (1.8 ) — State Income Taxes, Net of Federal Impact 2.5 35.7 9.8 14.5 33.2 15.8 4.5 31.2 11.3 Tax Asset Valuation Allowance/Reserve Adjustments 24.5 — — 7.1 1.2 — (9.5 ) — — Excess Stock Benefit (0.5 ) (0.5 ) (0.2 ) (0.1 ) (0.1 ) (0.1 ) (0.7 ) (0.7 ) (0.3 ) EDIT Amortization (5.8 ) (22.9 ) (4.0 ) — — (4.4 ) — — — Other, Net 2.3 1.6 (0.6 ) 3.3 7.5 1.9 1.3 0.5 (2.0 ) Income Tax Expense $ 137.0 $ 125.3 $ 41.0 $ 129.1 $ 148.9 $ 47.6 $ 186.6 $ 242.1 $ 88.7 Effective Tax Rate 25.0 % 22.5 % 23.4 % 25.5 % 28.0 % 29.1 % 33.1 % 39.2 % 39.5 % Eversource, CL&P, NSTAR Electric and PSNH file a consolidated federal income tax return and unitary, combined and separate state income tax returns. These entities are also parties to a tax allocation agreement under which taxable subsidiaries do not pay any more taxes than they would have otherwise paid had they filed a separate company tax return, and subsidiaries generating tax losses, if any, are paid for their losses when utilized. Deferred tax assets and liabilities are recognized for the future tax effects of temporary differences between the carrying amounts and the tax basis of assets and liabilities. The tax effect of temporary differences is accounted for in accordance with the rate-making treatment of the applicable regulatory commissions and relevant accounting authoritative literature. The tax effects of temporary differences that give rise to the net accumulated deferred income tax obligations are as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Deferred Tax Assets: Employee Benefits $ 509.4 $ 125.4 $ 54.8 $ 46.7 $ 388.2 $ 94.5 $ 35.0 $ 31.1 Derivative Liabilities 105.0 103.6 — — 111.4 111.4 — — Regulatory Deferrals - Liabilities 267.0 37.1 165.7 19.0 299.3 38.6 195.5 16.1 Allowance for Uncollectible Accounts 56.7 25.7 17.7 2.8 54.0 23.1 17.8 3.0 Tax Effect - Tax Regulatory Liabilities 830.4 333.5 280.9 111.3 830.3 336.8 288.9 111.7 Net Operating Loss Carryforwards 9.1 — — — 28.5 — — 0.6 Purchase Accounting Adjustment 58.7 — — — 64.2 — — — Other 190.4 92.0 35.8 20.0 166.2 81.1 15.6 33.4 Total Deferred Tax Assets 2,026.7 717.3 554.9 199.8 1,942.1 685.5 552.8 195.9 Less: Valuation Allowance 43.0 24.9 — — 19.5 10.7 — — Net Deferred Tax Assets $ 1,983.7 $ 692.4 $ 554.9 $ 199.8 $ 1,922.6 $ 674.8 $ 552.8 $ 195.9 Deferred Tax Liabilities: Accelerated Depreciation and Other Plant-Related Differences $ 3,901.0 $ 1,362.2 $ 1,391.9 $ 428.9 $ 3,724.2 $ 1,293.3 $ 1,342.4 $ 410.6 Property Tax Accruals 76.8 36.8 29.0 4.7 73.2 35.4 26.3 5.2 Regulatory Amounts: Regulatory Deferrals - Assets 1,155.6 340.7 276.2 260.9 1,025.9 320.1 277.4 213.8 Tax Effect - Tax Regulatory Assets 238.2 171.7 11.7 8.3 238.9 167.0 9.7 8.1 Goodwill Regulatory Asset - 1999 Merger 90.6 — 77.8 — 95.2 — 81.7 — Derivative Assets 19.7 19.7 — — 20.1 19.9 — — Other 257.6 5.9 125.6 3.2 251.1 5.9 109.8 39.4 Total Deferred Tax Liabilities $ 5,739.5 $ 1,937.0 $ 1,912.2 $ 706.0 $ 5,428.6 $ 1,841.6 $ 1,847.3 $ 677.1 2017 Federal Legislation: On December 22, 2017, the Tax Cuts and Jobs Act became law, which amended existing federal tax rules and included numerous provisions that impacted corporations. In particular, the act reduced the U.S. federal corporate income tax rate from 35 percent to 21 percent effective January 1, 2018. For our regulated companies, the most significant changes are (1) the benefit of incurring a lower federal income tax expense and (2) the reduction in ADIT liabilities (now excess ADIT or EDIT), which are estimated to be approximately $2.8 billion and are included in regulatory liabilities as of December 31, 2019 . In 2019, Eversource refunded $51.5 million ( $7.9 million at CL&P, $31.5 million at NSTAR Electric, $5.6 million at PSNH, $1.4 million at Yankee Gas and $5.1 million at NSTAR Gas) to customers. See Note 2, "Regulatory Accounting," to the financial statements for further information. 2019 Federal Legislation: On December 20, 2019, the "Further Consolidated Appropriations Act, 2020," became law, which provided a one-year extension of the production tax credit or the investment tax credit for renewable wind projects under Section 45 of the Internal Revenue Code of 1986 on which construction begins before January 1, 2021. If construction begins on a qualifying wind project in 2020, the project will qualify for a production tax credit of $15 per MWh or an 18 percent investment tax credit. Carryforwards: The following table provides the amounts and expiration dates of state tax credit and loss carryforwards and federal tax credit and net operating loss carryforwards: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR PSNH Expiration Range Eversource CL&P NSTAR PSNH Expiration Range Federal Net $ 19.8 $ — $ — $ — 2033 - 2037 $ 103.6 $ — $ — $ — 2033 - 2037 Federal Charitable — — — — 2020 - 2022 2.2 — — — 2020 - 2022 State Net Operating Loss 65.5 — — — 2020 - 2038 80.7 — — — 2019 - 2038 State Tax Credit 168.1 122.3 — — 2019 - 2024 148.9 107.0 — — 2018 - 2023 State Charitable 9.9 — — — 2019 - 2023 9.6 — — — 2019 - 2023 In 2019, the company increased its valuation allowance reserve for state credits by $18.5 million ( $14.2 million for CL&P), net of tax, to reflect an update for expired tax credits. In 2018, the Company increased its valuation allowance reserve for state credits by $5.2 million ( $4.4 million for CL&P), net of tax, to reflect an update for expired tax credits. For 2019 and 2018, state credit and state loss carryforwards have been partially reserved by a valuation allowance of $43.0 million and $19.5 million (net of tax), respectively. Unrecognized Tax Benefits: A reconciliation of the activity in unrecognized tax benefits, all of which would impact the effective tax rate if recognized, is as follows: (Millions of Dollars) Eversource CL&P Balance as of January 1, 2017 $ 48.4 $ 15.3 Gross Increases - Current Year 11.4 4.7 Gross Decreases - Prior Year (0.9 ) (0.5 ) Lapse of Statute of Limitations (7.2 ) (1.4 ) Balance as of December 31, 2017 51.7 18.1 Gross Increases - Current Year 9.2 3.2 Gross Decreases - Prior Year (6.5 ) (0.9 ) Lapse of Statute of Limitations (8.5 ) (2.2 ) Balance as of December 31, 2018 45.9 18.2 Gross Increases - Current Year 12.1 4.0 Gross Increases - Prior Year 3.4 3.3 Lapse of Statute of Limitations (6.4 ) (2.4 ) Balance as of December 31, 2019 $ 55.0 $ 23.1 Interest and Penalties: Interest on uncertain tax positions is recorded and generally classified as a component of Other Interest Expense on the statements of income. However, when resolution of uncertainties results in the Company receiving interest income, any related interest benefit is recorded in Other Income, Net on the statements of income. No penalties have been recorded. The amount of interest expense/(income) on uncertain tax positions recognized and the related accrued interest payable/(receivable) are as follows: Other Interest Expense/(Income) Accrued Interest Expense For the Years Ended December 31, As of December 31, (Millions of Dollars) 2019 2018 2017 2019 2018 Eversource $ — $ (1.7 ) $ — $ 0.1 $ 0.1 Tax Positions: During 2019 and 2018, Eversource did not resolve any of its uncertain tax positions. Open Tax Years: The following table summarizes Eversource, CL&P, NSTAR Electric and PSNH's tax years that remain subject to examination by major tax jurisdictions as of December 31, 2019 : Description Tax Years Federal 2019 Connecticut 2016 - 2019 Massachusetts 2016 - 2019 New Hampshire 2017 - 2019 Eversource does not estimate to have an earnings impact related to unrecognized tax benefits during the next twelve months.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
COMMITMENTS AND CONTINGENCIES	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES A. Environmental Matters Eversource, CL&P, NSTAR Electric and PSNH are subject to environmental laws and regulations intended to mitigate or remove the effect of past operations and improve or maintain the quality of the environment. These laws and regulations require the removal or the remedy of the effect on the environment of the disposal or release of certain specified hazardous substances at current and former operating sites. Eversource, CL&P, NSTAR Electric and PSNH have an active environmental auditing and training program and each believes it is substantially in compliance with all enacted laws and regulations. Environmental reserves are accrued when assessments indicate it is probable that a liability has been incurred and an amount can be reasonably estimated. The approach used estimates the liability based on the most likely action plan from a variety of available remediation options, including no action required or several different remedies ranging from establishing institutional controls to full site remediation and monitoring. These liabilities are estimated on an undiscounted basis and do not assume that the amounts are recoverable from insurance companies or other third parties. The environmental reserves include sites at different stages of discovery and remediation and do not include any unasserted claims. These reserve estimates are subjective in nature as they take into consideration several different remediation options at each specific site. The reliability and precision of these estimates can be affected by several factors, including new information concerning either the level of contamination at the site, the extent of Eversource's, CL&P's, NSTAR Electric's and PSNH's responsibility for remediation or the extent of remediation required, recently enacted laws and regulations or changes in cost estimates due to certain economic factors. It is possible that new information or future developments could require a reassessment of the potential exposure to required environmental remediation. As this information becomes available, management will continue to assess the potential exposure and adjust the reserves accordingly. The amounts recorded as environmental reserves are included in Other Current Liabilities and Other Long-Term Liabilities on the balance sheets and represent management's best estimate of the liability for environmental costs, and take into consideration site assessment, remediation and long-term monitoring costs. The environmental reserves also take into account recurring costs of managing hazardous substances and pollutants, mandated expenditures to remediate contaminated sites and any other infrequent and non-recurring clean-up costs. A reconciliation of the activity in the environmental reserves is as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Balance as of January 1, 2018 $ 54.9 $ 4.7 $ 2.7 $ 5.7 Additions 23.5 1.9 9.7 — Payments/Reductions (13.7 ) (1.2 ) (1.5 ) (0.3 ) Balance as of December 31, 2018 64.7 5.4 10.9 5.4 Additions 26.5 7.0 0.5 2.8 Payments/Reductions (10.2 ) (1.0 ) (3.4 ) (0.7 ) Balance as of December 31, 2019 $ 81.0 $ 11.4 $ 8.0 $ 7.5 The number of environmental sites for which remediation or long-term monitoring, preliminary site work or site assessment is being performed are as follows: Eversource CL&P NSTAR Electric PSNH 2019 57 15 15 9 2018 60 15 16 9 The increase in the reserve balance was due primarily to changes in cost estimates at certain MGP sites at the natural gas companies, at CL&P and at PSNH, for which additional remediation will be required. Included in the number of sites and reserve amounts above are former MGP sites that were operated several decades ago and manufactured natural gas from coal and other processes, which resulted in certain by-products remaining in the environment that may pose a potential risk to human health and the environment, for which Eversource may have potential liability. The reserve balances related to these former MGP sites were $67.9 million and $50.1 million as of December 31, 2019 and 2018, respectively, and related primarily to the natural gas business segment. As of December 31, 2019 , for 6 environmental sites ( 1 for CL&P) that are included in the Company's reserve for environmental costs, the information known and the nature of the remediation options allow for the Company to estimate the range of losses for environmental costs. As of December 31, 2019 , $35.9 million (including $0.4 million for CL&P) had been accrued as a liability for these sites, which represents the low end of the range of the liabilities for environmental costs. Management believes that additional losses of up to approximately $35 million ( $0.5 million at CL&P) may be incurred in executing current remediation plans for these sites. As of December 31, 2019 , for 15 environmental sites ( 7 for CL&P and 4 for NSTAR Electric) that are included in the Company's reserve for environmental costs, management cannot reasonably estimate the exposure to loss in excess of the reserve, or range of loss, as these sites are under investigation and/or there is significant uncertainty as to what remedial actions, if any, the Company may be required to undertake. As of December 31, 2019 , $7.4 million (including $2.3 million for CL&P and $1.9 million for NSTAR Electric) had been accrued as a liability for these sites. As of December 31, 2019 , for the remaining 36 environmental sites (including 7 for CL&P, 11 for NSTAR Electric and 9 for PSNH) that are included in the Company's reserve for environmental costs, the $37.7 million accrual (including $8.7 million for CL&P, $6.1 million for NSTAR Electric and $7.5 million for PSNH) represents management's best estimate of the probable liability and no additional loss is anticipated at this time. Estimated Future Annual Costs: The estimated future annual costs of significant executed, non-cancelable, long-term contractual arrangements in effect as of December 31, 2019 are as follows: Eversource (Millions of Dollars) 2020 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 614.6 $ 594.3 $ 651.7 $ 629.1 $ 624.8 $ 3,590.6 $ 6,705.1 Purchased Power and Capacity 73.5 69.0 75.1 81.6 75.9 71.5 446.6 Peaker CfDs 22.4 23.0 16.9 20.1 15.5 29.8 127.7 Natural Gas Procurement 266.2 255.3 202.8 166.7 165.7 1,093.3 2,150.0 Transmission Support Commitments 22.1 — — — — — 22.1 Total $ 998.8 $ 941.6 $ 946.5 $ 897.5 $ 881.9 $ 4,785.2 $ 9,451.5 CL&P (Millions of Dollars) 2020 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 457.3 $ 459.6 $ 514.4 $ 516.2 517.4 2,790.6 $ 5,255.5 Purchased Power and Capacity 69.8 65.3 71.4 78.0 72.9 55.5 412.9 Peaker CfDs 22.4 23.0 16.9 20.1 15.5 29.8 127.7 Transmission Support Commitments 8.7 — — — — — 8.7 Total $ 558.2 $ 547.9 $ 602.7 $ 614.3 $ 605.8 $ 2,875.9 $ 5,804.8 NSTAR Electric (Millions of Dollars) 2020 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 95.5 $ 91.2 $ 91.4 $ 66.6 $ 63.8 $ 418.1 $ 826.6 Purchased Power and Capacity 3.1 3.1 3.1 3.0 3.0 16.0 31.3 Transmission Support Commitments 8.7 — — — — — 8.7 Total $ 107.3 $ 94.3 $ 94.5 $ 69.6 $ 66.8 $ 434.1 $ 866.6 PSNH (Millions of Dollars) 2020 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 61.8 $ 43.5 $ 45.9 $ 46.3 $ 43.6 $ 381.9 $ 623.0 Purchased Power and Capacity 0.6 0.6 0.6 0.6 — — 2.4 Transmission Support Commitments 4.7 — — — — — 4.7 Total $ 67.1 $ 44.1 $ 46.5 $ 46.9 $ 43.6 $ 381.9 $ 630.1 Renewable Energy: Renewable energy contracts include non-cancellable commitments under contracts of CL&P, NSTAR Electric and PSNH for the purchase of energy and capacity from renewable energy facilities. Such contracts extend through 2039 for CL&P, 2040 for NSTAR Electric and 2033 for PSNH. On December 28, 2018 , under Public Act 17-3, "An Act Concerning Zero Carbon Procurement," DEEP selected the Millstone Nuclear Power Station generation facility and Seabrook Nuclear Power Plant, along with smaller generation facilities, in DEEP’s zero-carbon request for proposal. CL&P and UI were directed by DEEP to enter into ten -year contracts to purchase a combined total of approximately 9 million MWh annually from the Millstone generation facility. On March 15, 2019 , CL&P and UI each signed a ten -year contract with the owner of Millstone Nuclear Power Station in order to purchase a combined amount of approximately 50 percent of the facility's output (approximately 40 percent by CL&P). The Millstone Nuclear Power Station has a 2,112 MW nameplate capacity. PURA approved the contracts on September 18, 2019. Energy deliveries and payments under these contracts began in the fourth quarter of 2019. CL&P and UI were also directed by DEEP to enter into eight -year contracts to purchase a combined amount of approximately 18 percent of the facility's output (approximately 15 percent by CL&P), from the Seabrook Nuclear Power Plant beginning January 1, 2022. The Seabrook Nuclear Power Plant has an approximate 1,250 MW nameplate capacity. On November 22, 2019 , CL&P and UI each signed an eight -year contract with the owner of the Seabrook Nuclear Power Plant. PURA approved the contracts on November 27, 2019. The total estimated cost of the Millstone Nuclear Power Station and Seabrook Nuclear Power Plant energy purchase contracts are $4.1 billion and are reflected in the table above. CL&P sells the energy purchased under these contracts into the market and uses the proceeds from these energy sales to offset the contract costs. As the net costs under these contracts are recovered from customers in future rates, the contracts do not have an impact on the net income of CL&P. These new contracts do not meet the definition of a derivative, and accordingly, the costs of these contracts are being accounted for as incurred. The contractual obligations table above does not include long-term commitments signed by CL&P and NSTAR Electric, as required by the PURA and DPU, respectively, for the purchase of renewable energy and related products that are contingent on the future construction of energy facilities. Purchased Power and Capacity: These contracts include capacity CfDs of CL&P through 2026, and various IPP contracts or purchase obligations for electricity which extend through 2024 for CL&P, 2031 for NSTAR Electric and 2023 for PSNH. CL&P, along with UI, has three capacity CfDs for a total of approximately 676 MW of capacity consisting of two generation units and one demand response project. The capacity CfDs extend through 2026 and obligate both CL&P and UI to make or receive payments on a monthly basis to or from the generation facilities based on the difference between a set contractual capacity price and the capacity market prices received by the generation facilities in the ISO-NE capacity markets. CL&P has a sharing agreement with UI, whereby UI shares 20 percent of the costs and benefits of these contracts. CL&P's portion of the costs and benefits of these contracts will be paid by, or refunded to, CL&P's customers. The contractual obligations table above does not include CL&P's, NSTAR Electric's or PSNH's standard/basic service contracts for the purchase of energy supply, the amounts of which vary with customers' energy needs. Peaker CfDs: CL&P, along with UI, has three peaker CfDs for a total of approximately 500 MW of peaking capacity through 2042. CL&P has a sharing agreement with UI, whereby CL&P is responsible for 80 percent and UI for 20 percent of the net costs or benefits of these CfDs. The Peaker CfDs pay the generation facility owner the difference between capacity, forward reserve and energy market revenues and a cost-of-service payment stream for 30 years. The ultimate cost or benefit to CL&P under these contracts will depend on the costs of plant operation and the prices that the projects receive for capacity and other products in the ISO-NE markets. CL&P's portion of the amounts paid or received under the Peaker CfDs will be recoverable from, or refunded to, CL&P's customers. Natural Gas Procurement: Eversource's natural gas distribution businesses have long-term contracts for the purchase, transportation and storage of natural gas as part of its portfolio of supplies, which extend through 2038. Transmission Support Commitments: Along with other New England utilities, CL&P, NSTAR Electric and PSNH entered into agreements in 1985 to support transmission and terminal facilities that were built to import electricity from the Hydro-Québec system in Canada. CL&P, NSTAR Electric and PSNH are obligated to pay, over a 30 -year period ending in 2020, their proportionate shares of the annual operation and maintenance expenses and capital costs of those facilities. Future transmission support agreements beginning in the second half of 2020 are under negotiation. The total costs incurred under these agreements were as follows: Eversource For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Renewable Energy $ 320.8 $ 218.5 $ 235.5 Purchased Power and Capacity 62.1 72.0 103.9 Peaker CfDs 13.0 20.9 38.7 Natural Gas Procurement 448.5 432.4 377.0 Transmission Support Commitments 21.8 23.4 19.8 Coal, Wood and Other (1) — — 47.7 For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR PSNH CL&P NSTAR PSNH CL&P NSTAR PSNH Renewable Energy $ 160.6 $ 89.9 $ 70.3 $ 63.2 $ 89.8 $ 65.5 $ 51.0 $ 123.7 $ 60.8 Purchased Power and Capacity 50.4 5.1 6.6 49.4 4.4 18.2 81.0 4.0 18.9 Peaker CfDs 13.0 — — 20.9 — — 38.7 — — Transmission Support Commitments 8.6 8.6 4.6 9.2 9.2 5.0 7.8 7.8 4.2 Coal, Wood and Other (1) — — — — — — — — 47.7 (1) CL&P, NSTAR Electric and PSNH have plant closure and fuel storage cost obligations to the Yankee Companies, which have each completed the physical decommissioning of their respective nuclear power facilities and are now engaged in the long-term storage of their spent fuel. The Yankee Companies fund these costs through litigation proceeds received from the DOE and, to the extent necessary, through wholesale, FERC-approved rates charged under power purchase agreements with several New England utilities, including CL&P, NSTAR Electric and PSNH. CL&P, NSTAR Electric and PSNH, in turn recover these costs from their customers through state regulatory commission-approved retail rates. The Yankee Companies collect amounts that management believes are adequate to recover the remaining plant closure and fuel storage cost estimates for the respective plants. Management believes CL&P and NSTAR Electric will recover their shares of these obligations from their customers. PSNH has recovered its total share of these costs from its customers. Spent Nuclear Fuel Litigation: The Yankee Companies have filed complaints against the DOE in the Court of Federal Claims seeking monetary damages resulting from the DOE's failure to accept delivery of, and provide for a permanent facility to store, spent nuclear fuel pursuant to the terms of the 1983 spent fuel and high-level waste disposal contracts between the Yankee Companies and the DOE. The court previously awarded the Yankee Companies damages for Phases I, II and III of litigation resulting from the DOE's failure to meet its contractual obligations. These Phases covered damages incurred in the years 1998 through 2012, and the awarded damages have been received by the Yankee Companies with certain amounts of the damages refunded to their customers. DOE Phase IV Damages - On May 22, 2017, each of the Yankee Companies filed a fourth set of lawsuits against the DOE in the Court of Federal Claims. The Yankee Companies sought monetary damages totaling $104.4 million for CYAPC, YAEC and MYAPC, resulting from the DOE's failure to begin accepting spent nuclear fuel for disposal covering the years from 2013 to 2016 (“DOE Phase IV”). On February 21, 2019, the Yankee Companies received a partial summary judgment and partial final judgment in their favor for the undisputed amount of monetary damages of $103.2 million . The court awarded CYAPC, YAEC, and MYAPC damages of $40.7 million , $28.1 million and $34.4 million , respectively. The DOE did not appeal the court's judgment and the decision became final on April 23, 2019. On June 12, 2019, each of the Yankee Companies received the damages proceeds. On June 12, 2019, the court accepted an offer of judgment in the amount of $0.5 million to settle the disputed amount of approximately $1 million in Phase IV contested damages. The Yankee Companies received the $0.5 million payment in July 2019. CYAPC's and YAEC's proceeds received were classified as operating activities on the Eversource consolidated statement of cash flows. In September 2019, the Yankee Companies made a required informational filing with FERC as to the use of proceeds, for which approval was received in the fourth quarter of 2019. In December 2019, YAEC and MYAPC returned proceeds of $5.4 million and $21.0 million , respectively, to its member companies, of which the Eversource utilities (CL&P, NSTAR Electric and PSNH) received a total of $2.8 million from YAEC and $5.0 million from MYAPC. The Eversource utilities will ultimately refund these proceeds to utility customers. Also, in December 2019, CYAPC paid $29.0 million In the normal course of business, Eversource parent provides credit assurances on behalf of its subsidiaries, including CL&P, NSTAR Electric and PSNH, in the form of guarantees. Management does not anticipate a material impact to net income or cash flows as a result of these various guarantees and indemnifications. The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries and affiliates to external parties as of December 31, 2019 : Company Description Maximum Exposure (in millions) Expiration Dates Various Surety Bonds (1) $ 29.2 2020 - 2021 Rocky River Realty Company and Eversource Service Lease Payments for Real Estate 6.5 2024 Bay State Wind LLC Real Estate Purchase 2.5 2020 Sunrise Wind LLC Offshore Wind (2) 2.2 — (1) Surety bond expiration dates reflect termination dates, the majority of which will be renewed or extended. Certain surety bonds contain credit ratings triggers that would require Eversource parent to post collateral in the event that the unsecured debt credit ratings of Eversource parent are downgraded. (2) On October 25, 2019, Eversource parent issued a guaranty on behalf of its 50 percent -owned affiliate, Sunrise Wind LLC, whereby Eversource parent will guaranty Sunrise Wind LLC's performance of certain obligations, in an amount not to exceed $15.4 million , under the Offshore Wind Renewable Energy Certificate Purchase and Sale Agreement (the Agreement). The Agreement was executed on October 25, 2019, by and between NYSERDA and Sunrise Wind LLC. Obligations of Eversource parent under the guaranty expire at such time as the guaranteed obligations have been fully performed. The Company regularly reviews performance risk under this arrangement, and in the event it becomes probable that Eversource parent will be required to perform under the guarantee, the amount of probable payment will be recorded. As of December 31, 2019, the fair value of the guarantee was immaterial. Eversource parent issued a guaranty on behalf of its subsidiary, NPT, under which, beginning at the time the Northern Pass Transmission line would go into commercial operation, Eversource parent would guarantee the financial obligations of NPT under the TSA with HQ in an amount not to exceed $25 million . Eversource parent's obligations under the guaranty expire upon the full, final and indefeasible payment of the guaranteed obligations. In the second quarter of 2019, Eversource concluded that construction of the NPT project was no longer probable. For further information regarding the impairment of NPT, see Note 1D, "Summary of Significant Accounting Policies - Impairment of Northern Pass Transmission," to the financial statements. While this guaranty is currently outstanding, it is expected to be extinguished in connection with the final dissolution of NPT. Four separate complaints were filed at the FERC by combinations of New England state attorneys general, state regulatory commissions, consumer advocates, consumer groups, municipal parties and other parties (collectively, the Complainants). In each of the first three complaints, filed on October 1, 2011, December 27, 2012, and July 31, 2014, respectively, the Complainants challenged the NETOs' base ROE of 11.14 percent that had been utilized since 2005 and sought an order to reduce it prospectively from the date of the final FERC order and for the separate 15 -month complaint periods. In the fourth complaint, filed April 29, 2016, the Complainants challenged the NETOs' base ROE billed of 10.57 percent and the maximum ROE for transmission incentive (incentive cap) of 11.74 percent , asserting that these ROEs were unjust and unreasonable. The ROE originally billed during the period October 1, 2011 (beginning of the first complaint period) through October 15, 2014 consisted of a base ROE of 11.14 percent and incentives up to 13.1 percent . On October 16, 2014, the FERC set the base ROE at 10.57 percent and the incentive cap at 11.74 percent for the first complaint period. This was also effective for all prospective billings to customers beginning October 16, 2014. This FERC order was vacated on April 14, 2017 by the U.S. Court of Appeals for the D.C. Circuit (the Court). All amounts associated with the first complaint period have been refunded, which totaled $38.9 million (pre-tax and excluding interest) at Eversource and reflected both the base ROE and incentive cap prescribed by the FERC order. The refund consisted of $22.4 million for CL&P, $13.7 million for NSTAR Electric and $2.8 million for PSNH. Eversource has recorded a reserve of $39.1 million (pre-tax and excluding interest) for the second complaint period as of December 31, 2019 . This reserve represents the difference between the billed rates during the second complaint period and a 10.57 percent base ROE and 11.74 percent incentive cap. The reserve consisted of $21.4 million for CL&P, $14.6 million for NSTAR Electric and $3.1 million for PSNH as of December 31, 2019 . On October 16, 2018, FERC issued an order on all four complaints describing how it intends to address the issues that were remanded by the Court. FERC proposed a new framework to determine (1) whether an existing ROE is unjust and unreasonable and, if so, (2) how to calculate a replacement ROE. Initial briefs were filed by the NETOs, Complainants and FERC Trial Staff on January 11, 2019 and reply briefs were filed on March 8, 2019. The NETOs' brief was supportive of the overall ROE methodology determined in the October 16, 2018 order provided the FERC does not change the proposed methodology or alter its implementation in a manner that has a material impact on the results. The FERC order included illustrative calculations for the first complaint using FERC's proposed frameworks with financial data from that complaint. Those illustrative calculations indicated that for the first complaint period, for the NETOs, which FERC concludes are of average financial risk, the preliminary just and reasonable base ROE is 10.41 percent and the preliminary incentive cap on total ROE is 13.08 percent . If the results of the illustrative calculations were included in a final FERC order for each of the complaint periods, then a 10.41 percent base ROE and a 13.08 percent incentive cap would not have a significant impact on our financial statements for all of the complaint periods. These preliminary calculations are not binding and do not represent what we believe to be the most likely outcome of a final FERC order. On November 21, 2019, FERC issued an order concerning the transmission ROEs for the Midcontinent ISO transmission owners (MISO). In that order, FERC adopted another new methodology for determining base ROEs for MISO, which differed significantly from the methodology and framework set forth in its October 16, 2018 FERC order on the NETOs’ ROE dockets. On December 23, 2019, the NETOs filed a Supplemental Paper Hearing Brief and a Motion to supplement the record in the NETO ROE dockets to respond to the new methodology proposed in the MISO order, as there is uncertainty to whether it may be applied to the NETOs’ cases. On January 21, 2020, the FERC issued an order granting rehearing for further consideration to give the FERC more time to act on the substantive issues of the MISO ROE proceedings. Further changes to the methodology by FERC are possible as a result of the arguments in both the MISO and NETO proceedings. Given the significant uncertainty relating to the October 2018 FERC order, the November 2019 FERC order to MISO, and the FERC's rehearing of the MISO order, the Company is unable to predict the potential effect of the MISO order on the NETO complaints or the outcome of the four complaints and concluded that there is no reasonable basis for a change to the reserve or recognized ROEs for any of the complaint periods at this time. Further, the Company cannot reasonably estimate a range of gain or loss for any of the four complaint proceedings. Eversource, CL&P, NSTAR Electric and PSNH currently record revenues at the 10.57 percent base ROE and incentive cap at 11.74 percent established in the October 16, 2014 FERC order. A change of 10 basis points to the base ROE used to establish the reserves would impact Eversource’s after-tax earnings by an average of approximately $3 million for each of the four 15-month complaint periods. F. Eversource and NSTAR Electric Boston Harbor Civil Action On July 15, 2016, the United States Attorney on behalf of the United States Army Corps of Engineers filed a civil action in the United States District Court for the District of Massachusetts under provisions of the Rivers and Harbors Act of 1899 and the Clean Water Act against NSTAR Electric, HEEC, and the Massachusetts Water Resources Authority (together with NSTAR Electric and HEEC, the Defendants). The action alleged that the Defendants failed to comply with certain permitting requirements related to the placement of the HEEC-owned electric distribution cable beneath Boston Harbor. The action sought an order to compel HEEC to comply with cable depth requirements in the United States Army Corps of Engineers' permit or alternatively to remove the electric distribution cable and cease unauthorized work in U.S. waterways. The action also sought civil penalties and other costs. The parties reached a settlement pursuant to which HEEC agreed to install a new 115 kV distribution cable across Boston Harbor to Deer Island, utilizing a different route, and remove portions of the existing cable. Upon the installation and completion of the new cable and the removal of the portions of the existing cable, all issues surrounding the current permit from the United States Army Corps of Engineers are expected to be resolved, and such litigation is expected to be dismissed with prejudice. Construction of the new distribution cable was completed in August 2019 and removal of the portions of the existing cable was completed in January 2020. NSTAR Electric agreed to provide a rate base credit of $17.5 million to the Massachusetts Water Resources Authority for the new cable. This negotiated credit resulted in the initial $17.5 million of construction costs on the new cable being expensed as incurred, all of which was fully expensed in 2018. In connection with the new cable that was placed into service, a corresponding ARO was recognized for approximately $32 million within Other Long-Term Liabilities on the Eversource and NSTAR Electric balance sheets as of December 31, 2019. For further information on the ARO, see Note 7, "Asset Retirement Obligations," to the financial statements. G. Litigation and Legal Proceedings Eversource, including CL&P, NSTAR Electric and PSNH, are involved in legal, tax and regulatory proceedings regarding matters arising in the ordinary course of business, which involve management's assessment to determine the probability of whether a loss will occur and, if probable, its best estimate of probable loss. The Company records and discloses losses when these losses are probable and reasonably estimable, and discloses matters when losses are probable but not estimable or when losses are reasonably possible. Legal costs related to the defense of loss contingencies are expensed as incurred.

GENERATION ASSET SALE

GENERATION ASSET SALE	12 Months Ended
GENERATION ASSET SALE	Dec. 31, 2019
Regulated Operations [Abstract]
GENERATION ASSET SALE	GENERATION ASSET SALE On January 10, 2018, PSNH completed the sale of its thermal generation assets. The original purchase price of $175 million was adjusted to reflect working capital adjustments, closing date adjustments and proration of taxes and fees prior to closing. As a result of these adjustments, net proceeds from the sale of the thermal assets totaled $116.8 million . On August 26, 2018, PSNH completed the sale of its hydroelectric generation assets. The original purchase price of $83 million was adjusted to reflect contractual adjustments totaling $5.8 million , resulting in net proceeds of $77.2 million . The difference between the carrying value of the hydroelectric generation assets and the sale proceeds resulted in a gain of $17.3 million . An estimated gain from the sale of these assets was included as an offset to the total remaining costs associated with the sale of generation assets that were securitized on May 8, 2018. On May 8, 2018, PSNH Funding issued $635.7 million of securitized RRBs to finance PSNH's unrecovered remaining costs resulting from the divestiture of its generation assets, which included the deferred costs resulting from the sale of the thermal generation assets. These RRBs are secured by a non-bypassable charge recoverable from PSNH customers. PSNH recorded regulatory assets and other deferred costs in connection with the generation asset divestiture and the securitization of remaining costs, which are probable of recovery through collection of the non-bypassable charge. As of December 31, 2019 and 2018, unamortized securitized stranded costs totaled $565.3 million and $608.4 million , respectively, and are included in Regulatory Assets on the Eversource and PSNH balance sheets. For further information on the securitized RRB issuance, see Note 10, "Rate Reduction Bonds and Variable Interest Entities." On November 27, 2019, PSNH filed a motion for the commencement of audit of divestiture-related costs. PSNH’s actual balance of costs eligible for recovery as divestiture-related costs is $654.0 million , which is above the $635.7 million amount securitized in May 2018. PSNH proposed to recover this balance through the SCRC tracker mechanism and believes the amount deferred is probable of recovery. These deferred costs are recorded in Other Long-Term Assets on the balance sheet. For the year ended December 31, 2018, pre-tax income associated with the hydroelectric assets prior to the sale on August 26, 2018 was $9.9 million . For the year ended December 31, 2017, pre-tax income associated with PSNH's generation assets was $60.0 million . As of December 31, 2018, all generation assets had been sold.

LEASES

LEASES	12 Months Ended
LEASES	Dec. 31, 2019
Leases [Abstract]
LEASES	LEASES Eversource, including CL&P, NSTAR Electric and PSNH, has entered into lease agreements as a lessee for the use of land, office space, service centers, vehicles, information technology, and equipment. These lease agreements are classified as either finance or operating leases and the liability and right-of-use asset are recognized on the balance sheet at lease commencement. Leases with an initial term of 12 months or less are not recorded on the balance sheet and are recognized as lease expense on a straight-line basis over the lease term. Eversource determines whether or not a contract contains a lease based on whether or not it provides Eversource with the use of a specifically identified asset for a period of time, as well as both the right to direct the use of that asset and receive the significant economic benefits of the asset. Eversource has elected the practical expedient to not separate non-lease components from lease components and instead to account for both as a single lease component, with the exception of the information technology asset class where the lease and non-lease components are separated. The provisions of Eversource, CL&P, NSTAR Electric and PSNH lease agreements contain renewal options. The renewal options range from one year to twenty years . The renewal period is included in the measurement of the lease liability if it is reasonably certain that Eversource will exercise these renewal options. For leases entered into or modified after the January 1, 2019 implementation date, the discount rate utilized for classification and measurement purposes as of the inception date of the lease is based on each company's collateralized incremental interest rate to borrow over a comparable term for an individual lease because the rate implicit in the lease is not determinable. CL&P and PSNH entered into certain contracts for the purchase of energy that qualify as leases. These contracts do not have minimum lease payments and therefore are not recognized as a lease liability on the balance sheet and are not reflected in the future minimum lease payments table below. Expense related to these contracts is included as variable lease cost in the table below. The expense and long-term obligation for these contracts are also included in Note 13B, "Commitments and Contingencies - Long-Term Contractual Arrangements," to the financial statements. The components of lease cost, prior to amounts capitalized, are as follows: For the Year Ended December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Financing Lease Cost: Amortization of Right-of-use-Assets $ 1.7 $ 0.7 $ 0.2 $ 0.1 Interest on Lease Liabilities 1.2 0.6 0.6 — Total Finance Lease Cost 2.9 1.3 0.8 0.1 Operating Lease Cost 11.7 0.5 3.4 0.1 Variable Lease Cost 60.5 13.3 — 47.2 Total Lease Cost $ 75.1 $ 15.1 $ 4.2 $ 47.4 Operating lease rental payments charged to expense in 2018 and 2017 (which exclude CL&P's and PSNH's energy purchase contracts) were as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2018 $ 10.8 $ 10.9 $ 11.8 $ 2.5 2017 10.5 11.7 11.3 3.3 Operating lease cost, net of the capitalized portion, is included in Operations and Maintenance (or Purchased Power, Fuel and Transmission expense for transmission segment leases) on the statements of income. Amortization of finance lease assets is included in Depreciation on the statements of income. Interest expense on finance leases is included in Interest Expense on the statements of income. Supplemental balance sheet information related to leases is as follows: As of December 31, 2019 (Millions of Dollars) Balance Sheet Classification Eversource CL&P NSTAR Electric PSNH Operating Leases: Operating Lease Right-of-use-Assets, Net Other Long-Term Assets $ 49.9 $ 0.7 $ 24.2 $ 0.4 Operating Lease Liabilities Operating Lease Liabilities - Current Portion Other Current Liabilities $ 8.6 $ 0.5 $ 0.7 $ 0.1 Operating Lease Liabilities - Long-Term Other Long-Term Liabilities 41.3 0.2 23.5 0.3 Total Operating Lease Liabilities $ 49.9 $ 0.7 $ 24.2 $ 0.4 Finance Leases: Finance Lease Right-of-use-Assets, Net Property, Plant and Equipment, Net $ 8.2 $ 1.9 $ 3.3 $ 0.9 Finance Lease Liabilities Finance Lease Liabilities - Current Portion Other Current Liabilities $ 2.4 $ 1.6 $ — $ 0.1 Finance Lease Liabilities - Long-Term Other Long-Term Liabilities 8.1 1.4 4.4 0.8 Total Finance Lease Liabilities $ 10.5 $ 3.0 $ 4.4 $ 0.9 The finance lease payments that NSTAR Electric will make over the next twelve months are entirely interest-related, due to escalating payments. As such, none of the finance lease payments over the next twelve months will reduce the finance lease liability. Other information related to leases is as follows (in millions of dollars, unless otherwise noted): Eversource CL&P NSTAR Electric PSNH As of December 31, 2019 Weighted-Average Remaining Lease Term (Years): Operating Leases 12 2 20 9 Finance Leases 12 2 22 9 Weighted-Average Discount Rate (Percentage): Operating Leases 3.9 % 2.5 % 4.1 % 3.7 % Finance Leases 4.0 % 10.5 % 2.9 % 3.5 % Eversource CL&P NSTAR Electric PSNH For the Year Ended December 31, 2019 Cash Paid for Amounts Included in the Measurement of Lease Liabilities: Operating Cash Flows from Operating Leases $ 11.4 $ 0.4 $ 1.6 $ 0.1 Operating Cash Flows from Finance Leases 1.2 0.6 0.6 — Financing Cash Flows from Finance Leases 2.6 1.4 — 0.1 Supplemental Non-Cash Information on Lease Liabilities: Right-of-use-Assets Obtained in Exchange for New Operating Lease Liabilities 2.9 1.0 0.1 0.2 Right-of-use-Assets Obtained in Exchange for New Finance Lease Liabilities 2.0 — — — Future minimum lease payments, excluding variable costs, under long-term leases, as of December 31, 2019 are as follows: Operating Leases Finance Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Year Ending December 31, 2020 $ 10.2 $ 0.5 $ 1.8 $ 0.1 $ 3.4 $ 2.0 $ 0.6 $ 0.1 2021 9.0 0.2 1.6 0.1 2.9 1.5 0.6 0.1 2022 7.4 — 1.6 0.1 1.5 — 0.6 0.1 2023 4.9 — 1.6 — 0.8 — 0.6 0.1 2024 2.8 — 1.7 — 0.8 — 0.7 0.1 Thereafter 28.9 0.1 28.7 0.2 13.1 — 12.6 0.5 Future lease payments 63.2 0.8 37.0 0.5 22.5 3.5 15.7 1.0 Less amount representing interest 13.3 0.1 12.8 0.1 12.0 0.5 11.3 0.1 Present value of future minimum lease payments $ 49.9 $ 0.7 $ 24.2 $ 0.4 $ 10.5 $ 3.0 $ 4.4 $ 0.9 At December 31, 2018, future minimum rental payments, excluding executory costs, such as property taxes, state use taxes, insurance, and maintenance were as follows: Operating Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 11.5 $ 1.5 $ 7.2 $ 0.5 2020 9.8 1.4 6.0 0.4 2021 8.7 1.2 5.3 0.4 2022 7.2 1.1 4.4 0.4 2023 4.7 0.5 3.1 0.2 Thereafter 32.7 0.2 29.5 0.3 Future minimum lease payments $ 74.6 $ 5.9 $ 55.5 $ 2.2 Capital Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 3.4 $ 2.0 $ 0.5 $ 0.1 2020 3.4 2.0 0.5 0.1 2021 2.9 1.5 0.5 0.1 2022 1.5 — 0.6 0.1 2023 0.7 — 0.6 0.1 Thereafter 13.9 — 13.4 0.5 Future minimum lease payments 25.8 5.5 16.1 1.0 Less amount representing interest 13.8 1.0 12.4 0.1 Present value of future minimum lease payments $ 12.0 $ 4.5 $ 3.7 $ 0.9
LEASES	LEASES Eversource, including CL&P, NSTAR Electric and PSNH, has entered into lease agreements as a lessee for the use of land, office space, service centers, vehicles, information technology, and equipment. These lease agreements are classified as either finance or operating leases and the liability and right-of-use asset are recognized on the balance sheet at lease commencement. Leases with an initial term of 12 months or less are not recorded on the balance sheet and are recognized as lease expense on a straight-line basis over the lease term. Eversource determines whether or not a contract contains a lease based on whether or not it provides Eversource with the use of a specifically identified asset for a period of time, as well as both the right to direct the use of that asset and receive the significant economic benefits of the asset. Eversource has elected the practical expedient to not separate non-lease components from lease components and instead to account for both as a single lease component, with the exception of the information technology asset class where the lease and non-lease components are separated. The provisions of Eversource, CL&P, NSTAR Electric and PSNH lease agreements contain renewal options. The renewal options range from one year to twenty years . The renewal period is included in the measurement of the lease liability if it is reasonably certain that Eversource will exercise these renewal options. For leases entered into or modified after the January 1, 2019 implementation date, the discount rate utilized for classification and measurement purposes as of the inception date of the lease is based on each company's collateralized incremental interest rate to borrow over a comparable term for an individual lease because the rate implicit in the lease is not determinable. CL&P and PSNH entered into certain contracts for the purchase of energy that qualify as leases. These contracts do not have minimum lease payments and therefore are not recognized as a lease liability on the balance sheet and are not reflected in the future minimum lease payments table below. Expense related to these contracts is included as variable lease cost in the table below. The expense and long-term obligation for these contracts are also included in Note 13B, "Commitments and Contingencies - Long-Term Contractual Arrangements," to the financial statements. The components of lease cost, prior to amounts capitalized, are as follows: For the Year Ended December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Financing Lease Cost: Amortization of Right-of-use-Assets $ 1.7 $ 0.7 $ 0.2 $ 0.1 Interest on Lease Liabilities 1.2 0.6 0.6 — Total Finance Lease Cost 2.9 1.3 0.8 0.1 Operating Lease Cost 11.7 0.5 3.4 0.1 Variable Lease Cost 60.5 13.3 — 47.2 Total Lease Cost $ 75.1 $ 15.1 $ 4.2 $ 47.4 Operating lease rental payments charged to expense in 2018 and 2017 (which exclude CL&P's and PSNH's energy purchase contracts) were as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2018 $ 10.8 $ 10.9 $ 11.8 $ 2.5 2017 10.5 11.7 11.3 3.3 Operating lease cost, net of the capitalized portion, is included in Operations and Maintenance (or Purchased Power, Fuel and Transmission expense for transmission segment leases) on the statements of income. Amortization of finance lease assets is included in Depreciation on the statements of income. Interest expense on finance leases is included in Interest Expense on the statements of income. Supplemental balance sheet information related to leases is as follows: As of December 31, 2019 (Millions of Dollars) Balance Sheet Classification Eversource CL&P NSTAR Electric PSNH Operating Leases: Operating Lease Right-of-use-Assets, Net Other Long-Term Assets $ 49.9 $ 0.7 $ 24.2 $ 0.4 Operating Lease Liabilities Operating Lease Liabilities - Current Portion Other Current Liabilities $ 8.6 $ 0.5 $ 0.7 $ 0.1 Operating Lease Liabilities - Long-Term Other Long-Term Liabilities 41.3 0.2 23.5 0.3 Total Operating Lease Liabilities $ 49.9 $ 0.7 $ 24.2 $ 0.4 Finance Leases: Finance Lease Right-of-use-Assets, Net Property, Plant and Equipment, Net $ 8.2 $ 1.9 $ 3.3 $ 0.9 Finance Lease Liabilities Finance Lease Liabilities - Current Portion Other Current Liabilities $ 2.4 $ 1.6 $ — $ 0.1 Finance Lease Liabilities - Long-Term Other Long-Term Liabilities 8.1 1.4 4.4 0.8 Total Finance Lease Liabilities $ 10.5 $ 3.0 $ 4.4 $ 0.9 The finance lease payments that NSTAR Electric will make over the next twelve months are entirely interest-related, due to escalating payments. As such, none of the finance lease payments over the next twelve months will reduce the finance lease liability. Other information related to leases is as follows (in millions of dollars, unless otherwise noted): Eversource CL&P NSTAR Electric PSNH As of December 31, 2019 Weighted-Average Remaining Lease Term (Years): Operating Leases 12 2 20 9 Finance Leases 12 2 22 9 Weighted-Average Discount Rate (Percentage): Operating Leases 3.9 % 2.5 % 4.1 % 3.7 % Finance Leases 4.0 % 10.5 % 2.9 % 3.5 % Eversource CL&P NSTAR Electric PSNH For the Year Ended December 31, 2019 Cash Paid for Amounts Included in the Measurement of Lease Liabilities: Operating Cash Flows from Operating Leases $ 11.4 $ 0.4 $ 1.6 $ 0.1 Operating Cash Flows from Finance Leases 1.2 0.6 0.6 — Financing Cash Flows from Finance Leases 2.6 1.4 — 0.1 Supplemental Non-Cash Information on Lease Liabilities: Right-of-use-Assets Obtained in Exchange for New Operating Lease Liabilities 2.9 1.0 0.1 0.2 Right-of-use-Assets Obtained in Exchange for New Finance Lease Liabilities 2.0 — — — Future minimum lease payments, excluding variable costs, under long-term leases, as of December 31, 2019 are as follows: Operating Leases Finance Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Year Ending December 31, 2020 $ 10.2 $ 0.5 $ 1.8 $ 0.1 $ 3.4 $ 2.0 $ 0.6 $ 0.1 2021 9.0 0.2 1.6 0.1 2.9 1.5 0.6 0.1 2022 7.4 — 1.6 0.1 1.5 — 0.6 0.1 2023 4.9 — 1.6 — 0.8 — 0.6 0.1 2024 2.8 — 1.7 — 0.8 — 0.7 0.1 Thereafter 28.9 0.1 28.7 0.2 13.1 — 12.6 0.5 Future lease payments 63.2 0.8 37.0 0.5 22.5 3.5 15.7 1.0 Less amount representing interest 13.3 0.1 12.8 0.1 12.0 0.5 11.3 0.1 Present value of future minimum lease payments $ 49.9 $ 0.7 $ 24.2 $ 0.4 $ 10.5 $ 3.0 $ 4.4 $ 0.9 At December 31, 2018, future minimum rental payments, excluding executory costs, such as property taxes, state use taxes, insurance, and maintenance were as follows: Operating Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 11.5 $ 1.5 $ 7.2 $ 0.5 2020 9.8 1.4 6.0 0.4 2021 8.7 1.2 5.3 0.4 2022 7.2 1.1 4.4 0.4 2023 4.7 0.5 3.1 0.2 Thereafter 32.7 0.2 29.5 0.3 Future minimum lease payments $ 74.6 $ 5.9 $ 55.5 $ 2.2 Capital Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 3.4 $ 2.0 $ 0.5 $ 0.1 2020 3.4 2.0 0.5 0.1 2021 2.9 1.5 0.5 0.1 2022 1.5 — 0.6 0.1 2023 0.7 — 0.6 0.1 Thereafter 13.9 — 13.4 0.5 Future minimum lease payments 25.8 5.5 16.1 1.0 Less amount representing interest 13.8 1.0 12.4 0.1 Present value of future minimum lease payments $ 12.0 $ 4.5 $ 3.7 $ 0.9

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	12 Months Ended
FAIR VALUE OF FINANCIAL INSTRUMENTS	Dec. 31, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS The following methods and assumptions were used to estimate the fair value of each of the following financial instruments: Preferred Stock, Long-Term Debt and Rate Reduction Bonds: The fair value of CL&P's and NSTAR Electric's preferred stock is based upon pricing models that incorporate interest rates and other market factors, valuations or trades of similar securities and cash flow projections. The fair value of long-term debt and RRB debt securities is based upon pricing models that incorporate quoted market prices for those issues or similar issues adjusted for market conditions, credit ratings of the respective companies and treasury benchmark yields. The fair values provided in the table below are classified as Level 2 within the fair value hierarchy. Carrying amounts and estimated fair values are as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value As of December 31, 2019: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 162.0 $ 116.2 $ 117.8 $ 43.0 $ 44.2 $ — $ — Long-Term Debt 14,098.2 15,170.2 3,518.1 4,058.0 3,342.1 3,659.9 951.6 1,005.7 Rate Reduction Bonds 583.3 625.9 — — — — 583.3 625.9 As of December 31, 2018: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 156.8 $ 116.2 $ 113.8 $ 43.0 $ 43.0 $ — $ — Long-Term Debt 13,086.1 13,154.9 3,254.0 3,429.2 2,944.8 3,024.1 805.2 819.5 Rate Reduction Bonds 635.7 645.8 — — — — 635.7 645.8 Derivative Instruments and Marketable Securities: Derivative instruments and investments in marketable securities are carried at fair value. For further information, see Note 4, "Derivative Instruments," and Note 5, "Marketable Securities," to the financial statements. See Note 1I, "Summary of Significant Accounting Policies – Fair Value Measurements," for the fair value measurement policy and the fair value hierarchy.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)	12 Months Ended
ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)	Dec. 31, 2019
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)	ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) The changes in accumulated other comprehensive income/(loss) by component, net of tax, are as follows: For the Year Ended December 31, 2019 For the Year Ended December 31, 2018 Eversource (Millions of Dollars) Qualified Cash Flow Hedging Instruments Unrealized Defined Benefit Plans Total Qualified Cash Flow Hedging Instruments Unrealized Defined Benefit Plans Total Balance as of January 1st $ (4.4 ) $ (0.5 ) $ (55.1 ) $ (60.0 ) $ (6.2 ) $ — $ (60.2 ) $ (66.4 ) OCI Before Reclassifications — 1.2 (13.3 ) (12.1 ) — (0.5 ) 0.3 (0.2 ) Amounts Reclassified from AOCI 1.4 — 5.6 7.0 1.8 — 4.8 6.6 Net OCI 1.4 1.2 (7.7 ) (5.1 ) 1.8 (0.5 ) 5.1 6.4 Balance as of December 31st $ (3.0 ) $ 0.7 $ (62.8 ) $ (65.1 ) $ (4.4 ) $ (0.5 ) $ (55.1 ) $ (60.0 ) Eversource's qualified cash flow hedging instruments represent interest rate swap agreements on debt issuances that were settled in prior years. The settlement amount was recorded in AOCI and is being amortized into Net Income over the term of the underlying debt instrument. CL&P, NSTAR Electric and PSNH continue to amortize interest rate swaps settled in prior years from AOCI into Interest Expense over the remaining life of the associated long-term debt. Such interest rate swaps are not material to their respective financial statements. Defined benefit plan OCI amounts before reclassifications relate to actuarial gains and losses that arose during the year and were recognized in AOCI. The unamortized actuarial gains and losses and prior service costs on the defined benefit plans are amortized from AOCI into Other Income, Net over the average future employee service period, and are reflected in amounts reclassified from AOCI. The related tax effects recognized in AOCI were net deferred tax assets of $4.4 million and $4.1 million in 2019 and 2017, respectively, and deferred tax liabilities of $0.2 million in 2018. Eversource did not elect to reclassify the income tax effects of the Tax Cuts and Jobs Act from AOCI to Retained Earnings as permitted by ASU 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220). The following table sets forth the amounts reclassified from AOCI by component and the impacted line item on the statements of income: Amounts Reclassified from AOCI Eversource (Millions of Dollars) For the Years Ended December 31, Statements of Income Line Item Impacted 2019 2018 2017 Qualified Cash Flow Hedging Instruments $ (2.5 ) $ (2.8 ) $ (3.3 ) Interest Expense Tax Effect 1.1 1.0 1.3 Income Tax Expense Qualified Cash Flow Hedging Instruments, Net of Tax $ (1.4 ) $ (1.8 ) $ (2.0 ) Defined Benefit Plan Costs: Amortization of Actuarial Losses $ (5.7 ) $ (6.0 ) $ (6.2 ) Other Income, Net (1) Amortization of Prior Service Cost (1.8 ) (0.4 ) (1.1 ) Other Income, Net (1) Total Defined Benefit Plan Costs (7.5 ) (6.4 ) (7.3 ) Tax Effect 1.9 1.6 2.8 Income Tax Expense Defined Benefit Plan Costs, Net of Tax $ (5.6 ) $ (4.8 ) $ (4.5 ) Total Amounts Reclassified from AOCI, Net of Tax $ (7.0 ) $ (6.6 ) $ (6.5 ) (1) These amounts are included in the computation of net periodic Pension, SERP and PBOP costs. See Note 1M, "Summary of Significant Accounting Policies – Other Income, Net" and Note 11A, "Employee Benefits – Pension Benefits and Postretirement Benefits Other Than Pension," for further information. As of December 31, 2019 , it is estimated that a pre-tax amount of $2.5 million ( $0.7 million for NSTAR Electric and $1.8 million for PSNH) will be reclassified from AOCI as a decrease to Net Income over the next 12 months as a result of the amortization of the interest rate swap agreements which have been settled. In addition, it is estimated that a pre-tax amount of $7.8 million will be reclassified from AOCI as a decrease to Net Income over the next 12 months as a result of the amortization of Pension, SERP and PBOP costs.

DIVIDEND RESTRICTIONS

DIVIDEND RESTRICTIONS	12 Months Ended
DIVIDEND RESTRICTIONS	Dec. 31, 2019
Equity [Abstract]
DIVIDEND RESTRICTIONS	DIVIDEND RESTRICTIONS Eversource parent's ability to pay dividends may be affected by certain state statutes, the ability of its subsidiaries to pay common dividends and the leverage restriction tied to its consolidated total debt to total capitalization ratio requirement in its revolving credit agreement. Pursuant to the joint revolving credit agreement of Eversource, CL&P, PSNH, NSTAR Gas, Yankee Gas and Aquarion Water Company of Connecticut, and to the NSTAR Electric revolving credit agreement, each company is required to maintain consolidated total indebtedness to total capitalization ratio of no greater than 65 percent at the end of each fiscal quarter. As of December 31, 2019 , all companies were in compliance with such covenant and in compliance with all such provisions of the revolving credit agreements that may restrict the payment of dividends as of December 31, 2019 . The Retained Earnings balances subject to dividend restrictions were $4.2 billion for Eversource, $1.8 billion for CL&P, $2.3 billion for NSTAR Electric and $490.3 million for PSNH as of December 31, 2019 .

COMMON SHARES

COMMON SHARES	12 Months Ended
COMMON SHARES	Dec. 31, 2019
Equity [Abstract]
COMMON SHARES	COMMON SHARES The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Par Value Authorized as of December 31, 2019 and 2018 Issued as of December 31, 2019 2018 Eversource $ 5 380,000,000 345,858,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301 Common Share Issuance and Forward Sale Agreement: On June 4, 2019, Eversource completed an equity offering of 17,940,000 common shares, consisting of 5,980,000 common shares issued directly by the Company and 11,960,000 common shares issuable pursuant to a forward sale agreement with an investment bank. The issuance of 5,980,000 common shares resulted in proceeds of $426.9 million , net of issuance costs. Under the forward sale agreement, a total of 11,960,000 common shares were borrowed from third parties and sold by the underwriters. The forward sale agreement allows Eversource, at its election and prior to May 29, 2020, to physically settle the forward sale agreement by issuing common shares in exchange for net proceeds at the then-applicable forward sale price specified by the agreement (initially, $71.48 per share) or, alternatively, to settle the forward sale agreement in whole or in part through the delivery or receipt of shares or cash. The forward sale price is subject to adjustment daily based on a floating interest rate factor and will decrease in respect of certain fixed amounts specified in the agreement, such as dividends. On December 30, 2019, Eversource physically settled a portion of the forward sale agreement by delivering 6,000,000 common shares in exchange for net proceeds of $425.4 million . The forward sale price used to determine the cash proceeds received by Eversource was calculated based on the initial forward sale price of $71.48 per share, as adjusted in accordance with the forward sale agreement. The 2019 issuances of 11,980,000 common shares resulted in proceeds of $852.3 million , net of issuance costs, and were reflected in shareholders’ equity and as financing activities on the statement of cash flows. Eversource’s intent is to physically settle the forward sale agreement by issuing common shares. As of December 31, 2019 , if Eversource had elected to net settle the forward sale agreement, Eversource would have been required to pay $84.4 million under a cash settlement or would have been required to deliver 992,189 common shares under a net share settlement. Issuances of shares under the forward sale agreement are classified as equity transactions. Accordingly, no amounts relating to the forward sale agreement have or will be recorded in the financial statements until settlements take place. Prior to any settlements, the only impact to the financial statements is the inclusion of incremental shares within the calculation of diluted EPS using the treasury stock method. See Note 22, "Earnings Per Share," to the financial statements for information on the forward sale agreement’s impact on the calculation of diluted EPS. Eversource used the net proceeds received upon the direct issuance of common shares and the net proceeds received upon partial settlement of the forward sale agreement to repay short-term debt under the commercial paper program, to fund capital spending and clean energy initiatives, and for general corporate purposes. Treasury Shares: As of December 31, 2019 and 2018 , there were 15,977,757 and 16,992,594 Eversource common shares held as treasury shares, respectively. As of December 31, 2019 and 2018 , there were 329,880,645 and 316,885,808 Eversource common shares outstanding, respectively. Beginning in 2019, Eversource began issuing treasury shares to satisfy awards under the Company's incentive plans, shares issued under the dividend reinvestment and share purchase plan, and matching contributions under the Eversource 401k Plan. Dividends on the preferred stock of CL&P and NSTAR Electric totaled $7.5 million for each of the years ended December 31, 2019 , 2018 and 2017 . These dividends were presented as Net Income Attributable to Noncontrolling Interests on the Eversource statements of income. Noncontrolling Interest – Preferred Stock of Subsidiaries on the Eversource balance sheets totaled $155.6 million as of December 31, 2019 and 2018 . On the Eversource balance sheets, Common Shareholders' Equity was fully attributable to Eversource parent and Noncontrolling Interest – Preferred Stock of Subsidiaries was fully attributable to the noncontrolling interest. For the years ended December 31, 2019 , 2018 and 2017 , there was no

PREFERRED STOCK NOT SUBJECT TO

PREFERRED STOCK NOT SUBJECT TO MANDATORY REDEMPTION	12 Months Ended
PREFERRED STOCK NOT SUBJECT TO MANDATORY REDEMPTION	Dec. 31, 2019
Equity [Abstract]
PREFERRED STOCK NOT SUBJECT TO MANDATORY REDEMPTION	PREFERRED STOCK NOT SUBJECT TO MANDATORY REDEMPTION The CL&P and NSTAR Electric preferred stock is not subject to mandatory redemption and is presented as a noncontrolling interest of a subsidiary in Eversource's financial statements. 9,000,000 shares of preferred stock, par value $50 per share, and NSTAR Electric is authorized to issue 2,890,000 shares of preferred stock, par value $100 per share. Holders of preferred stock of CL&P and NSTAR Electric are entitled to receive cumulative dividends in preference to any payment of dividends on the common stock. Upon liquidation, holders of preferred stock of CL&P and NSTAR Electric are entitled to receive a liquidation preference before any distribution to holders of common stock in an amount equal to the par value of the preferred stock plus accrued and unpaid dividends. If the net assets were to be insufficient to pay the liquidation preference in full, then the net assets would be distributed ratably to all holders of preferred stock. The preferred stock of CL&P and NSTAR Electric is subject to optional redemption by the CL&P and NSTAR Electric Boards of Directors at any time. Details of preferred stock not subject to mandatory redemption are as follows (in millions, except in redemption price and shares): Redemption Price Per Share Shares Outstanding as of December 31, As of December 31, Series 2019 2018 2019 2018 CL&P $1.90 Series of 1947 $ 52.50 163,912 163,912 $ 8.2 $ 8.2 $2.00 Series of 1947 $ 54.00 336,088 336,088 16.8 16.8 $2.04 Series of 1949 $ 52.00 100,000 100,000 5.0 5.0 $2.20 Series of 1949 $ 52.50 200,000 200,000 10.0 10.0 3.90% Series of 1949 $ 50.50 160,000 160,000 8.0 8.0 $2.06 Series E of 1954 $ 51.00 200,000 200,000 10.0 10.0 $2.09 Series F of 1955 $ 51.00 100,000 100,000 5.0 5.0 4.50% Series of 1956 $ 50.75 104,000 104,000 5.2 5.2 4.96% Series of 1958 $ 50.50 100,000 100,000 5.0 5.0 4.50% Series of 1963 $ 50.50 160,000 160,000 8.0 8.0 5.28% Series of 1967 $ 51.43 200,000 200,000 10.0 10.0 $3.24 Series G of 1968 $ 51.84 300,000 300,000 15.0 15.0 6.56% Series of 1968 $ 51.44 200,000 200,000 10.0 10.0 Total CL&P 2,324,000 2,324,000 $ 116.2 $ 116.2 NSTAR Electric 4.25% Series of 1956 $ 103.625 180,000 180,000 $ 18.0 $ 18.0 4.78% Series of 1958 $ 102.80 250,000 250,000 25.0 25.0 Total NSTAR Electric 430,000 430,000 $ 43.0 $ 43.0 Fair Value Adjustment due to Merger with NSTAR (3.6 ) (3.6 ) Other 6.00% Series of 1958 $ 100.00 23 23 $ — $ — Total Eversource - Noncontrolling Interest - Preferred Stock of Subsidiaries $ 155.6 $ 155.6

COMMON SHAREHOLDERS' EQUITY AND

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	12 Months Ended
COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	Dec. 31, 2019
Equity [Abstract]
COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	COMMON SHARES The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Par Value Authorized as of December 31, 2019 and 2018 Issued as of December 31, 2019 2018 Eversource $ 5 380,000,000 345,858,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301 Common Share Issuance and Forward Sale Agreement: On June 4, 2019, Eversource completed an equity offering of 17,940,000 common shares, consisting of 5,980,000 common shares issued directly by the Company and 11,960,000 common shares issuable pursuant to a forward sale agreement with an investment bank. The issuance of 5,980,000 common shares resulted in proceeds of $426.9 million , net of issuance costs. Under the forward sale agreement, a total of 11,960,000 common shares were borrowed from third parties and sold by the underwriters. The forward sale agreement allows Eversource, at its election and prior to May 29, 2020, to physically settle the forward sale agreement by issuing common shares in exchange for net proceeds at the then-applicable forward sale price specified by the agreement (initially, $71.48 per share) or, alternatively, to settle the forward sale agreement in whole or in part through the delivery or receipt of shares or cash. The forward sale price is subject to adjustment daily based on a floating interest rate factor and will decrease in respect of certain fixed amounts specified in the agreement, such as dividends. On December 30, 2019, Eversource physically settled a portion of the forward sale agreement by delivering 6,000,000 common shares in exchange for net proceeds of $425.4 million . The forward sale price used to determine the cash proceeds received by Eversource was calculated based on the initial forward sale price of $71.48 per share, as adjusted in accordance with the forward sale agreement. The 2019 issuances of 11,980,000 common shares resulted in proceeds of $852.3 million , net of issuance costs, and were reflected in shareholders’ equity and as financing activities on the statement of cash flows. Eversource’s intent is to physically settle the forward sale agreement by issuing common shares. As of December 31, 2019 , if Eversource had elected to net settle the forward sale agreement, Eversource would have been required to pay $84.4 million under a cash settlement or would have been required to deliver 992,189 common shares under a net share settlement. Issuances of shares under the forward sale agreement are classified as equity transactions. Accordingly, no amounts relating to the forward sale agreement have or will be recorded in the financial statements until settlements take place. Prior to any settlements, the only impact to the financial statements is the inclusion of incremental shares within the calculation of diluted EPS using the treasury stock method. See Note 22, "Earnings Per Share," to the financial statements for information on the forward sale agreement’s impact on the calculation of diluted EPS. Eversource used the net proceeds received upon the direct issuance of common shares and the net proceeds received upon partial settlement of the forward sale agreement to repay short-term debt under the commercial paper program, to fund capital spending and clean energy initiatives, and for general corporate purposes. Treasury Shares: As of December 31, 2019 and 2018 , there were 15,977,757 and 16,992,594 Eversource common shares held as treasury shares, respectively. As of December 31, 2019 and 2018 , there were 329,880,645 and 316,885,808 Eversource common shares outstanding, respectively. Beginning in 2019, Eversource began issuing treasury shares to satisfy awards under the Company's incentive plans, shares issued under the dividend reinvestment and share purchase plan, and matching contributions under the Eversource 401k Plan. Dividends on the preferred stock of CL&P and NSTAR Electric totaled $7.5 million for each of the years ended December 31, 2019 , 2018 and 2017 . These dividends were presented as Net Income Attributable to Noncontrolling Interests on the Eversource statements of income. Noncontrolling Interest – Preferred Stock of Subsidiaries on the Eversource balance sheets totaled $155.6 million as of December 31, 2019 and 2018 . On the Eversource balance sheets, Common Shareholders' Equity was fully attributable to Eversource parent and Noncontrolling Interest – Preferred Stock of Subsidiaries was fully attributable to the noncontrolling interest. For the years ended December 31, 2019 , 2018 and 2017 , there was no

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
EARNINGS PER SHARE	Dec. 31, 2019
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic EPS is computed based upon the weighted average number of common shares outstanding during each period. Diluted EPS is computed on the basis of the weighted average number of common shares outstanding plus the potential dilutive effect of certain share-based compensation awards and the equity forward sale agreement, as if they were converted into outstanding common shares. The dilutive effect of unvested RSU and performance share awards, as well as the equity forward sale agreement, is calculated using the treasury stock method. RSU and performance share awards are included in basic weighted average common shares outstanding as of the date that all necessary vesting conditions have been satisfied. As described in Note 19, "Common Shares," earnings per share dilution, if any, related to the forward sale agreement will be determined under the treasury stock method until settlement of the forward sale agreement. Under this method, the number of Eversource common shares used in calculating diluted EPS is deemed to be increased by the excess, if any, of the number of shares that would be issued upon physical settlement of the forward sale agreement less the number of shares that would be purchased by Eversource in the market (based on the average market price during the same reporting period) using the proceeds receivable upon settlement (based on the adjusted forward sale price at the end of that reporting period). Share dilution occurs when the average market price of Eversource's common shares is higher than the adjusted forward sale price. The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Years Ended December 31, 2019 2018 2017 Net Income Attributable to Common Shareholders $ 909.1 $ 1,033.0 $ 988.0 Weighted Average Common Shares Outstanding: Basic 321,416,086 317,370,369 317,411,097 Dilutive Effect of: Share-Based Compensation Awards and Other 762,215 623,565 620,483 Equity Forward Sale Agreement 763,335 — — Total Dilutive Effect 1,525,550 623,565 620,483 Diluted 322,941,636 317,993,934 318,031,580 Basic EPS $ 2.83 $ 3.25 $ 3.11 Diluted EPS $ 2.81 $ 3.25 $ 3.11

REVENUES

REVENUES	12 Months Ended
REVENUES	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUES On January 1, 2018, Eversource, including CL&P, NSTAR Electric and PSNH, adopted ASU 2014-09, “ Revenue from Contracts with Customers (Topic 606) ” using the modified retrospective approach. The core principle of this accounting guidance is that revenue is recognized when promised goods or services (referred to as performance obligations) are transferred to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. A five-step model is used for recognizing and measuring revenue from contracts with customers, which includes identifying the contract with the customer, identifying the performance obligations promised within the contract, determining the transaction price (the amount of consideration to which the company expects to be entitled), allocating the transaction price to the performance obligations and recognizing revenue when (or as) the performance obligation is satisfied. The following table presents operating revenues disaggregated by revenue source: For the Year Ended December 31, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 3,723.7 $ 555.1 $ — $ 132.3 $ — $ — $ 4,411.1 Commercial 2,584.8 347.6 — 63.9 — (4.3 ) 2,992.0 Industrial 331.8 96.9 — 4.5 — (11.6 ) 421.6 Total Retail Tariff Sales Revenues 6,640.3 999.6 — 200.7 — (15.9 ) 7,824.7 Wholesale Transmission Revenues — — 1,293.3 — 61.3 (1,085.2 ) 269.4 Wholesale Market Sales Revenues 215.7 55.4 — 4.1 — — 275.2 Other Revenues from Contracts with Customers 54.8 2.8 13.2 7.0 967.2 (969.0 ) 76.0 Reserve for Revenues Subject to Refund 1.3 6.2 — (2.8 ) — — 4.7 Total Revenues from Contracts with Customers 6,912.1 1,064.0 1,306.5 209.0 1,028.5 (2,070.1 ) 8,450.0 Alternative Revenue Programs 45.9 (4.9 ) 81.8 4.6 — (74.2 ) 53.2 Other Revenues 18.5 3.1 0.7 1.0 — — 23.3 Total Operating Revenues $ 6,976.5 $ 1,062.2 $ 1,389.0 $ 214.6 $ 1,028.5 $ (2,144.3 ) $ 8,526.5 For the Year Ended December 31, 2018 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 3,766.6 $ 542.5 $ — $ 130.7 $ — $ — $ 4,439.8 Commercial 2,634.7 334.8 — 63.3 — (4.5 ) 3,028.3 Industrial 351.9 96.0 — 4.4 — (10.0 ) 442.3 Total Retail Tariff Sales Revenues 6,753.2 973.3 — 198.4 — (14.5 ) 7,910.4 Wholesale Transmission Revenues — — 1,308.9 — 47.3 (1,092.2 ) 264.0 Wholesale Market Sales Revenues 179.5 57.5 — 4.1 — — 241.1 Other Revenues from Contracts with Customers 65.9 (2.2 ) 12.6 7.2 889.0 (891.0 ) 81.5 Reserve for Revenues Subject to Refund (12.3 ) (8.3 ) — (3.7 ) — — (24.3 ) Total Revenues from Contracts with Customers 6,986.3 1,020.3 1,321.5 206.0 936.3 (1,997.7 ) 8,472.7 Alternative Revenue Programs (47.0 ) (1.2 ) (35.2 ) 5.4 — 31.9 (46.1 ) Other Revenues 17.9 3.1 — 0.6 — — 21.6 Total Operating Revenues $ 6,957.2 $ 1,022.2 $ 1,286.3 $ 212.0 $ 936.3 $ (1,965.8 ) $ 8,448.2 For the Years Ended December 31, 2019 2018 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,837.1 $ 1,322.1 $ 564.5 $ 1,828.2 $ 1,380.9 $ 557.5 Commercial 922.9 1,349.4 314.6 928.1 1,391.5 316.9 Industrial 138.3 115.8 77.7 147.7 124.9 79.3 Total Retail Tariff Sales Revenues 2,898.3 2,787.3 956.8 2,904.0 2,897.3 953.7 Wholesale Transmission Revenues 587.1 517.3 188.9 620.6 488.8 199.5 Wholesale Market Sales Revenues 105.1 73.1 37.5 48.3 76.1 56.6 Other Revenues from Contracts with Customers 36.4 18.7 15.6 35.0 28.9 15.5 Reserve for Revenues Subject to Refund — — 1.3 — — (12.3 ) Total Revenues from Contracts with Customers 3,626.9 3,396.4 1,200.1 3,607.9 3,491.1 1,213.0 Alternative Revenue Programs 77.5 41.6 8.6 (65.9 ) 0.9 (17.3 ) Other Revenues 10.3 7.0 1.9 8.5 8.3 1.1 Eliminations (482.1 ) (400.4 ) (144.7 ) (454.3 ) (387.4 ) (149.2 ) Total Operating Revenues $ 3,232.6 $ 3,044.6 $ 1,065.9 $ 3,096.2 $ 3,112.9 $ 1,047.6 Retail Tariff Sales: Regulated utilities provide products and services to their regulated customers under rates, pricing, payment terms and conditions of service, regulated by each state regulatory agency. The arrangement whereby a utility provides commodity service to a customer for a price approved by the respective state regulatory commission is referred to as a tariff sale contract, and the tariff governs all aspects of the provision of regulated services by utilities. The majority of revenue for Eversource, CL&P, NSTAR Electric and PSNH is derived from regulated retail tariff sales for the sale and distribution of electricity, natural gas and water to residential, commercial and industrial retail customers. The utility's performance obligation for the regulated tariff sales is to provide electricity, natural gas or water to the customer as demanded. The promise to provide the commodity represents a single performance obligation, as it is a promise to transfer a series of distinct goods or services that are substantially the same and that have the same pattern of transfer to the customer. Revenue is recognized over time as the customer simultaneously receives and consumes the benefits provided by the utility, and the utility satisfies its performance obligation. Revenue is recognized based on the output method as there is a directly observable output to the customer (electricity, natural gas or water units delivered to the customer and immediately consumed). Each Eversource utility is entitled to be compensated for performance completed to date (service taken by the customer) until service is terminated. In regulated tariff sales, the transaction prices are the rates approved by the respective state regulatory commissions. In general, rates can only be changed through formal proceedings with the state regulatory commissions. These rates are designed to recover the costs to provide service to customers and include a return on investment. Regulatory commission-approved tracking mechanisms are included in these rates and are also used to recover, on a fully-reconciling basis, certain costs, such as the procurement of energy supply, retail transmission charges, energy efficiency program costs, net metering for distributed generation, and restructuring and stranded costs. These tracking mechanisms result in rates being changed periodically to ensure recovery of actual costs incurred. Customers may elect to purchase electricity from each Eversource electric utility or may contract separately with a competitive third party supplier. Revenue is not recorded for the sale of the electricity commodity to customers who have contracted separately with these suppliers, only the delivery to a customer, as the utility is acting as an agent on behalf of the third party supplier. Wholesale Transmission Revenues: The Eversource electric transmission-owning companies (CL&P, NSTAR Electric and PSNH) each own and maintain transmission facilities that are part of an interstate power transmission grid over which electricity is transmitted throughout New England. CL&P, NSTAR Electric and PSNH, as well as most other New England utilities, are parties to a series of agreements that provide for coordinated planning and operation of the region's transmission facilities and the rules by which they acquire transmission services. The Eversource electric transmission-owning companies have a combination of FERC-approved regional and local formula rates that work in tandem to recover all their transmission costs. These rates are part of the ISO-NE Tariff. Regional rates recover the costs of higher voltage transmission facilities that benefit the region and are collected from all New England transmission customers, including the Eversource distribution businesses. Eversource's local rates recover the companies' total transmission revenue requirements, less revenues received from regional rates and other sources, and are collected from Eversource's distribution businesses and other transmission customers. The distribution businesses of Eversource, in turn, recover the FERC approved charges from retail customers through annual or semiannual tracking mechanisms, which are retail tariff sales. The utility's performance obligation for regulated wholesale transmission sales is to provide transmission services to the customer as demanded. The promise to provide transmission service represents a single performance obligation. The transaction prices are the transmission rate formulas as defined by the ISO-NE Tariff and are regulated and established by FERC. Wholesale transmission revenue is recognized over time as the performance obligation is completed, which occurs as transmission services are provided to customers. The revenue is recognized based on the output method. Each Eversource utility is entitled to be compensated for performance completed to date (e.g., use of the transmission system by the customer). Wholesale Market Sales Revenues: Wholesale market sales transactions include sales of energy and energy-related products into the ISO-NE wholesale electricity market, sales of natural gas to third party marketers, and also the sale of RECs to various counterparties. ISO-NE oversees the region's wholesale electricity market and administers the transactions and terms and conditions, including payment terms, which are established in the ISO-NE tariff, between the buyers and sellers in the market. Pricing is set by the wholesale market. The wholesale transactions in the ISO-NE market occur on a day-ahead basis or a real-time basis (daily) and are, therefore, short-term. Transactions are tracked and reported by ISO-NE net by the hour, which is the net hourly position of energy sales and purchases by each market participant. Beginning in the first quarter of 2018, the performance obligation for ISO-NE energy transactions is defined to be the net by hour transaction. Revenue is recognized when the performance obligation for these energy sales transactions is satisfied, when the sale occurs and the energy is transferred to the customer. For sales of natural gas, transportation, and natural gas pipeline capacity to third party marketers, revenue is recognized when the performance obligation is satisfied at the point in time the sale occurs and the natural gas or related product is transferred to the marketer. RECs are sold to various counterparties, and revenue is recognized when the performance obligation is satisfied upon transfer of title to the customer through the New England Power Pool Generation Information System. Other Revenues from Contracts with Customers: Other revenues from contracts with customers primarily include property rentals that are not deemed leases. These revenues are generally recognized on a straight-line basis over time as the service is provided to the customer. Other revenues also include revenues from Eversource's service company, which is eliminated in consolidation. Reserve for Revenues Subject to Refund: Current base rates include an estimate of income taxes, which was based on the U.S. federal corporate income tax rate in effect at the time of the rate proceeding. Eversource established a regulatory liability, recorded as a reduction to revenue, to reflect the difference between the 35 percent federal corporate income tax rate included in rates charged to customers and the 21 percent federal corporate income tax rate, effective January 1, 2018 as a result of the Tax Cuts and Jobs Act, until rates billed to customers reflect the lower federal tax rate. Effective May 1, 2018, CL&P adjusted distribution rates billed to customers to reflect the lower federal income tax rate prospectively and, as of December 31, 2018, fully refunded its regulatory liability associated with the higher federal corporate income tax rate billed to customers in the period between January 1, 2018 through April 30, 2018. Effective November 15, 2018, Yankee Gas adjusted distribution rates to reflect the lower federal income tax rate prospectively and to refund its regulatory liability associated with the higher federal corporate income tax rate billed to customers in the period between January 1, 2018 through November 14, 2018. Effective July 1, 2019, PSNH adjusted temporary distribution rates to reflect the lower federal income tax rate prospectively and to refund its regulatory liability associated with the higher federal corporate income tax rate billed to customers in the period between January 1, 2018 through June 30, 2019. For NSTAR Electric and NSTAR Gas, a December 2018 DPU order indicated that the DPU would not require a revision to base distribution rates for any potential refunds associated with the higher federal corporate income tax rate billed to customers in the period between January 1, 2018 to the effective dates of each company's rate changes (effective February 1, 2018 for NSTAR Electric and July 1, 2018 for NSTAR Gas). Alternative Revenue Programs: In accordance with accounting guidance for rate-regulated operations, certain of Eversource's utilities' rate making mechanisms qualify as alternative revenue programs (ARPs) if they meet specified criteria, in which case revenues may be recognized prior to billing based on allowed levels of collection in rates. Eversource's utility companies recognize revenue and record a regulatory asset or liability once the condition or event allowing for the automatic adjustment of future rates occurs. ARP revenues include both the recognition of the deferral adjustment to ARP revenues, when the regulator-specified condition or event allowing for additional billing or refund has occurred, and an equal and offsetting reversal of the ARP deferral to revenues as those amounts are reflected in the price of service in subsequent periods. Eversource’s ARPs include the revenue decoupling mechanism and the annual reconciliation adjustment to transmission formula rates, described below. • Certain Eversource electric, natural gas and water companies, including CL&P and NSTAR Electric, have revenue decoupling mechanisms approved by a regulatory commission (decoupled companies). Decoupled companies’ distribution revenues are not directly based on sales volumes. The decoupled companies reconcile their annual base distribution rate recovery to pre-established levels of baseline distribution delivery service revenues, with any difference between the allowed level of distribution revenue and the actual amount realized adjusted through subsequent rates. • The transmission formula rates provide for the annual reconciliation and recovery or refund of estimated costs to actual costs. The financial impacts of differences between actual and estimated costs are deferred for future recovery from, or refund to, transmission customers. This transmission deferral reconciles billed transmission revenues to the revenue requirement for our transmission businesses. Other Revenues: Other Revenues include certain fees charged to customers that are not considered revenue from contracts with customers and lease revenues under lessor accounting guidance. Lease revenues totaled $4.4 million at Eversource, $1.0 million at CL&P, and $2.7 million at NSTAR Electric for the year ended December 31, 2019. Intercompany Eliminations: Intercompany eliminations are primarily related to the Eversource electric transmission revenues that are derived from ISO-NE regional transmission charges to the distribution businesses of CL&P, NSTAR Electric and PSNH that recover the costs of the wholesale transmission business, and revenues from Eversource's service company. Intercompany revenues and expenses between the Eversource wholesale transmission businesses and the Eversource distribution businesses and from Eversource's service company are eliminated in consolidation and included in "Eliminations" in the table above. Receivables: Receivables, Net on the balance sheet include trade receivables from our retail customers and receivables arising from ISO-NE billing related to wholesale transmission contracts and wholesale market transactions, sales of natural gas and capacity to marketers, sales of RECs, and property rentals. In general, retail tariff customers and wholesale transmission customers are billed monthly and the payment terms are generally due and payable upon receipt of the bill. Unbilled Revenues: Unbilled Revenues on the balance sheet represent estimated amounts due from retail customers for electricity, natural gas or water delivered to customers but not yet billed. The utility company has satisfied its performance obligation and the customer has received and consumed the commodity as of the balance sheet date, and therefore, the utility company records revenue for those services in the period the services were provided. Only the passage of time is required before the company is entitled to payment for the satisfaction of the performance obligation. Payment from customers is due monthly as services are rendered and amounts are billed. Actual amounts billed to customers when meter readings become available may vary from the estimated amount. Unbilled revenues are recognized by allocating estimated unbilled sales volumes to the respective customer classes, and then applying an estimated rate by customer class to those sales volumes. Unbilled revenue estimates reflect seasonality, weather, customer usage patterns, customer rates in effect for customer classes, and the timing of customer billing. The companies that have a decoupling mechanism record a regulatory deferral to reflect the actual allowed amount of revenue associated with their respective decoupled distribution rate design. Practical Expedients:

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
SEGMENT INFORMATION	Dec. 31, 2019
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION Eversource is organized into the Electric Distribution, Electric Transmission, Natural Gas Distribution and Water Distribution reportable segments and Other based on a combination of factors, including the characteristics of each segments' services, the sources of operating revenues and expenses and the regulatory environment in which each segment operates. These reportable segments represent substantially all of Eversource's total consolidated revenues. Revenues from the sale of electricity, natural gas and water primarily are derived from residential, commercial and industrial customers and are not dependent on any single customer. The Electric Distribution reportable segment includes the results of PSNH's generation facilities prior to sales in January and August 2018, and NSTAR Electric's solar power facilities. On December 4, 2017, Eversource acquired Aquarion, and its water distribution business was deemed a reportable segment beginning in 2018. Eversource's reportable segments are determined based upon the level at which Eversource's chief operating decision maker assesses performance and makes decisions about the allocation of company resources. The remainder of Eversource's operations is presented as Other in the tables below and primarily consists of 1) the equity in earnings of Eversource parent from its subsidiaries and intercompany interest income, both of which are eliminated in consolidation, and interest expense related to the debt of Eversource parent, 2) the revenues and expenses of Eversource Service, most of which are eliminated in consolidation, 3) the operations of CYAPC and YAEC, 4) Eversource Water Ventures, Inc., parent company of Aquarion, 5) the results of other unregulated subsidiaries, which are not part of its core business, and 6) Eversource parent's equity ownership interests that are not consolidated, which primarily include the offshore wind business, a natural gas pipeline owned by Enbridge, Inc., and a renewable energy investment fund. In the ordinary course of business, Yankee Gas and NSTAR Gas purchase natural gas transmission services from the Enbridge, Inc. natural gas pipeline project described above. These affiliate transaction costs total $62.5 million annually and are classified as Purchased Power, Fuel and Transmission on the Eversource statements of income. Each of Eversource's subsidiaries, including CL&P, NSTAR Electric and PSNH, has one reportable segment. Cash flows used for investments in plant included in the segment information below are cash capital expenditures that do not include amounts incurred but not paid, cost of removal, AFUDC related to equity funds, and the capitalized portions of pension and PBOP expense. Eversource's segment information is as follows: For the Year Ended December 31, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 6,976.5 $ 1,062.2 $ 1,389.0 $ 214.6 $ 1,028.5 $ (2,144.3 ) $ 8,526.5 Depreciation and Amortization (651.3 ) (68.3 ) (253.3 ) (46.9 ) (63.2 ) 2.3 (1,080.7 ) Impairment of Northern Pass Transmission — — (239.6 ) — — — (239.6 ) Other Operating Expenses (5,525.1 ) (830.8 ) (411.2 ) (101.0 ) (891.3 ) 2,143.7 (5,615.7 ) Operating Income 800.1 163.1 484.9 66.7 74.0 1.7 1,590.5 Interest Expense (206.4 ) (47.4 ) (125.7 ) (34.6 ) (170.3 ) 51.2 (533.2 ) Interest Income 13.3 0.1 1.5 — 48.7 (50.8 ) 12.8 Other Income, Net 46.8 1.6 29.2 0.4 1,041.5 (999.5 ) 120.0 Income Tax (Expense)/Benefit (135.9 ) (21.2 ) (130.5 ) 2.4 11.7 — (273.5 ) Net Income 517.9 96.2 259.4 34.9 1,005.6 (997.4 ) 916.6 Net Income Attributable to Noncontrolling Interests (4.6 ) — (2.9 ) — — — (7.5 ) Net Income Attributable to Common Shareholders $ 513.3 $ 96.2 $ 256.5 $ 34.9 $ 1,005.6 $ (997.4 ) $ 909.1 Total Assets (as of) $ 22,541.9 $ 4,345.5 $ 10,904.0 $ 2,351.7 $ 20,469.6 $ (19,488.8 ) $ 41,123.9 Cash Flows Used for Investments in Plant $ 1,104.2 $ 460.2 $ 987.0 $ 118.0 $ 242.1 $ — $ 2,911.5 For the Year Ended December 31, 2018 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues (1) $ 6,957.2 $ 1,022.2 $ 1,286.3 $ 212.0 $ 936.3 $ (1,965.8 ) $ 8,448.2 Depreciation and Amortization (671.8 ) (75.0 ) (231.8 ) (46.5 ) (49.1 ) 2.2 (1,072.0 ) Other Operating Expenses (1) (5,548.6 ) (787.6 ) (375.5 ) (99.8 ) (831.5 ) 1,966.7 (5,676.3 ) Operating Income 736.8 159.6 679.0 65.7 55.7 3.1 1,699.9 Interest Expense (202.8 ) (44.1 ) (120.6 ) (34.3 ) (129.3 ) 32.3 (498.8 ) Interest Income 18.7 — 2.4 — 30.3 (33.3 ) 18.1 Other Income/(Loss), Net 67.5 7.1 31.1 (0.4 ) 1,185.3 (1,180.3 ) 110.3 Income Tax (Expense)/Benefit (160.2 ) (29.4 ) (161.8 ) (0.1 ) 62.5 — (289.0 ) Net Income 460.0 93.2 430.1 30.9 1,204.5 (1,178.2 ) 1,040.5 Net Income Attributable to Noncontrolling Interests (4.6 ) — (2.9 ) — — — (7.5 ) Net Income Attributable to Common Shareholders $ 455.4 $ 93.2 $ 427.2 $ 30.9 $ 1,204.5 $ (1,178.2 ) $ 1,033.0 Total Assets (as of) $ 21,389.1 $ 3,904.9 $ 10,285.0 $ 2,253.0 $ 17,874.2 $ (17,464.9 ) $ 38,241.3 Cash Flows Used for Investments in Plant (2) $ 961.3 $ 351.5 $ 976.2 $ 102.3 $ 178.6 $ — $ 2,569.9 For the Year Ended December 31, 2017 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Operating Revenues (1) $ 5,542.9 $ 947.3 $ 1,301.7 $ 15.9 $ 931.0 $ (986.8 ) $ 7,752.0 Depreciation and Amortization (542.6 ) (72.9 ) (209.4 ) (3.7 ) (37.4 ) 2.2 (863.8 ) Other Operating Expenses (1) (4,072.6 ) (716.4 ) (382.8 ) (8.3 ) (806.6 ) 986.7 (5,000.0 ) Operating Income 927.7 158.0 709.5 3.9 87.0 2.1 1,888.2 Interest Expense (186.3 ) (43.1 ) (115.1 ) (3.1 ) (90.0 ) 15.8 (421.8 ) Interest Income 7.3 0.1 1.8 0.1 15.7 (16.7 ) 8.3 Other Income, Net 41.6 3.8 27.3 — 1,113.0 (1,086.0 ) 99.7 Income Tax Expense (288.3 ) (44.2 ) (228.7 ) (2.1 ) (15.5 ) (0.1 ) (578.9 ) Net Income/(Loss) 502.0 74.6 394.8 (1.2 ) 1,110.2 (1,084.9 ) 995.5 Net Income Attributable to Noncontrolling Interests (4.6 ) — (2.9 ) — — — (7.5 ) Net Income/(Loss) Attributable to Common $ 497.4 $ 74.6 $ 391.9 $ (1.2 ) $ 1,110.2 $ (1,084.9 ) $ 988.0 Cash Flows Used for Investments in Plant $ 1,020.7 $ 298.2 $ 867.6 $ 16.0 $ 145.6 $ — $ 2,348.1 (1) Effective January 1, 2018, upon implementation of the new revenue accounting guidance, the electric distribution segment is presented gross and intercompany transmission billings are presented in the eliminations column, as Eversource believes that the electric distribution segment acts as a principal, rather than an agent, in its contracts with retail customers. Retail customers contract directly with the electric distribution utility and do not differentiate between distribution and transmission services. Therefore, the electric distribution segment revenues, which are derived from retail customer billings, are presented gross of the eliminations. Prior to 2018, the electric distribution segment presented intercompany electric transmission billings net, based on indicators of net presentation prior to the new revenue guidance. See Note 23 "Revenues," to the financial statements regarding accounting for revenues. (2) See Note 1B, "Summary of Significant Accounting Policies - Basis of Presentation," for information regarding the correction of cash investments in plant reported in 2018.

ACQUISITION OF AQUARION AND GOO

ACQUISITION OF AQUARION AND GOODWILL	12 Months Ended
ACQUISITION OF AQUARION AND GOODWILL	Dec. 31, 2019
Business Combinations [Abstract]
ACQUISITION OF AQUARION AND GOODWILL	ACQUISITION OF AQUARION AND GOODWILL A. Acquisition of Aquarion On December 4, 2017, Eversource acquired Aquarion for a purchase price of $1.675 billion , consisting of approximately $880 million in cash and $795 million of assumed Aquarion debt. Aquarion is a holding company that owns three separate regulated water utility subsidiaries engaged in the water collection, treatment and distribution business that operate in Connecticut, Massachusetts and New Hampshire. These regulated utilities collect, treat and distribute water to residential, commercial and industrial customers, to other utilities for resale, and for private and municipal fire protection. Aquarion and its subsidiaries became wholly-owned subsidiaries of Eversource, and Eversource's consolidated financial information includes Aquarion and its subsidiaries' activity beginning December 4, 2017. The approximate $880 million cash purchase price included the $745 million equity purchase price plus a $135 million shareholder loan that was repaid at closing. Pro Forma Financial Information: The following unaudited pro forma financial information reflects the pro forma combined results of operations of Eversource and Aquarion and reflects the amortization of purchase price adjustments assuming the acquisition had taken place on January 1, 2017. The unaudited pro forma financial information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Eversource. (Pro forma amounts in millions, except share amounts) For the Year Ended December 31, 2017 Operating Revenues $ 7,947.7 Net Income Attributable to Common Shareholders 1,019.1 Basic EPS 3.21 Diluted EPS 3.20 Aquarion Revenues and Pre-Tax Income: The impact of Aquarion on Eversource's accompanying consolidated statement of income included operating revenues of $15.9 million and pre-tax income of $1.1 million for the year ended December 31, 2017. B. Goodwill In a business combination, the excess of the purchase price over the estimated fair values of the assets acquired and liabilities assumed is recognized as goodwill. Goodwill is evaluated for impairment at least annually and more frequently if indicators of impairment arise. In accordance with the accounting standards, if the fair value of a reporting unit is less than its carrying value (including goodwill), the goodwill is tested for impairment. Goodwill is not subject to amortization, however is subject to a fair value based assessment for impairment at least annually and whenever facts or circumstances indicate that there may be an impairment. A resulting write-down, if any, would be charged to Operating Expenses. Eversource's reporting units for the purpose of testing goodwill are Electric Distribution, Electric Transmission, Natural Gas Distribution and Water Distribution. These reporting units are consistent with the operating segments underlying the reportable segments identified in Note 24, "Segment Information," to the financial statements. Eversource completed its annual goodwill impairment test for Electric Distribution, Electric Transmission, Natural Gas Distribution and Water Distribution reporting units as of October 1, 2019 and determined that no impairment existed. There were no events subsequent to October 1, 2019 that indicated impairment of goodwill. The annual goodwill assessment included an evaluation of the Company's share price and credit ratings, analyst reports, financial performance, cost and risk factors, long-term strategy, growth and future projections, as well as macroeconomic, industry and market conditions. This evaluation required the consideration of several factors that impact the fair value of the reporting units, including conditions and assumptions that affect the future cash flows of the reporting units. Key considerations include discount rates, utility sector market performance and merger transaction multiples, and internal estimates of future cash flows and net income. The following table presents goodwill by reportable segment as of December 31, 2019 and 2018 : (Billions of Dollars) Electric Distribution Electric Transmission Natural Gas Distribution Water Distribution Total Goodwill $ 2.5 $ 0.6 $ 0.4 $ 0.9 $ 4.4

QUARTERLY FINANCIAL DATA (UNAUD

QUARTERLY FINANCIAL DATA (UNAUDITED)	12 Months Ended
QUARTERLY FINANCIAL DATA (UNAUDITED)	Dec. 31, 2019
Quarterly Financial Data [Abstract]
QUARTERLY FINANCIAL DATA (UNAUDITED)	QUARTERLY FINANCIAL DATA (UNAUDITED) Quarter Ended Eversource (Millions of Dollars, except per share information) 2019 2018 March 31, June 30, (2) September 30, December 31, March 31, June 30, September 30, December 31, Operating Revenues $ 2,415.8 $ 1,884.5 $ 2,175.8 $ 2,050.4 $ 2,288.0 $ 1,853.9 $ 2,271.4 $ 2,034.9 Operating Income 494.7 151.0 509.2 435.6 442.5 391.4 466.0 400.0 Net Income 310.6 33.3 320.8 251.9 271.4 244.6 291.3 233.2 Net Income Attributable to Common Shareholders 308.7 31.5 318.9 250.0 269.5 242.8 289.4 231.3 Basic EPS (1) $ 0.97 $ 0.10 $ 0.98 $ 0.77 $ 0.85 $ 0.76 $ 0.91 $ 0.73 Diluted EPS (1) $ 0.97 $ 0.10 $ 0.98 $ 0.76 $ 0.85 $ 0.76 $ 0.91 $ 0.73 (1) The summation of quarterly EPS data may not equal annual data due to rounding. (2) In the second quarter of 2019, Eversource recorded an impairment charge related to NPT of $239.6 million within Operating Income on the statement of income. For further information, see Note 1D, "Summary of Significant Accounting Policies - Impairment of Northern Pass Transmission," to the financial statements. Quarter Ended 2019 2018 (Millions of Dollars) March 31, June 30, September 30, December 31, March 31, June 30, September 30, December 31, CL&P Operating Revenues $ 849.2 $ 740.8 $ 853.9 $ 788.7 $ 785.0 $ 694.9 $ 865.0 $ 751.3 Operating Income 171.8 166.8 190.3 152.7 157.2 163.1 172.7 142.8 Net Income 110.5 104.8 111.7 83.9 98.6 99.7 100.3 79.1 NSTAR Electric Operating Revenues $ 797.6 $ 681.9 $ 878.7 $ 686.4 $ 770.1 $ 690.7 $ 939.5 $ 712.6 Operating Income 137.8 134.2 219.4 135.5 119.0 133.6 205.5 126.0 Net Income 94.0 89.7 154.9 93.4 77.1 87.9 140.6 77.5 PSNH Operating Revenues $ 276.4 $ 240.9 $ 280.4 $ 268.2 $ 267.4 $ 235.1 $ 290.2 $ 254.9 Operating Income 49.7 46.3 64.5 56.0 55.8 46.9 56.5 37.2 Net Income 32.8 26.9 40.9 33.4 35.1 25.8 40.7 14.3

SCHEDULE I - FINANCIAL INFORMAT

SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT	12 Months Ended
SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT	SCHEDULE I EVERSOURCE ENERGY (PARENT) FINANCIAL INFORMATION OF REGISTRANT BALANCE SHEETS AS OF DECEMBER 31, 2019 AND 2018 (Thousands of Dollars) 2019 2018 ASSETS Current Assets: Cash $ 1,469 $ 591 Accounts Receivable from Subsidiaries 25,070 32,175 Notes Receivable from Subsidiaries 1,376,000 991,400 Prepayments and Other Current Assets 33,546 26,861 Total Current Assets 1,436,085 1,051,027 Deferred Debits and Other Assets: Investments in Subsidiary Companies, at Equity 13,162,337 12,009,659 Notes Receivable from Subsidiaries 157,000 323,500 Accumulated Deferred Income Taxes 27,578 40,454 Goodwill 3,231,811 3,231,811 Other Long-Term Assets 92,394 73,669 Total Deferred Debits and Other Assets 16,671,120 15,679,093 Total Assets $ 18,107,205 $ 16,730,120 LIABILITIES AND CAPITALIZATION Current Liabilities: Notes Payable $ 878,584 $ 631,500 Long-Term Debt - Current Portion 23,933 378,883 Accounts Payable to Subsidiaries 4,333 8,432 Other Current Liabilities 62,385 57,877 Total Current Liabilities 969,235 1,076,692 Deferred Credits and Other Liabilities 149,637 134,614 Long-Term Debt 4,358,339 4,031,997 Common Shareholders' Equity: Common Shares 1,729,292 1,669,392 Capital Surplus, Paid in 7,087,768 6,241,222 Retained Earnings 4,177,048 3,953,974 Accumulated Other Comprehensive Loss (65,059 ) (60,000 ) Treasury Stock (299,055 ) (317,771 ) Common Shareholders' Equity 12,629,994 11,486,817 Total Liabilities and Capitalization $ 18,107,205 $ 16,730,120 See the Combined Notes to Financial Statements in this Annual Report on Form 10-K for a description of significant accounting matters related to Eversource parent, including Eversource common shares information as described in Note 19, "Common Shares," material obligations and guarantees as described in Note 13, "Commitments and Contingencies," and debt agreements as described in Note 8, "Short-Term Debt," and Note 9, "Long-Term Debt." SCHEDULE I EVERSOURCE ENERGY (PARENT) FINANCIAL INFORMATION OF REGISTRANT STATEMENTS OF INCOME FOR THE YEARS ENDED DECEMBER 31, 2019 , 2018 AND 2017 (Thousands of Dollars, Except Share Information) 2019 2018 2017 Operating Revenues $ — $ — $ — Operating Expenses: Other 50,100 (6,552 ) (32,189 ) Operating (Loss)/Income (50,100 ) 6,552 32,189 Interest Expense 163,937 123,638 80,700 Other Income, Net: Equity in Earnings of Subsidiaries 1,001,526 1,049,748 993,063 Other, Net 68,137 47,581 23,339 Other Income, Net 1,069,663 1,097,329 1,016,402 Income Before Income Tax Benefit 855,626 980,243 967,891 Income Tax Benefit (53,427 ) (52,757 ) (20,105 ) Net Income $ 909,053 $ 1,033,000 $ 987,996 Basic Earnings per Common Share $ 2.83 $ 3.25 $ 3.11 Diluted Earnings per Common Share $ 2.81 $ 3.25 $ 3.11 Weighted Average Common Shares Outstanding: Basic 321,416,086 317,370,369 317,411,097 Diluted 322,941,636 317,993,934 318,031,580 STATEMENTS OF COMPREHENSIVE INCOME 2019 2018 2017 Net Income $ 909,053 $ 1,033,000 $ 987,996 Other Comprehensive (Loss)/Income, Net of Tax: Qualified Cash Flow Hedging Instruments 1,393 1,756 1,974 Changes in Unrealized Gains/(Losses) on Marketable Securities 1,166 (547 ) (350 ) Change in Funded Status of Pension, SERP and PBOP Benefit Plans (7,618 ) 5,194 (2,745 ) Other Comprehensive (Loss)/Income, Net of Tax (5,059 ) 6,403 (1,121 ) Comprehensive Income $ 903,994 $ 1,039,403 $ 986,875 See the Combined Notes to Financial Statements in this Annual Report on Form 10-K for a description of significant accounting matters related to Eversource parent, including Eversource common shares information as described in Note 19, "Common Shares," material obligations and guarantees as described in Note 13, "Commitments and Contingencies," and debt agreements as described in Note 8, "Short-Term Debt," and Note 9, "Long-Term Debt." SCHEDULE I EVERSOURCE ENERGY (PARENT) FINANCIAL INFORMATION OF REGISTRANT STATEMENTS OF CASH FLOWS FOR THE YEARS ENDED DECEMBER 31, 2019 , 2018 and 2017 (Thousands of Dollars) 2019 2018 2017 Operating Activities: Net Income $ 909,053 $ 1,033,000 $ 987,996 Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities: Equity in Earnings of Subsidiaries (1,001,526 ) (1,049,748 ) (993,063 ) Cash Dividends Received from Subsidiaries 883,000 569,500 753,300 Deferred Income Taxes 13,382 20,032 37,867 Other 19,584 (31,093 ) (36,052 ) Changes in Current Assets and Liabilities: Accounts Receivables from Subsidiaries 7,105 (28,716 ) 29,405 Taxes Receivable/Accrued, Net (605 ) (20,207 ) 1,555 Accounts Payable to Subsidiaries (4,099 ) (9,817 ) 9,763 Other Current Assets and Liabilities, Net (2,503 ) 2,553 7,536 Net Cash Flows Provided by Operating Activities 823,391 485,504 798,307 Investing Activities: Capital Contributions to Subsidiaries (1,039,000 ) (955,700 ) (1,156,731 ) Return of Capital from Subsidiary — 530,000 — Increase in Notes Receivable from Subsidiaries (218,100 ) (158,210 ) (192,100 ) Other Investing Activities (1,799 ) (1,149 ) 1,484 Net Cash Flows Used in Investing Activities (1,258,899 ) (585,059 ) (1,347,347 ) Financing Activities: Issuance of Common Shares, Net of Issuance Costs 852,254 — — Cash Dividends on Common Shares (663,239 ) (640,110 ) (602,083 ) Issuance of Long-Term Debt — 1,550,000 1,200,000 Retirement of Long-Term Debt (350,000 ) (450,000 ) — Increase/(Decrease) in Notes Payable 593,370 (347,810 ) (42,690 ) Other Financing Activities 4,001 (12,455 ) (5,759 ) Net Cash Flows Provided by Financing Activities 436,386 99,625 549,468 Net Increase in Cash 878 70 428 Cash - Beginning of Year 591 521 93 Cash - End of Year $ 1,469 $ 591 $ 521 Supplemental Cash Flow Information: Cash Paid/(Received) During the Year for: Interest $ 161,323 $ 118,533 $ 73,868 Income Taxes $ (63,227 ) $ (30,239 ) $ (59,526 ) See the Combined Notes to Financial Statements in this Annual Report on Form 10-K for a description of significant accounting matters related to Eversource parent, including Eversource common shares information as described in Note 19, "Common Shares," material obligations and guarantees as described in Note 13, "Commitments and Contingencies," and debt agreements as described in Note 8, "Short-Term Debt," and Note 9, "Long-Term Debt."

SCHEDULE II - VALUATION AND QUA

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES	SCHEDULE II EVERSOURCE ENERGY AND SUBSIDIARIES VALUATION AND QUALIFYING ACCOUNTS AND RESERVES FOR THE YEARS ENDED DECEMBER 31, 2019 , 2018 AND 2017 (Thousands of Dollars) Column A Column B Column C Column D Column E Additions (1) (2) Charged Charged to Balance as to Costs Other Deductions - Balance of Beginning and Accounts - Describe as of Description: of Year Expenses Describe (a) (b) End of Year Eversource : Reserves Deducted from Assets - Reserves for Uncollectible Accounts: 2019 $ 212,723 $ 63,446 $ 57,223 $ 108,571 $ 224,821 2018 195,708 61,337 48,671 92,993 212,723 2017 200,630 44,665 47,630 97,217 195,708 CL&P: Reserves Deducted from Assets - Reserves for Uncollectible Accounts: 2019 $ 88,034 $ 15,947 $ 38,935 $ 45,568 $ 97,348 2018 78,872 15,831 29,524 36,193 88,034 2017 86,391 5,312 25,533 38,364 78,872 NSTAR Electric: Reserves Deducted from Assets - Reserves for Uncollectible Accounts: 2019 $ 74,516 $ 25,079 $ 12,556 $ 36,745 $ 75,406 2018 69,666 22,279 14,971 32,400 74,516 2017 70,284 21,252 14,273 36,143 69,666 PSNH : Reserves Deducted from Assets - Reserves for Uncollectible Accounts: 2019 $ 11,065 $ 6,726 $ 872 $ 8,166 $ 10,497 2018 10,481 6,383 953 6,752 11,065 2017 9,941 6,917 464 6,841 10,481 (a) Amounts relate to uncollectible accounts receivables reserved for that are not charged to bad debt expense. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows NSTAR Electric and NSTAR Gas to recover in rates, amounts associated with certain uncollectible hardship accounts receivable. (b)

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements of Eversource, NSTAR Electric and PSNH include the accounts of each of their respective subsidiaries. Intercompany transactions have been eliminated in consolidation. The accompanying consolidated financial statements of Eversource, NSTAR Electric and PSNH and the financial statements of CL&P are herein collectively referred to as the "financial statements." The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Eversource consolidates the operations of CYAPC and YAEC, both of which are inactive regional nuclear generation companies engaged in the long-term storage of their spent nuclear fuel. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's and PSNH's combined ownership and voting interests in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and the CYAPC and YAEC companies have been eliminated in consolidation of the Eversource financial statements. Eversource's consolidated financial information includes the results of Aquarion and its subsidiaries beginning from the date of the acquisition on December 4, 2017. Eversource holds several equity ownership interests that are not consolidated and are accounted for under the equity method. In accordance with accounting guidance on noncontrolling interests in consolidated financial statements, the Preferred Stock of CL&P and the Preferred Stock of NSTAR Electric, which are not owned by Eversource or its consolidated subsidiaries and are not subject to mandatory redemption, have been presented as noncontrolling interests in the financial statements of Eversource. The Preferred Stock of CL&P and the Preferred Stock of NSTAR Electric are considered to be temporary equity and have been classified between liabilities and permanent shareholders' equity on the balance sheets of Eversource, CL&P and NSTAR Electric due to a provision in the preferred stock agreements of both CL&P and NSTAR Electric that grant preferred stockholders the right to elect a majority of the CL&P and NSTAR Electric Boards of Directors, respectively, should certain conditions exist, such as if preferred dividends are in arrears for a specified amount of time. The Net Income reported in the statements of income and cash flows represents net income prior to apportionment to noncontrolling interests, which is represented by dividends on preferred stock of CL&P and NSTAR Electric. Eversource's utility subsidiaries' electric, natural gas and water distribution and transmission businesses are subject to rate-regulation that is based on cost recovery and meets the criteria for application of accounting guidance for entities with rate-regulated operations, which considers the effect of regulation on the differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. See Note 2, "Regulatory Accounting," for further information. Certain reclassifications of prior year data were made in the accompanying financial statements to conform to the current year presentation. The Eversource and PSNH 2018 statements of cash flows, the 2018 supplemental cash flow information footnote, and the 2018 segment footnote were revised to correct an error in the presentation of non-cash capital additions. The impact of this revision on the statement of cash flows is an increase to operating cash inflows in Accounts Payable of $46.6 million and a corresponding increase to investing cash outflows in Investments in Property, Plant and Equipment for the year ended December 31, 2018. This revision is not deemed material, individually or in the aggregate, to the previously issued financial statements.
Accounting Standards	Accounting Standards Accounting Standards Issued but Not Yet Effective: In June 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326), which provides a new model for recognizing credit losses on financial instruments based on an estimate of current expected credit losses. Under the new guidance, immediate recognition of credit losses expected over the life of a financial instrument is required. The standard is effective January 1, 2020. The Company assessed the impacts of this standard on the accounting for credit losses on its financial instruments, including accounts receivable, and does not expect a material impact on the financial statements of Eversource, CL&P, NSTAR Electric or PSNH. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes , which eliminates certain exceptions to the general principles of current income tax guidance in ASC 740, Income Taxes, and simplifies and improves consistency in application of that income tax guidance through clarifications of, and amendments to, ASC 740. The guidance is effective in the first quarter of 2021. The Company is evaluating the impact of this standard on the financial statements of Eversource, CL&P, NSTAR Electric and PSNH. Accounting Standards Recently Adopted: On January 1, 2019, the Company adopted ASU 2016-02, Leases (Topic 842), which amended existing lease accounting guidance. The Company applied the Topic 842 lease criteria to new leases and lease renewals entered into effective on or after January 1, 2019. The ASU required balance sheet recognition of leases deemed to be operating leases as well as additional disclosure requirements. The recognition, measurement and presentation of expenses and cash flows were not significantly changed. The Company utilized the modified retrospective transition method allowed in ASU 2018-11, Leases (Topic 842) - Targeted Improvements , which allowed the Company to adopt the new leases standard as of January 1, 2019, with prior periods presented in the financial statements continuing to follow existing lease accounting guidance under Topic 840 (Leases) in the accounting literature. Implementation of ASU 2018-11 had no effect on retained earnings, and the requirements of the new lease standard (Topic 842) are reflected in the 2019 financial statements and footnotes. The Company elected the practical expedient package whereby it did not need to reassess whether or not an existing contract is or contains a lease or whether a lease is an operating or capital lease, and it did not need to reassess initial direct costs for leases. Election of this practical expedient allowed us to carry forward our historical lease classifications. The Company elected the practical expedient to not reevaluate land easements existing at adoption if they were not previously accounted for as leases. The Company also elected to use the discount rate as of the January 1, 2019 implementation date to discount its operating lease liabilities. The Company did not elect the hindsight practical expedient to determine the lease term for existing leases. The Company determined the impact the ASUs had on its financial statements by reviewing its lease population and identifying lease data needed for the disclosure requirements. The Company implemented a new lease accounting system in 2019 to ensure ongoing compliance with the ASU’s requirements. Adoption of the new standard resulted in the recording of operating lease liabilities and right-of-use assets on the balance sheet upon transition at January 1, 2019 of $58.0 million at Eversource, $25.3 million at NSTAR Electric, $0.6 million at CL&P, and $0.6 million at PSNH. Implementation of the new guidance did not have an impact on each company’s results of operations or cash flows.
Cash	Cash Cash includes cash on hand. At the end of each reporting period, any overdraft amounts are reclassified from Cash to Accounts Payable on the balance sheets.
Provision for Uncollectible Accounts	Provision for Uncollectible Accounts Eversource, including CL&P, NSTAR Electric and PSNH, presents its receivables at estimated net realizable value by maintaining a provision for uncollectible accounts. This provision is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. The estimate is based upon historical collection and write-off experience and management's assessment of collectability from customers. Management continuously assesses the collectability of receivables and adjusts collectability estimates based on actual experience. Receivable balances are written off against the provision for uncollectible accounts when the customer accounts are terminated and these balances are deemed to be uncollectible. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows NSTAR Electric and NSTAR Gas to recover in rates, amounts associated with certain uncollectible hardship accounts receivable. These uncollectible hardship customer account balances are included in Regulatory Assets or Other Long-Term Assets on the balance sheets.
Transfer of Energy Efficiency Loans	Transfer of Energy Efficiency Loans In 2018, CL&P transferred $41.3 million of its energy efficiency customer loan portfolio to two outside lenders in order to make additional loans to customers. CL&P remains the servicer of the loans and will transmit customer payments to the lenders. Under a three -year agreement with the lenders, additional energy efficiency loans will also be transferred with a maximum amount outstanding under this program of $55 million
Fuel, Materials, Supplies and REC Inventory	Fuel, Materials, Supplies and REC InventoryFuel, Materials, Supplies and REC Inventory include natural gas inventory, materials and supplies purchased primarily for construction or operation and maintenance purposes, and RECs. Inventory is valued at the lower of cost or net realizable value. RECs are purchased from suppliers of renewable sources of generation and are used to meet state mandated Renewable Portfolio Standards requirements.
Fair Value Measurements	Fair Value Measurements Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases" or "normal sales" (normal) and to the marketable securities held in trusts. Fair value measurement guidance is also applied to valuations of the investments used to calculate the funded status of pension and PBOP plans, the nonrecurring fair value measurements of nonfinancial assets such as goodwill, long-lived assets and AROs. We also applied this guidance in the valuation of our basis differences in our equity method offshore wind investments (see Note 6, "Investments in Unconsolidated Affiliates," for further information). The fair value measurement guidance was also applied in estimating the fair value of preferred stock, long-term debt and RRBs. Fair Value Hierarchy: In measuring fair value, Eversource uses observable market data when available in order to minimize the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. Eversource evaluates the classification of assets and liabilities measured at fair value on a quarterly basis, and Eversource's policy is to recognize transfers between levels of the fair value hierarchy as of the end of the reporting period. The three levels of the fair value hierarchy are described below: Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable. Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products. Uncategorized - Investments that are measured at net asset value are not categorized within the fair value hierarchy.
Derivative Accounting	Derivative Accounting Many of the electric and natural gas companies' contracts for the purchase and sale of energy or energy-related products are derivatives. The accounting treatment for energy contracts entered into varies and depends on the intended use of the particular contract and on whether or not the contract is a derivative. The application of derivative accounting is complex and requires management judgment in the following respects: identification of derivatives and embedded derivatives, election and designation of a contract as normal, and determination of the fair value of derivative contracts. All of these judgments can have a significant impact on the financial statements. The judgment applied in the election of a contract as normal (and resulting accrual accounting) includes the conclusion that it is probable at the inception of the contract and throughout its term that it will result in physical delivery of the underlying product and that the quantities will be used or sold by the business in the normal course of business. If facts and circumstances change and management can no longer support this conclusion, then a contract cannot be considered normal, accrual accounting is terminated, and fair value accounting is applied prospectively. The fair value of derivative contracts is based upon the contract terms and conditions and the underlying market price or fair value per unit. When quantities are not specified in the contract, the Company determines whether the contract has a determinable quantity by using amounts referenced in default provisions and other relevant sections of the contract. The fair value of derivative assets and liabilities with the same counterparty are offset and recorded as a net derivative asset or liability on the balance sheets. Regulatory assets or regulatory liabilities are recorded to offset the fair values of derivative contracts related to energy and energy-related products, as contract settlements are recovered from, or refunded to, customers in future rates. All changes in the fair value of derivative contracts are recorded as regulatory assets or liabilities and do not impact net income.
Allowance for Funds Used During Construction	Allowance for Funds Used During Construction AFUDC represents the cost of borrowed and equity funds used to finance construction and is included in the cost of the electric, natural gas and water companies' utility plant on the balance sheet. The portion of AFUDC attributable to borrowed funds is recorded as a reduction of Interest Expense, and the AFUDC related to equity funds is recorded as Other Income, Net on the statements of income. AFUDC costs are recovered from customers over the service life of the related plant in the form of increased revenue collected as a result of higher depreciation expense. The average AFUDC rate is based on a FERC-prescribed formula using the cost of a company's short-term financings and capitalization (preferred stock, long-term debt and common equity), as appropriate. The average rate is applied to average eligible CWIP amounts to calculate AFUDC.
Other Taxes	Other TaxesEversource's companies that serve customers in Connecticut collect gross receipts taxes levied by the state of Connecticut from their customers. As agents for state and local governments, Eversource's companies that serve customers in Connecticut and Massachusetts collect certain sales taxes that are recorded on a net basis with no impact on the statements of income. Separate from above were amounts recorded as Taxes Other Than Income Taxes related to the remittance to the State of Connecticut of energy efficiency funds collected from customers in Operating Revenues. These amounts were $21.4 million and $46.8 million in 2019 and 2018, respectively. Energy efficiency funds collected from customers after July 1, 2019 are no longer subject to remittance to the State of Connecticut. These amounts were recorded separately, with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the Eversource and CL&P statements of income.
Related Parties	Related Parties Eversource Service, Eversource's service company, provides centralized accounting, administrative, engineering, financial, information technology, legal, operational, planning, purchasing, tax, and other services to Eversource's companies. The Rocky River Realty Company, Renewable Properties, Inc. and Properties, Inc., three other Eversource subsidiaries, construct, acquire or lease some of the property and facilities used by Eversource's companies. As of both December 31, 2019 and 2018 , CL&P, NSTAR Electric and PSNH had long-term receivables from Eversource Service in the amounts of $25.0 million , $5.5 million and $3.8 million , respectively, which were included in Other Long-Term Assets on the balance sheets. These amounts related to the funding of investments held in trust by Eversource Service in connection with certain postretirement benefits for CL&P, NSTAR Electric and PSNH employees and have been eliminated in consolidation on the Eversource financial statements. Included in the CL&P, NSTAR Electric and PSNH balance sheets as of December 31, 2019 and 2018 were Accounts Receivable from Affiliated Companies and Accounts Payable to Affiliated Companies relating to transactions between CL&P, NSTAR Electric and PSNH and other subsidiaries that are wholly-owned by Eversource. These amounts have been eliminated in consolidation on the Eversource financial statements.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	Dec. 31, 2019
Accounting Policies [Abstract]
Provision for Uncollectible Accounts	The provision balances were as follows: Total Provision for Uncollectible Accounts Provision for Uncollectible Hardship Accounts As of December 31, As of December 31, (Millions of Dollars) 2019 2018 2019 2018 Eversource $ 224.8 $ 212.7 $ 143.3 $ 131.5 CL&P 97.3 88.0 80.1 71.9 NSTAR Electric 75.4 74.5 43.9 42.5 PSNH 10.5 11.1 — — Uncollectible expense associated with customers' accounts receivable included in Operations and Maintenance expense on the statements of income was as follows: For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Eversource $ 63.4 $ 61.3 $ 44.5 CL&P 15.9 15.8 5.3 NSTAR Electric 25.1 22.3 21.3 PSNH 6.7 6.4 6.7
Schedule of Utility Inventory	The carrying amounts of fuel, materials and supplies, and RECs, which are included in Current Assets on the balance sheets, were as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Fuel $ 26.7 $ — $ — $ — $ 33.1 $ — $ — $ — Materials and Supplies 132.9 50.7 54.7 18.5 126.1 44.5 48.6 24.3 RECs 75.9 — 69.4 6.5 78.8 — 65.6 13.2 Total $ 235.5 $ 50.7 $ 124.1 $ 25.0 $ 238.0 $ 44.5 $ 114.2 $ 37.5
Costs related to fuel and natural gas	Costs related to fuel and natural gas included in Purchased Power, Fuel and Transmission on the statements of income were as follows: For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Eversource - Natural Gas and Fuel $ 462.1 $ 442.6 $ 432.5 PSNH - Fuel — 7.9 43.4
Weighted-average AFUDC rates	AFUDC costs and the weighted-average AFUDC rates were as follows: Eversource For the Years Ended December 31, (Millions of Dollars, except percentages) 2019 2018 2017 Borrowed Funds $ 25.6 $ 19.7 $ 12.5 Equity Funds 45.0 44.0 34.4 Total AFUDC $ 70.6 $ 63.7 $ 46.9 Average AFUDC Rate 5.4 % 4.9 % 5.1 % For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars, except percentages) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Borrowed Funds $ 7.1 $ 10.4 $ 2.8 $ 6.3 $ 7.8 $ 1.3 $ 5.1 $ 4.8 $ 0.7 Equity Funds 13.2 19.8 3.4 12.2 15.6 — 12.1 10.2 — Total AFUDC $ 20.3 $ 30.2 $ 6.2 $ 18.5 $ 23.4 $ 1.3 $ 17.2 $ 15.0 $ 0.7 Average AFUDC Rate 6.3 % 5.7 % 4.6 % 5.8 % 5.0 % 0.7 % 6.2 % 5.0 % 0.7 %
Components of Other Income, Net	The components of Other Income, Net on the statements of income were as follows: Eversource For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Pension, SERP and PBOP Non-Service Income Components $ 31.3 $ 60.8 $ 29.9 AFUDC Equity 45.0 44.0 34.4 Equity in Earnings of Unconsolidated Affiliates (1) 42.2 3.8 27.4 Investment Income/(Loss) 0.8 (4.0 ) 7.5 Interest Income (2) 12.8 18.1 8.3 Gains on Sales of Property 0.3 5.1 — Other 0.4 0.6 0.4 Total Other Income, Net $ 132.8 $ 128.4 $ 107.9 For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service Income Components $ 0.5 $ 23.5 $ 4.9 $ 9.5 $ 36.0 $ 9.9 $ 1.8 $ 19.2 $ 5.9 AFUDC Equity 13.2 19.8 3.4 12.2 15.6 — 12.1 10.2 — Equity in Earnings of Unconsolidated Affiliates 0.1 0.7 — 0.1 0.7 — — 0.3 — Investment Income/(Loss) 2.3 (0.4 ) 0.3 (3.0 ) (0.5 ) (0.8 ) 4.5 2.6 1.6 Interest Income (2) 1.5 0.7 10.5 3.7 0.8 14.1 4.6 1.8 2.2 Gains on Sales of Property — 0.1 — — 0.5 4.4 — — — Other (0.1 ) 0.2 0.1 0.2 — 0.1 — — 0.1 Total Other Income, Net $ 17.5 $ 44.6 $ 19.2 $ 22.7 $ 53.1 $ 27.7 $ 23.0 $ 34.1 $ 9.8 (1) Equity in earnings of unconsolidated affiliates includes an other-than-temporary impairment of $32.9 million of the Access Northeast project investment for the year ended December 31, 2018. See Note 6, "Investments in Unconsolidated Affiliates," for further information. Equity in earnings includes $20.4 million , $17.6 million and $9.7 million of pre-tax unrealized gains for the years ended December 31, 2019 , 2018 and 2017 , respectively, associated with an equity method investment in a renewable energy fund. (2) For the years ended December 31, 2019 and 2018, PSNH recognized $6.3 million and $8.7 million , respectively, of interest income for the equity return component of carrying charges on storm costs approved in 2019 and 2018. See Note 2, "Regulatory Accounting," for further information.
Other Taxes	These gross receipts taxes are recorded separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of income as follows: For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Eversource $ 163.1 $ 161.9 $ 157.4 CL&P 141.1 141.4 137.5
Supplemental Cash Flow Information	Eversource (Millions of Dollars) As of and For the Years Ended December 31, 2019 2018 2017 Cash Paid During the Year for: Interest, Net of Amounts Capitalized $ 532.4 $ 503.2 $ 419.1 Income Taxes 56.0 158.8 30.8 Non-Cash Investing Activities: Plant Additions Included in Accounts Payable (As of) (1) 379.4 389.3 379.5 As of and For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Cash Paid During the Year for: Interest, Net of Amounts Capitalized $ 144.6 $ 121.9 $ 56.9 $ 149.7 $ 122.1 $ 40.5 $ 144.6 $ 124.6 $ 45.9 Income Taxes 80.6 77.9 3.4 66.1 120.0 27.3 68.8 95.5 26.1 Non-Cash Investing Activities: Plant Additions Included in Accounts Payable (As of) (1) 111.3 116.4 49.9 106.1 116.5 35.1 132.5 116.5 44.4 (1) See Note 1B, "Summary of Significant Accounting Policies - Basis of Presentation," for information regarding the correction of non-cash capital additions at Eversource and PSNH reported as of December 31, 2018.
Cash and cash equivalents as reported on the balance sheet	The following table reconciles cash as reported on the balance sheets to the cash and restricted cash balance as reported on the statements of cash flows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Cash as reported on the Balance Sheets $ 15.4 $ — $ 0.1 $ 0.4 $ 108.1 $ 87.7 $ 1.6 $ 1.4 Restricted cash included in: Special Deposits 52.5 4.6 6.2 32.5 72.1 3.5 13.0 47.5 Marketable Securities 46.0 0.4 — 0.6 25.9 0.4 0.1 0.6 Other Long-Term Assets 3.2 — — 3.2 3.2 — — 3.2 Cash and Restricted Cash reported on the Statements of Cash Flows $ 117.1 $ 5.0 $ 6.3 $ 36.7 $ 209.3 $ 91.6 $ 14.7 $ 52.7

REGULATORY ACCOUNTING (Tables)

REGULATORY ACCOUNTING (Tables)	12 Months Ended
REGULATORY ACCOUNTING (Tables)	Dec. 31, 2019
Regulated Operations [Abstract]
Components of Regulatory Assets	The components of regulatory assets were as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Benefit Costs $ 2,382.9 $ 539.0 $ 629.8 $ 218.2 $ 1,914.8 $ 424.7 $ 544.4 $ 169.6 Income Taxes, Net 725.8 458.8 108.0 12.8 728.6 454.4 105.9 8.3 Securitized Stranded Costs 565.3 — — 565.3 608.4 — — 608.4 Storm Restoration Costs, Net 540.6 274.6 200.6 65.4 576.0 302.6 212.9 60.5 Regulatory Tracker Mechanisms 411.5 78.3 207.1 65.8 316.0 33.2 169.1 67.3 Derivative Liabilities 334.5 329.2 — — 356.5 356.5 — — Goodwill-related 331.5 — 284.6 — 348.4 — 299.1 — Asset Retirement Obligations 97.2 30.8 50.3 3.6 89.2 32.3 42.2 3.3 Other Regulatory Assets 125.4 25.2 55.2 14.7 208.0 27.0 64.6 12.1 Total Regulatory Assets 5,514.7 1,735.9 1,535.6 945.8 5,145.9 1,630.7 1,438.2 929.5 Less: Current Portion 651.1 178.6 285.6 84.1 514.8 125.2 241.7 67.2 Total Long-Term Regulatory Assets $ 4,863.6 $ 1,557.3 $ 1,250.0 $ 861.7 $ 4,631.1 $ 1,505.5 $ 1,196.5 $ 862.3
Components of Regulatory Liabilities	The components of regulatory liabilities were as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH EDIT due to Tax Cuts and Jobs Act $ 2,844.6 $ 1,022.8 $ 1,071.2 $ 392.8 $ 2,883.0 $ 1,031.0 $ 1,103.7 $ 396.4 Cost of Removal 559.8 64.6 330.6 16.3 521.0 39.9 307.1 22.1 Benefit Costs 84.5 — 72.2 — 91.2 — 76.9 — Regulatory Tracker Mechanisms 325.1 94.8 165.6 57.0 309.0 89.5 163.7 48.3 AFUDC - Transmission 73.2 46.0 27.2 — 70.7 47.4 23.3 — Revenue Subject to Refund due to Tax Cuts and Jobs Act 14.6 — — 6.0 24.6 — — 12.6 Other Regulatory Liabilities 117.4 19.6 59.0 7.1 80.2 24.0 29.2 4.2 Total Regulatory Liabilities 4,019.2 1,247.8 1,725.8 479.2 3,979.7 1,231.8 1,703.9 483.6 Less: Current Portion 361.2 82.8 209.2 65.8 370.2 109.6 190.6 55.5 Total Long-Term Regulatory Liabilities $ 3,658.0 $ 1,165.0 $ 1,516.6 $ 413.4 $ 3,609.5 $ 1,122.2 $ 1,513.3 $ 428.1

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Utility Property, Plant and Equipment	The following tables summarize property, plant and equipment by asset category: Eversource As of December 31, (Millions of Dollars) 2019 2018 Distribution - Electric $ 15,880.0 $ 15,071.1 Distribution - Natural Gas 3,931.1 3,546.2 Transmission - Electric 10,958.4 10,153.9 Distribution - Water 1,726.5 1,639.8 Solar 200.2 164.1 Utility 32,696.2 30,575.1 Other (1) 1,025.6 778.6 Property, Plant and Equipment, Gross 33,721.8 31,353.7 Less: Accumulated Depreciation Utility (7,483.5 ) (7,126.2 ) Other (387.4 ) (336.7 ) Total Accumulated Depreciation (7,870.9 ) (7,462.9 ) Property, Plant and Equipment, Net 25,850.9 23,890.8 Construction Work in Progress 1,734.6 1,719.6 Total Property, Plant and Equipment, Net $ 27,585.5 $ 25,610.4 As of December 31, 2019 2018 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Distribution - Electric $ 6,485.5 $ 7,163.7 $ 2,271.1 $ 6,176.4 $ 6,756.4 $ 2,178.6 Transmission - Electric 5,043.0 4,411.9 1,498.7 4,700.5 4,065.9 1,338.7 Solar — 200.2 — — 164.1 — Property, Plant and Equipment, Gross 11,528.5 11,775.8 3,769.8 10,876.9 10,986.4 3,517.3 Less: Accumulated Depreciation (2,385.7 ) (2,895.3 ) (799.9 ) (2,302.6 ) (2,702.0 ) (772.9 ) Property, Plant and Equipment, Net 9,142.8 8,880.5 2,969.9 8,574.3 8,284.4 2,744.4 Construction Work in Progress 483.0 592.3 159.6 335.4 510.3 135.7 Total Property, Plant and Equipment, Net $ 9,625.8 $ 9,472.8 $ 3,129.5 $ 8,909.7 $ 8,794.7 $ 2,880.1 (1) These assets are primarily comprised of computer software, hardware and equipment at Eversource Service and buildings at The Rocky River Realty Company. The depreciation rates for the various classes of utility property, plant and equipment aggregate to composite rates as follows: (Percent) 2019 2018 2017 Eversource 3.0 % 2.9 % 3.0 % CL&P 2.8 % 2.8 % 2.8 % NSTAR Electric 2.8 % 2.8 % 2.9 % PSNH 2.8 % 2.8 % 3.1 % The following table summarizes average remaining useful lives of depreciable assets: As of December 31, 2019 (Years) Eversource CL&P NSTAR Electric PSNH Distribution - Electric 34.3 35.3 33.7 33.2 Distribution - Natural Gas 43.2 — — — Transmission - Electric 40.4 36.8 44.9 42.1 Distribution - Water 33.5 — — — Solar 24.2 — 24.2 — Other (1) 11.2 — — — (1) The estimated useful life of computer software, hardware and equipment primarily ranges from 5 to 15 years and of buildings is 40 years .

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	12 Months Ended
DERIVATIVE INSTRUMENTS (Tables)	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table presents the gross fair values of contracts, categorized by risk type, and the net amounts recorded as current or long-term derivative assets or liabilities: As of December 31, 2019 2018 (Millions of Dollars) Fair Value Hierarchy Commodity Supply and Price Risk Management Netting (1) Net Amount Recorded as a Derivative Commodity Supply and Price Risk Management Netting (1) Net Amount Recorded as a Derivative Current Derivative Assets: CL&P Level 3 $ 12.2 $ (0.4 ) $ 11.8 $ 9.6 $ (3.4 ) $ 6.2 Other Level 2 — — — 1.5 (0.9 ) 0.6 Long-Term Derivative Assets: CL&P Level 3 67.5 (2.1 ) 65.4 74.2 (2.3 ) 71.9 Current Derivative Liabilities: CL&P Level 3 (67.8 ) — (67.8 ) (55.1 ) — (55.1 ) Other Level 2 (5.2 ) — (5.2 ) — — — Long-Term Derivative Liabilities : CL&P Level 3 (338.6 ) — (338.6 ) (379.5 ) — (379.5 ) Other Level 2 (0.1 ) — (0.1 ) — — — (1) Amounts represent derivative assets and liabilities that Eversource elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists.
Fair Value Inputs, Liabilities, Quantitative Information	The following is a summary of Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts: As of December 31, 2019 2018 CL&P Range Period Covered Range Period Covered Capacity Prices $ 3.01 — 7.34 per kW-Month 2023 - 2026 $ 4.30 — 7.44 per kW-Month 2022 - 2026 Forward Reserve 0.80 — 1.90 per kW-Month 2020 - 2024 0.75 — 1.78 per kW-Month 2019 - 2024
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation	The following table presents changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis. CL&P (Millions of Dollars) For the Years Ended December 31, 2019 2018 Derivatives, Net: Fair Value as of Beginning of Period $ (356.5 ) $ (362.3 ) Net Realized/Unrealized Losses Included in Regulatory Assets (15.0 ) (32.0 ) Settlements 42.3 37.8 Fair Value as of End of Period $ (329.2 ) $ (356.5 )

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	12 Months Ended
MARKETABLE SECURITIES (Tables)	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities Reconciliation	The following is a summary of the available-for-sale debt securities, which are recorded at fair value and are included in current and long-term Marketable Securities on the balance sheets. As of December 31, 2019 2018 Eversource (Millions of Dollars) Amortized Pre-Tax Pre-Tax Fair Value Amortized Pre-Tax Pre-Tax Fair Value Debt Securities $ 228.4 $ 5.8 $ (0.1 ) $ 234.1 $ 190.0 $ 0.4 $ (4.0 ) $ 186.4
Investments Classified by Contractual Maturity Date	As of December 31, 2019 , the contractual maturities of available-for-sale debt securities were as follows: Eversource (Millions of Dollars) Amortized Cost Fair Value Less than one year (1) $ 59.2 $ 59.3 One to five years 40.5 41.4 Six to ten years 33.6 34.8 Greater than ten years 95.1 98.6 Total Debt Securities $ 228.4 $ 234.1 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC spent nuclear fuel trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets.
Marketable Securities Recorded at Fair Value	The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Eversource (Millions of Dollars) As of December 31, 2019 2018 Level 1: Mutual Funds and Equities $ 228.5 $ 244.0 Money Market Funds 46.0 25.9 Total Level 1 $ 274.5 $ 269.9 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 96.8 $ 79.6 Corporate Debt Securities 44.0 39.5 Asset-Backed Debt Securities 12.9 14.0 Municipal Bonds 26.7 19.2 Other Fixed Income Securities 7.7 8.2 Total Level 2 $ 188.1 $ 160.5 Total Marketable Securities $ 462.6 $ 430.4

ASSET RETIREMENT OBLIGATIONS (T

ASSET RETIREMENT OBLIGATIONS (Tables)	12 Months Ended
ASSET RETIREMENT OBLIGATIONS (Tables)	Dec. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]
Schedule of Change in Asset Retirement Obligation	A reconciliation of the beginning and ending carrying amounts of ARO liabilities is as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Balance as of Beginning of Year $ 466.2 $ 33.5 $ 72.4 $ 4.0 $ 419.1 $ 31.5 $ 44.6 $ 25.0 Liabilities Incurred During the Year 30.3 — 30.3 — 11.3 — 11.3 — Liabilities Settled During the Year (21.3 ) (3.6 ) — — (36.6 ) — — (21.5 ) Accretion 27.1 2.2 3.5 0.2 25.5 2.0 2.2 0.5 Revisions in Estimated Cash Flows (12.8 ) (0.1 ) (8.7 ) — 46.9 — 14.3 — Balance as of End of Year $ 489.5 $ 32.0 $ 97.5 $ 4.2 $ 466.2 $ 33.5 $ 72.4 $ 4.0

INVESTMENTS IN UNCONSOLIDATED_2

INVESTMENTS IN UNCONSOLIDATED AFFILIATES (Tables)	12 Months Ended
INVESTMENTS IN UNCONSOLIDATED AFFILIATES (Tables)	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Summary of Investments	Eversource's investments included the following: Investment Balance as of December 31, (Millions of Dollars) Ownership Interest 2019 2018 Offshore Wind Business - North East Offshore and Bay State Wind 50 % $ 649.3 $ 234.3 Natural Gas Pipeline - Algonquin Gas Transmission, LLC 15 % 127.8 155.0 Renewable Energy Investment Fund 90 % 72.4 54.1 Other various 22.1 20.9 Total Investments in Unconsolidated Affiliates $ 871.6 $ 464.3

SHORT-TERM DEBT (Tables)

SHORT-TERM DEBT (Tables)	12 Months Ended
SHORT-TERM DEBT (Tables)	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Borrowings Outstanding	The amount of borrowings outstanding and available under the commercial paper programs were as follows: Borrowings Outstanding as of December 31, Available Borrowing Capacity as of December 31, Weighted-Average Interest Rate as of December 31, (Millions of Dollars) 2019 2018 2019 2018 2019 2018 Eversource Parent Commercial Paper Program $ 1,224.9 $ 631.5 $ 225.1 $ 818.5 1.98 % 2.77 % NSTAR Electric Commercial Paper Program 10.5 278.5 639.5 371.5 1.63 % 2.50 % Details of long-term debt outstanding are as follows: CL&P (Millions of Dollars) As of December 31, 2019 2018 First Mortgage Bonds: 7.875% 1994 Series D due 2024 $ 139.8 $ 139.8 5.750% 2004 Series B due 2034 130.0 130.0 5.625% 2005 Series B due 2035 100.0 100.0 6.350% 2006 Series A due 2036 250.0 250.0 5.750% 2007 Series B due 2037 150.0 150.0 6.375% 2007 Series D due 2037 100.0 100.0 5.500% 2009 Series A due 2019 — 250.0 2.500% 2013 Series A due 2023 400.0 400.0 4.300% 2014 Series A due 2044 475.0 475.0 4.150% 2015 Series A due 2045 350.0 350.0 3.200% 2017 Series A due 2027 500.0 300.0 4.000% 2018 Series A due 2048 800.0 500.0 Total First Mortgage Bonds 3,394.8 3,144.8 Pollution Control Revenue Bonds: 4.375% Fixed Rate Tax Exempt due 2028 120.5 120.5 Less Amounts due Within One Year — (250.0 ) Unamortized Premiums and Discounts, Net 27.8 10.2 Unamortized Debt Issuance Costs (25.0 ) (21.5 ) CL&P Long-Term Debt $ 3,518.1 $ 3,004.0 NSTAR Electric (Millions of Dollars) As of December 31, 2019 2018 Debentures: 5.750% due 2036 $ 200.0 $ 200.0 5.500% due 2040 300.0 300.0 2.375% due 2022 400.0 400.0 4.400% due 2044 300.0 300.0 3.250% due 2025 250.0 250.0 2.700% due 2026 250.0 250.0 3.200% due 2027 700.0 700.0 3.250% due 2029 400.0 — Total Debentures 2,800.0 2,400.0 Notes: 5.900% Senior Notes Series B due 2034 50.0 50.0 6.700% Senior Notes Series D due 2037 40.0 40.0 5.100% Senior Notes Series E due 2020 95.0 95.0 3.500% Senior Notes Series F due 2021 250.0 250.0 3.880% Senior Notes Series G due 2023 80.0 80.0 2.750% Senior Notes Series H due 2026 50.0 50.0 Total Notes 565.0 565.0 Less Amounts due Within One Year (95.0 ) — Unamortized Premiums and Discounts, Net (4.1 ) (2.5 ) Unamortized Debt Issuance Costs (18.8 ) (17.7 ) NSTAR Electric Long-Term Debt $ 3,247.1 $ 2,944.8 PSNH (Millions of Dollars) As of December 31, 2019 2018 First Mortgage Bonds: 5.600% Series M due 2035 $ 50.0 $ 50.0 4.500% Series P due 2019 — 150.0 4.050% Series Q due 2021 122.0 122.0 3.200% Series R due 2021 160.0 160.0 3.500% Series S due 2023 325.0 325.0 3.600% Series T due 2049 300.0 — Total First Mortgage Bonds 957.0 807.0 Less Amounts due Within One Year — (150.0 ) Unamortized Premiums and Discounts, Net (0.7 ) — Unamortized Debt Issuance Costs (4.7 ) (1.8 ) PSNH Long-Term Debt $ 951.6 $ 655.2 OTHER (Millions of Dollars) As of December 31, 2019 2018 Yankee Gas - First Mortgage Bonds: 2.230% - 8.480% due 2020 - 2049 $ 620.0 $ 470.0 NSTAR Gas - First Mortgage Bonds: 3.740% - 9.950% due 2020 - 2049 460.0 385.0 Aquarion - Senior Note 4.000% due 2024 360.0 360.0 Aquarion - Unsecured Notes 0% - 6.430% due 2021 - 2049 335.3 289.5 Aquarion - Secured Debt 4.100% - 9.640% due 2021 - 2035 68.8 70.7 Eversource Parent - Debentures 4.500% due 2019 — 350.0 Eversource Parent - Senior Notes 2.500% - 4.250% due 2021 - 2029 4,000.0 4,000.0 Pre-1983 Spent Nuclear Fuel Obligation (CYAPC) 11.6 39.5 Fair Value Adjustment (1) 109.1 144.7 Less Fair Value Adjustment - Current Portion (1) (31.3 ) (36.2 ) Less Amounts due in One Year (201.1 ) (401.1 ) Commercial Paper Classified as Long-Term Debt (See Note 8, Short-Term Debt) 346.3 — Unamortized Premiums and Discounts, Net (4.1 ) (4.2 ) Unamortized Debt Issuance Costs (20.6 ) (23.2 ) Total Other Long-Term Debt $ 6,054.0 $ 5,644.7 Total Eversource Long-Term Debt $ 13,770.8 $ 12,248.7 (1) The fair value adjustment amount is the purchase price adjustments, net of amortization, required to record long-term debt at fair value on the dates of the 2012 merger with NSTAR and the 2017 acquisition of Aquarion.

LONG-TERM DEBT (Tables)

LONG-TERM DEBT (Tables)	12 Months Ended
LONG-TERM DEBT (Tables)	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Outstanding Long-Term Debt	The amount of borrowings outstanding and available under the commercial paper programs were as follows: Borrowings Outstanding as of December 31, Available Borrowing Capacity as of December 31, Weighted-Average Interest Rate as of December 31, (Millions of Dollars) 2019 2018 2019 2018 2019 2018 Eversource Parent Commercial Paper Program $ 1,224.9 $ 631.5 $ 225.1 $ 818.5 1.98 % 2.77 % NSTAR Electric Commercial Paper Program 10.5 278.5 639.5 371.5 1.63 % 2.50 % Details of long-term debt outstanding are as follows: CL&P (Millions of Dollars) As of December 31, 2019 2018 First Mortgage Bonds: 7.875% 1994 Series D due 2024 $ 139.8 $ 139.8 5.750% 2004 Series B due 2034 130.0 130.0 5.625% 2005 Series B due 2035 100.0 100.0 6.350% 2006 Series A due 2036 250.0 250.0 5.750% 2007 Series B due 2037 150.0 150.0 6.375% 2007 Series D due 2037 100.0 100.0 5.500% 2009 Series A due 2019 — 250.0 2.500% 2013 Series A due 2023 400.0 400.0 4.300% 2014 Series A due 2044 475.0 475.0 4.150% 2015 Series A due 2045 350.0 350.0 3.200% 2017 Series A due 2027 500.0 300.0 4.000% 2018 Series A due 2048 800.0 500.0 Total First Mortgage Bonds 3,394.8 3,144.8 Pollution Control Revenue Bonds: 4.375% Fixed Rate Tax Exempt due 2028 120.5 120.5 Less Amounts due Within One Year — (250.0 ) Unamortized Premiums and Discounts, Net 27.8 10.2 Unamortized Debt Issuance Costs (25.0 ) (21.5 ) CL&P Long-Term Debt $ 3,518.1 $ 3,004.0 NSTAR Electric (Millions of Dollars) As of December 31, 2019 2018 Debentures: 5.750% due 2036 $ 200.0 $ 200.0 5.500% due 2040 300.0 300.0 2.375% due 2022 400.0 400.0 4.400% due 2044 300.0 300.0 3.250% due 2025 250.0 250.0 2.700% due 2026 250.0 250.0 3.200% due 2027 700.0 700.0 3.250% due 2029 400.0 — Total Debentures 2,800.0 2,400.0 Notes: 5.900% Senior Notes Series B due 2034 50.0 50.0 6.700% Senior Notes Series D due 2037 40.0 40.0 5.100% Senior Notes Series E due 2020 95.0 95.0 3.500% Senior Notes Series F due 2021 250.0 250.0 3.880% Senior Notes Series G due 2023 80.0 80.0 2.750% Senior Notes Series H due 2026 50.0 50.0 Total Notes 565.0 565.0 Less Amounts due Within One Year (95.0 ) — Unamortized Premiums and Discounts, Net (4.1 ) (2.5 ) Unamortized Debt Issuance Costs (18.8 ) (17.7 ) NSTAR Electric Long-Term Debt $ 3,247.1 $ 2,944.8 PSNH (Millions of Dollars) As of December 31, 2019 2018 First Mortgage Bonds: 5.600% Series M due 2035 $ 50.0 $ 50.0 4.500% Series P due 2019 — 150.0 4.050% Series Q due 2021 122.0 122.0 3.200% Series R due 2021 160.0 160.0 3.500% Series S due 2023 325.0 325.0 3.600% Series T due 2049 300.0 — Total First Mortgage Bonds 957.0 807.0 Less Amounts due Within One Year — (150.0 ) Unamortized Premiums and Discounts, Net (0.7 ) — Unamortized Debt Issuance Costs (4.7 ) (1.8 ) PSNH Long-Term Debt $ 951.6 $ 655.2 OTHER (Millions of Dollars) As of December 31, 2019 2018 Yankee Gas - First Mortgage Bonds: 2.230% - 8.480% due 2020 - 2049 $ 620.0 $ 470.0 NSTAR Gas - First Mortgage Bonds: 3.740% - 9.950% due 2020 - 2049 460.0 385.0 Aquarion - Senior Note 4.000% due 2024 360.0 360.0 Aquarion - Unsecured Notes 0% - 6.430% due 2021 - 2049 335.3 289.5 Aquarion - Secured Debt 4.100% - 9.640% due 2021 - 2035 68.8 70.7 Eversource Parent - Debentures 4.500% due 2019 — 350.0 Eversource Parent - Senior Notes 2.500% - 4.250% due 2021 - 2029 4,000.0 4,000.0 Pre-1983 Spent Nuclear Fuel Obligation (CYAPC) 11.6 39.5 Fair Value Adjustment (1) 109.1 144.7 Less Fair Value Adjustment - Current Portion (1) (31.3 ) (36.2 ) Less Amounts due in One Year (201.1 ) (401.1 ) Commercial Paper Classified as Long-Term Debt (See Note 8, Short-Term Debt) 346.3 — Unamortized Premiums and Discounts, Net (4.1 ) (4.2 ) Unamortized Debt Issuance Costs (20.6 ) (23.2 ) Total Other Long-Term Debt $ 6,054.0 $ 5,644.7 Total Eversource Long-Term Debt $ 13,770.8 $ 12,248.7 (1) The fair value adjustment amount is the purchase price adjustments, net of amortization, required to record long-term debt at fair value on the dates of the 2012 merger with NSTAR and the 2017 acquisition of Aquarion.
Schedule of Issuance and Repayments of Long-term Debt	The following table summarizes long-term debt issuances and repayments: (Millions of Dollars) Issue Date Issuance/(Repayment) Maturity Date Use of Proceeds for Issuance/ CL&P: 4.00% 2018 Series A First Mortgage Bonds (1) April 2019 $ 300.0 April 2048 Paid short-term borrowings that were used to pay long-term debt that matured on February 1, 2019 and fund capital expenditures and working capital 3.20% 2017 Series A First Mortgage Bonds (2) September 2019 200.0 March 2027 Paid short-term borrowings and fund capital expenditures and working capital 5.50% 2009 Series A First Mortgage Bonds February 2009 (250.0 ) February 2019 Paid at maturity on February 1, 2019 NSTAR Electric: 3.25% 2019 Debentures May 2019 400.0 May 2029 Paid short-term borrowings that were used to fund investments in eligible green expenditures PSNH: 3.60% 2019 Series T First Mortgage Bonds June 2019 300.0 July 2049 Paid long-term debt that matured in December 2019, paid short-term borrowings and fund capital expenditures and working capital 4.50% 2009 Series P First Mortgage Bonds December 2009 (150.0 ) December 2019 Paid at maturity on December 1, 2019 Other: Eversource Parent 4.50% Debentures November 2009 (350.0 ) November 2019 Paid at maturity on November 15, 2019 Eversource Parent 3.45% Series P Senior Notes January 2020 350.0 January 2050 Paid short-term borrowings NSTAR Gas 3.74% Series Q First Mortgage Bonds July 2019 75.0 August 2049 Paid short-term borrowings and fund capital expenditures and working capital Yankee Gas 2.23% Series P First Mortgage Bonds September 2019 100.0 October 2024 Paid short-term borrowings and for general corporate purposes Yankee Gas 3.30% Series Q First Mortgage Bonds September 2019 100.0 October 2049 Paid short-term borrowings and for general corporate purposes Yankee Gas 5.26% Series H First Mortgage Bonds November 2004 (50.0 ) November 2019 Paid at maturity on November 1, 2019 Aquarion 3.54% Senior Notes December 2019 45.0 December 2049 Paid short-term borrowings (1) These bonds are part of the same series issued by CL&P in March 2018. The aggregate outstanding principal amount of these bonds is now $800 million . (2) These bonds are part of the same series issued by CL&P in March 2017. The aggregate outstanding principal amount of these bonds is now $500 million .
Schedule of Maturities of Long-term Debt Outstanding	Long-term debt maturities on debt outstanding for the years 2020 through 2024 and thereafter are shown below. These amounts exclude PSNH rate reduction bonds, CYAPC pre-1983 spent nuclear fuel obligation, net unamortized premiums, discounts and debt issuance costs, and other fair value adjustments as of December 31, 2019 : (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2020 $ 296.1 $ — $ 95.0 $ — 2021 1,033.6 — 250.0 282.0 2022 1,188.9 — 400.0 — 2023 1,665.2 400.0 80.0 325.0 2024 1,049.8 139.8 — — Thereafter 8,447.8 2,975.5 2,540.0 350.0 Total $ 13,681.4 $ 3,515.3 $ 3,365.0 $ 957.0

RATE REDUCTION BONDS AND VARI_2

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES (Tables)	12 Months Ended
	Dec. 31, 2019
Rate Reduction Bonds and Variable Interest Entity [Abstract]
Summary of the Impact of Funding on the Balance Sheets and Income Statements	The following tables summarize the impact of PSNH Funding on PSNH's balance sheets and income statements: (Millions of Dollars) Balance Sheet: As of December 31, 2019 As of December 31, 2018 Restricted Cash - Current Portion (included in Current Assets) $ 32.5 $ 47.5 Restricted Cash - Long-Term Portion (included in Other Long-Term Assets) 3.2 3.2 Securitized Stranded Cost (included in Regulatory Assets) 565.3 608.4 Other Regulatory Liabilities (included in Regulatory Liabilities) 5.6 5.8 Accrued Interest (included in Other Current Liabilities) 8.6 14.4 Rate Reduction Bonds - Current Portion 43.2 52.3 Rate Reduction Bonds - Long-Term Portion 540.1 583.3 (Millions of Dollars) Income Statement: For the Year Ended December 31, 2019 For the Year Ended December 31, 2018 Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net) $ 43.0 $ 27.3 Interest Expense on RRB Principal (included in Interest Expense) 21.1 14.4

EMPLOYEE BENEFITS (Tables)

EMPLOYEE BENEFITS (Tables)	12 Months Ended
EMPLOYEE BENEFITS (Tables)	Dec. 31, 2019
Postemployment Benefits [Abstract]
Schedule of Benefit Obligations in Excess of Fair Value of Plan Assets	PBOP As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Change in Benefit Obligation: Benefit Obligation as of Beginning of Year $ (841.5 ) $ (161.7 ) $ (246.3 ) $ (91.9 ) $ (948.6 ) $ (178.4 ) $ (278.6 ) $ (101.1 ) Service Cost (7.8 ) (1.4 ) (1.7 ) (0.7 ) (10.0 ) (1.9 ) (2.0 ) (1.1 ) Interest Cost (32.7 ) (6.3 ) (9.5 ) (3.4 ) (30.7 ) (5.8 ) (8.7 ) (3.4 ) Actuarial Gain/(Loss) (67.0 ) (13.4 ) (15.2 ) (3.1 ) 102.5 14.4 28.4 8.6 Benefits Paid 50.0 10.8 15.4 5.6 45.3 10.1 14.5 4.9 Employee Transfers — (0.7 ) (1.0 ) 0.5 — (0.1 ) 0.1 0.2 Benefit Obligation as of End of Year $ (899.0 ) $ (172.7 ) $ (258.3 ) $ (93.0 ) $ (841.5 ) $ (161.7 ) $ (246.3 ) $ (91.9 ) Change in Plan Assets: Fair Value of Plan Assets as of Beginning of Year $ 849.6 $ 120.6 $ 379.1 $ 71.2 $ 922.2 $ 135.9 $ 405.5 $ 79.0 Actual Return on Plan Assets 127.0 17.1 57.0 10.0 (36.6 ) (5.2 ) (17.4 ) (2.9 ) Employer Contributions 9.3 — 6.0 — 9.3 — 5.2 — Benefits Paid (50.0 ) (10.8 ) (15.4 ) (5.6 ) (45.3 ) (10.1 ) (14.5 ) (4.9 ) Employee Transfers — (0.6 ) (2.3 ) 0.4 — — 0.3 — Fair Value of Plan Assets as of End of Year $ 935.9 $ 126.3 $ 424.4 $ 76.0 $ 849.6 $ 120.6 $ 379.1 $ 71.2 Funded Status as of December 31st $ 36.9 $ (46.4 ) $ 166.1 $ (17.0 ) $ 8.1 $ (41.1 ) $ 132.8 $ (20.7 ) Pension and SERP As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Change in Benefit Obligation: Benefit Obligation as of Beginning of Year $ (5,520.0 ) $ (1,160.4 ) $ (1,236.5 ) $ (610.7 ) $ (5,936.5 ) $ (1,275.2 ) $ (1,351.0 ) $ (642.2 ) Service Cost (67.7 ) (18.0 ) (14.6 ) (7.1 ) (84.8 ) (21.4 ) (17.4 ) (11.2 ) Interest Cost (219.0 ) (45.7 ) (49.0 ) (24.0 ) (196.4 ) (41.8 ) (43.5 ) (22.0 ) Actuarial Gain/(Loss) (815.3 ) (176.6 ) (181.0 ) (84.5 ) 414.9 106.1 98.6 39.2 Benefits Paid - Pension 273.0 60.2 67.1 30.3 261.8 59.6 66.9 26.2 Benefits Paid - Lump Sum 20.0 — 12.9 — 14.2 — 7.1 — Benefits Paid - SERP 7.3 0.3 0.1 0.4 6.8 0.3 0.3 0.2 Employee Transfers — 8.9 3.7 3.0 — 12.0 2.5 (0.9 ) Benefit Obligation as of End of Year $ (6,321.7 ) $ (1,331.3 ) $ (1,397.3 ) $ (692.6 ) $ (5,520.0 ) $ (1,160.4 ) $ (1,236.5 ) $ (610.7 ) Change in Pension Plan Assets: Fair Value of Pension Plan Assets as of Beginning of Year $ 4,573.9 $ 918.4 $ 1,222.1 $ 506.6 $ 4,739.5 $ 963.0 $ 1,260.8 $ 539.5 Employer Contributions 112.5 24.0 0.4 15.4 185.6 41.2 56.5 — Actual Return on Pension Plan Assets 575.2 112.9 150.0 62.9 (75.2 ) (14.2 ) (18.7 ) (7.6 ) Benefits Paid - Pension (273.0 ) (60.2 ) (67.1 ) (30.3 ) (261.8 ) (59.6 ) (66.9 ) (26.2 ) Benefits Paid - Lump Sum (20.0 ) — (12.9 ) — (14.2 ) — (7.1 ) — Employee Transfers — (8.9 ) (3.7 ) (3.0 ) — (12.0 ) (2.5 ) 0.9 Fair Value of Pension Plan Assets as of End of Year $ 4,968.6 $ 986.2 $ 1,288.8 $ 551.6 $ 4,573.9 $ 918.4 $ 1,222.1 $ 506.6 Funded Status as of December 31st $ (1,353.1 ) $ (345.1 ) $ (108.5 ) $ (141.0 ) $ (946.1 ) $ (242.0 ) $ (14.4 ) $ (104.1 )
Schedule of Defined Benefit Plans	As of December 31, 2019 and 2018 , the accumulated benefit obligation for the Pension and SERP Plans is as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 5,963.4 $ 1,205.4 $ 1,340.8 $ 646.7 2018 5,070.8 1,031.0 1,144.7 543.1
Schedule of Assumptions Used	The following actuarial assumptions were used in calculating the Pension, SERP and PBOP Plans' year end funded status: Pension and SERP PBOP As of December 31, As of December 31, 2019 2018 2019 2018 Discount Rate 3.04% — 3.35% 4.22% — 4.45% 3.26% — 3.28% 4.38% — 4.41% Compensation/Progression Rate 3.50% — 4.00% 3.50% — 4.00% N/A The following actuarial assumptions were used to calculate Pension, SERP and PBOP expense amounts: Pension and SERP PBOP For the Years Ended December 31, For the Years Ended December 31, 2019 2018 2017 2019 2018 2017 Discount Rate 2.63% — 3.55% 3.85% — 4.62% 3.20% — 3.90% 3.85% — 4.65% 3.28% — 3.94% 3.48% — 4.64% Expected Long-Term Rate of Return 8.25% 8.25% 8.25% 8.25% 8.25% 8.25% Compensation/Progression Rate 3.50% — 4.00% 3.50% — 4.00% 3.50% N/A N/A N/A
Schedule of Net Benefit Costs	The components of net periodic benefit expense/(income) for the Pension, SERP and PBOP Plans, prior to amounts capitalized as Property, Plant and Equipment or deferred as regulatory assets for future recovery, are shown below. The service cost component of net periodic benefit expense/(income), less the capitalized portion, is included in Operations and Maintenance expense on the statements of income. The remaining components of net periodic benefit expense/(income), less the deferred portion, are included in Other Income, Net on the statements of income. Pension, SERP and PBOP expense reflected in the statements of cash flows for CL&P, NSTAR Electric and PSNH does not include the intercompany allocations or the corresponding capitalized and deferred portion, as these amounts are cash settled on a short-term basis. Pension and SERP PBOP For the Year Ended December 31, 2019 For the Year Ended December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 67.7 $ 18.0 $ 14.6 $ 7.1 $ 7.8 $ 1.4 $ 1.7 $ 0.7 Interest Cost 219.0 45.7 49.0 24.0 32.7 6.3 9.5 3.4 Expected Return on Plan Assets (367.1 ) (73.2 ) (97.1 ) (40.7 ) (66.8 ) (9.2 ) (30.2 ) (5.4 ) Actuarial Loss 143.2 26.9 44.7 10.6 8.3 1.3 3.3 0.3 Prior Service Cost/(Credit) 0.9 — 0.3 — (23.5 ) 1.1 (16.9 ) 0.4 Total Net Periodic Benefit Expense/(Income) $ 63.7 $ 17.4 $ 11.5 $ 1.0 $ (41.5 ) $ 0.9 $ (32.6 ) $ (0.6 ) Intercompany Allocations N/A $ 8.5 $ 8.0 $ 2.3 N/A $ (0.9 ) $ (1.2 ) $ (0.4 ) Pension and SERP PBOP For the Year Ended December 31, 2018 For the Year Ended December 31, 2018 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 84.8 $ 21.4 $ 17.4 $ 11.2 $ 10.0 $ 1.9 $ 2.0 $ 1.1 Interest Cost 196.4 41.8 43.5 22.0 30.7 5.8 8.7 3.4 Expected Return on Plan Assets (391.6 ) (79.1 ) (104.9 ) (43.6 ) (72.4 ) (10.4 ) (32.5 ) (6.0 ) Actuarial Loss 145.7 29.1 41.1 11.6 10.3 1.6 2.3 0.7 Prior Service Cost/(Credit) 4.3 1.1 0.2 0.4 (23.6 ) 1.1 (16.9 ) 0.5 Total Net Periodic Benefit Expense/(Income) $ 39.6 $ 14.3 $ (2.7 ) $ 1.6 $ (45.0 ) $ — $ (36.4 ) $ (0.3 ) Intercompany Allocations N/A $ 6.1 $ 6.5 $ 1.9 N/A $ (1.0 ) $ (1.3 ) $ (0.4 ) Pension and SERP PBOP For the Year Ended December 31, 2017 For the Year Ended December 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 71.3 $ 18.5 $ 15.5 $ 9.7 $ 9.5 $ 1.9 $ 1.7 $ 1.3 Interest Cost 188.0 41.6 42.7 21.2 27.1 5.3 8.7 3.0 Expected Return on Plan Assets (334.1 ) (71.7 ) (87.6 ) (40.0 ) (63.7 ) (9.7 ) (28.6 ) (5.5 ) Actuarial Loss 135.2 27.7 41.1 11.6 9.1 1.0 3.4 0.6 Prior Service Cost/(Credit) 4.5 1.5 0.6 0.5 (21.6 ) 1.1 (17.0 ) 0.6 Total Net Periodic Benefit Expense/(Income) $ 64.9 $ 17.6 $ 12.3 $ 3.0 $ (39.6 ) $ (0.4 ) $ (31.8 ) $ — Intercompany Allocations N/A $ 9.8 $ 9.1 $ 3.3 N/A $ (0.7 ) $ (1.1 ) $ (0.5 )
Schedule of Amounts Recognized in Regulatory Assets and OCI	The following is a summary of the changes in plan assets and benefit obligations recognized in Regulatory Assets and Other Comprehensive Income (OCI) as well as amounts in Regulatory Assets and OCI that were reclassified as net periodic benefit expense during the years presented: Pension and SERP PBOP Regulatory Assets OCI Regulatory Assets OCI For the Years Ended December 31, For the Years Ended December 31, (Millions of Dollars) 2019 2018 2019 2018 2019 2018 2019 2018 Actuarial Losses/(Gains) Arising During the Year $ 591.6 $ 48.6 $ 15.4 $ 0.7 $ 4.6 $ 6.4 $ 2.3 $ (1.2 ) Actuarial Losses Reclassified as Net Periodic Benefit Expense (137.8 ) (140.1 ) (5.4 ) (5.6 ) (8.0 ) (9.9 ) (0.3 ) (0.4 ) Actuarial Losses Securitized as Stranded Costs (1) — (36.7 ) — — — (0.8 ) — — Prior Service Cost Arising During the Year — — — — — 1.3 — — Prior Service (Cost)/Credit Reclassified as Net Periodic Benefit (Expense)/Income (0.7 ) (3.9 ) (0.2 ) (0.4 ) 25.1 23.6 (1.6 ) — Prior Service Cost Securitized as Stranded Costs (1) — (0.1 ) — — — (1.3 ) — — (1) These amounts were reclassified to securitized regulatory assets in connection with the divestiture of PSNH's generation business. For further information see Note 2, "Regulatory Accounting" to the financial statements. The following is a summary of the remaining Regulatory Assets and Accumulated Other Comprehensive Income amounts that have not been recognized as components of net periodic benefit expense as of December 31, 2019 and 2018 , as well as the amounts that are expected to be recognized as components in 2020 : Regulatory Assets as of December 31, Expected 2020 Expense/(Income) AOCI as of December 31, Expected 2020 Expense (Millions of Dollars) 2019 2018 2019 2018 Pension and SERP Actuarial Loss $ 2,261.4 $ 1,807.6 $ 190.3 $ 90.8 $ 80.8 $ 7.2 Prior Service Cost 5.6 6.3 0.9 0.9 1.1 0.2 PBOP Actuarial Loss $ 203.9 $ 207.3 $ 8.3 $ 7.0 $ 5.0 $ 0.2 Prior Service (Credit)/Cost (172.5 ) (197.6 ) (21.4 ) 1.0 2.6 0.2
Schedule of Expected Benefit Payments	The following benefit payments, which reflect expected future service, are expected to be paid by the Pension, SERP and PBOP Plans: (Millions of Dollars) 2020 2021 2022 2023 2024 2025 - 2029 Pension and SERP $ 320.1 $ 328.7 $ 337.5 $ 346.5 $ 352.4 $ 1,813.1 PBOP 58.1 57.9 57.3 56.8 56.2 264.7
Schedule of Allocation of Plan Assets	The following table presents, by asset category, the Pension and PBOP Plan assets recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Pension Plan Fair Value Measurements as of December 31, (Millions of Dollars) 2019 2018 Asset Category: Level 1 Level 2 Uncategorized Total Level 1 Level 2 Uncategorized Total Equity Securities (1) $ 592.6 $ — $ 1,349.9 $ 1,942.5 $ 443.4 $ — $ 1,377.8 $ 1,821.2 Fixed Income (2) 99.4 303.0 1,222.8 1,625.2 85.5 160.8 1,265.5 1,511.8 Private Equity 16.9 — 971.4 988.3 6.1 — 834.0 840.1 Real Assets (3) 58.7 — 615.0 673.7 62.9 — 569.1 632.0 Total $ 767.6 $ 303.0 $ 4,159.1 $ 5,229.7 $ 597.9 $ 160.8 $ 4,046.4 $ 4,805.1 Less: 401(h) PBOP Assets (4) (261.1 ) (231.2 ) Total Pension Assets $ 4,968.6 $ 4,573.9 PBOP Plan Fair Value Measurements as of December 31, (Millions of Dollars) 2019 2018 Asset Category: Level 1 Level 2 Uncategorized Total Level 1 Level 2 Uncategorized Total Equity Securities (1) $ 158.0 $ — $ 187.0 $ 345.0 $ 91.9 $ — $ 210.5 $ 302.4 Fixed Income (2) 15.8 39.6 148.1 203.5 22.0 40.3 123.0 185.3 Private Equity — — 26.5 26.5 — — 32.7 32.7 Real Assets (3) 51.2 — 48.6 99.8 27.5 — 70.5 98.0 Total $ 225.0 $ 39.6 $ 410.2 $ 674.8 $ 141.4 $ 40.3 $ 436.7 $ 618.4 Add: 401(h) PBOP Assets (4) 261.1 231.2 Total PBOP Assets $ 935.9 $ 849.6 (1) United States, Global, Non-United States and Emerging Markets equity securities that are uncategorized include investments in commingled funds and hedge funds that are overlaid with equity index swaps and futures contracts. (2) Fixed Income investments that are uncategorized include investments in commingled funds, fixed income funds that invest in a variety of opportunistic and fixed income strategies, and hedge funds that are overlaid with fixed income futures. (3) Real assets include real estate funds and hedge funds. (4) The assets of the Pension Plan include a 401(h) account that has been allocated to provide health and welfare postretirement benefits under the PBOP Plan. These long-term rates of return are based on the assumed rates of return for the target asset allocations as follows: As of December 31, 2019 2018 Eversource Pension Plan and Tax-Exempt Assets Within PBOP Plan Eversource Pension Plan and Tax-Exempt Assets Within PBOP Plan Target Asset Allocation Assumed Rate of Return Target Asset Allocation Assumed Rate of Return Equity Securities: United States 15.0 % 8.5 % 15.0 % 8.5 % Global 10.0 % 8.75 % 10.0 % 8.75 % Non-United States 8.0 % 8.5 % 8.0 % 8.5 % Emerging Markets 4.0 % 10.0 % 4.0 % 10.0 % Debt Securities: Fixed Income 13.0 % 4.0 % 13.0 % 4.0 % Public High Yield Fixed Income 4.0 % 6.5 % 4.0 % 6.5 % Private Debt 15.0 % 9.0 % 15.0 % 9.0 % Private Equity 15.0 % 12.0 % 15.0 % 12.0 % Real Assets 16.0 % 7.5 % 16.0 % 7.5 %
Schedule of Defined Contribution Plans	The total Eversource 401k Plan employer matching contributions, including the K-Vantage contributions, were as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 41.6 $ 5.5 $ 10.3 $ 3.5 2018 38.4 5.0 9.7 3.3 2017 34.5 4.6 8.5 3.7
Schedule of Other Retirement Benefits	The liability and expense amounts are as follows: Eversource (Millions of Dollars) As of and For the Years Ended December 31, 2019 2018 2017 Actuarially-Determined Liability $ 52.0 $ 49.1 $ 53.4 Other Retirement Benefits Expense 2.7 2.7 2.8 As of and For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Actuarially-Determined Liability $ 0.2 $ 0.1 $ 1.7 $ 0.3 $ 0.1 $ 1.7 $ 0.3 $ 0.1 $ 1.9 Other Retirement Benefits Expense 1.0 0.9 0.4 1.1 1.1 0.4 1.0 1.0 0.5
Summary of Share Transactions	A summary of performance share transactions is as follows: Performance Shares (Units) Weighted Average Grant-Date Fair Value Outstanding as of December 31, 2018 499,564 $ 56.08 Granted 165,022 $ 68.33 Shares Issued (162,959 ) $ 55.69 Forfeited (14,720 ) $ 58.20 Outstanding as of December 31, 2019 486,907 $ 60.30 RSUs (Units) Weighted Average Grant-Date Fair Value Outstanding as of December 31, 2018 782,365 $ 50.25 Granted 271,144 $ 67.91 Shares Issued (263,219 ) $ 55.34 Forfeited (16,127 ) $ 63.31 Outstanding as of December 31, 2019 774,163 $ 54.43
Schedule of Compensation Expense and Income Tax Benefit	The total compensation expense and associated future income tax benefits recognized by Eversource, CL&P, NSTAR Electric and PSNH for share-based compensation awards were as follows: Eversource For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Compensation Expense $ 27.3 $ 21.4 $ 19.7 Future Income Tax Benefit 7.0 5.4 8.0 For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Compensation Expense $ 9.8 $ 9.7 $ 3.3 $ 7.8 $ 7.7 $ 2.9 $ 7.0 $ 7.0 $ 3.2 Future Income Tax Benefit 2.5 2.5 0.8 2.0 1.9 0.7 2.9 2.8 1.3

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
INCOME TAXES (Tables)	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Components of Income Tax Expense	The components of income tax expense are as follows: Eversource (Millions of Dollars) For the Years Ended December 31, 2019 2018 2017 Current Income Taxes: Federal $ 56.9 $ 106.5 $ 58.9 State 10.5 10.6 31.6 Total Current 67.4 117.1 90.5 Deferred Income Taxes, Net: Federal 138.4 122.6 433.0 State 71.4 52.2 58.6 Total Deferred 209.8 174.8 491.6 Investment Tax Credits, Net (3.7 ) (2.9 ) (3.2 ) Income Tax Expense $ 273.5 $ 289.0 $ 578.9 For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR PSNH CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Current Income Taxes: Federal $ 68.4 $ 82.6 $ 22.9 $ 54.2 $ 79.3 $ 12.2 $ 50.9 $ 107.8 $ 18.6 State 15.4 18.2 2.2 20.9 30.0 (0.5 ) 17.4 25.6 6.2 Total Current 83.8 100.8 25.1 75.1 109.3 11.7 68.3 133.4 24.8 Deferred Income Taxes, Net: Federal 35.2 0.1 5.8 48.5 27.9 15.4 123.9 88.1 52.7 State 18.8 27.0 10.1 6.4 13.5 20.5 (4.6 ) 22.4 11.2 Total Deferred 54.0 27.1 15.9 54.9 41.4 35.9 119.3 110.5 63.9 Investment Tax Credits, Net (0.8 ) (2.6 ) — (0.9 ) (1.8 ) — (1.0 ) (1.8 ) — Income Tax Expense $ 137.0 $ 125.3 $ 41.0 $ 129.1 $ 148.9 $ 47.6 $ 186.6 $ 242.1 $ 88.7
Summary of Reconciliation Between Income Tax Expense and Expected Tax	A reconciliation between income tax expense and the expected tax expense at the statutory rate is as follows: Eversource (Millions of Dollars, except percentages) For the Years Ended December 31, 2019 2018 2017 Income Before Income Tax Expense $ 1,190.1 $ 1,329.5 $ 1,574.4 Statutory Federal Income Tax Expense at 21% in 2019 and 2018, and 35% in 2017 249.9 279.2 551.0 Tax Effect of Differences: Depreciation 1.9 (30.8 ) (10.8 ) Investment Tax Credit Amortization (3.7 ) (2.9 ) (3.2 ) State Income Taxes, Net of Federal Impact 24.6 44.4 47.7 Dividends on ESOP (5.1 ) (5.1 ) (8.4 ) Tax Asset Valuation Allowance/Reserve Adjustments 40.1 5.2 7.0 Excess Stock Benefit (1.5 ) (1.5 ) (2.9 ) EDIT Amortization (37.4 ) (5.0 ) — Other, Net 4.7 5.5 (1.5 ) Income Tax Expense $ 273.5 $ 289.0 $ 578.9 Effective Tax Rate 23.0 % 21.7 % 36.8 % For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars, except percentages) CL&P NSTAR PSNH CL&P NSTAR PSNH CL&P NSTAR PSNH Income Before Income Tax Expense $ 547.8 $ 557.3 $ 175.0 $ 506.8 $ 532.0 $ 163.5 $ 563.4 $ 616.8 $ 224.7 Statutory Federal Income Tax Expense at 21% in 2019 and 2018, and 35% in 2017 115.0 117.0 36.8 106.4 111.7 34.3 197.2 215.9 78.6 Tax Effect of Differences: Depreciation (0.2 ) (3.0 ) (0.8 ) (1.2 ) (2.8 ) 0.1 (5.2 ) (3.0 ) 1.1 Investment Tax Credit Amortization (0.8 ) (2.6 ) — (0.9 ) (1.8 ) — (1.0 ) (1.8 ) — State Income Taxes, Net of Federal Impact 2.5 35.7 9.8 14.5 33.2 15.8 4.5 31.2 11.3 Tax Asset Valuation Allowance/Reserve Adjustments 24.5 — — 7.1 1.2 — (9.5 ) — — Excess Stock Benefit (0.5 ) (0.5 ) (0.2 ) (0.1 ) (0.1 ) (0.1 ) (0.7 ) (0.7 ) (0.3 ) EDIT Amortization (5.8 ) (22.9 ) (4.0 ) — — (4.4 ) — — — Other, Net 2.3 1.6 (0.6 ) 3.3 7.5 1.9 1.3 0.5 (2.0 ) Income Tax Expense $ 137.0 $ 125.3 $ 41.0 $ 129.1 $ 148.9 $ 47.6 $ 186.6 $ 242.1 $ 88.7 Effective Tax Rate 25.0 % 22.5 % 23.4 % 25.5 % 28.0 % 29.1 % 33.1 % 39.2 % 39.5 %
Schedule of Accumulated Deferred Income Tax Obligations	The tax effects of temporary differences that give rise to the net accumulated deferred income tax obligations are as follows: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Deferred Tax Assets: Employee Benefits $ 509.4 $ 125.4 $ 54.8 $ 46.7 $ 388.2 $ 94.5 $ 35.0 $ 31.1 Derivative Liabilities 105.0 103.6 — — 111.4 111.4 — — Regulatory Deferrals - Liabilities 267.0 37.1 165.7 19.0 299.3 38.6 195.5 16.1 Allowance for Uncollectible Accounts 56.7 25.7 17.7 2.8 54.0 23.1 17.8 3.0 Tax Effect - Tax Regulatory Liabilities 830.4 333.5 280.9 111.3 830.3 336.8 288.9 111.7 Net Operating Loss Carryforwards 9.1 — — — 28.5 — — 0.6 Purchase Accounting Adjustment 58.7 — — — 64.2 — — — Other 190.4 92.0 35.8 20.0 166.2 81.1 15.6 33.4 Total Deferred Tax Assets 2,026.7 717.3 554.9 199.8 1,942.1 685.5 552.8 195.9 Less: Valuation Allowance 43.0 24.9 — — 19.5 10.7 — — Net Deferred Tax Assets $ 1,983.7 $ 692.4 $ 554.9 $ 199.8 $ 1,922.6 $ 674.8 $ 552.8 $ 195.9 Deferred Tax Liabilities: Accelerated Depreciation and Other Plant-Related Differences $ 3,901.0 $ 1,362.2 $ 1,391.9 $ 428.9 $ 3,724.2 $ 1,293.3 $ 1,342.4 $ 410.6 Property Tax Accruals 76.8 36.8 29.0 4.7 73.2 35.4 26.3 5.2 Regulatory Amounts: Regulatory Deferrals - Assets 1,155.6 340.7 276.2 260.9 1,025.9 320.1 277.4 213.8 Tax Effect - Tax Regulatory Assets 238.2 171.7 11.7 8.3 238.9 167.0 9.7 8.1 Goodwill Regulatory Asset - 1999 Merger 90.6 — 77.8 — 95.2 — 81.7 — Derivative Assets 19.7 19.7 — — 20.1 19.9 — — Other 257.6 5.9 125.6 3.2 251.1 5.9 109.8 39.4 Total Deferred Tax Liabilities $ 5,739.5 $ 1,937.0 $ 1,912.2 $ 706.0 $ 5,428.6 $ 1,841.6 $ 1,847.3 $ 677.1
Summary of Tax Credits and Loss Carryforwards	The following table provides the amounts and expiration dates of state tax credit and loss carryforwards and federal tax credit and net operating loss carryforwards: As of December 31, 2019 2018 (Millions of Dollars) Eversource CL&P NSTAR PSNH Expiration Range Eversource CL&P NSTAR PSNH Expiration Range Federal Net $ 19.8 $ — $ — $ — 2033 - 2037 $ 103.6 $ — $ — $ — 2033 - 2037 Federal Charitable — — — — 2020 - 2022 2.2 — — — 2020 - 2022 State Net Operating Loss 65.5 — — — 2020 - 2038 80.7 — — — 2019 - 2038 State Tax Credit 168.1 122.3 — — 2019 - 2024 148.9 107.0 — — 2018 - 2023 State Charitable 9.9 — — — 2019 - 2023 9.6 — — — 2019 - 2023
Summary of Income Tax Contingencies	The amount of interest expense/(income) on uncertain tax positions recognized and the related accrued interest payable/(receivable) are as follows: Other Interest Expense/(Income) Accrued Interest Expense For the Years Ended December 31, As of December 31, (Millions of Dollars) 2019 2018 2017 2019 2018 Eversource $ — $ (1.7 ) $ — $ 0.1 $ 0.1 A reconciliation of the activity in unrecognized tax benefits, all of which would impact the effective tax rate if recognized, is as follows: (Millions of Dollars) Eversource CL&P Balance as of January 1, 2017 $ 48.4 $ 15.3 Gross Increases - Current Year 11.4 4.7 Gross Decreases - Prior Year (0.9 ) (0.5 ) Lapse of Statute of Limitations (7.2 ) (1.4 ) Balance as of December 31, 2017 51.7 18.1 Gross Increases - Current Year 9.2 3.2 Gross Decreases - Prior Year (6.5 ) (0.9 ) Lapse of Statute of Limitations (8.5 ) (2.2 ) Balance as of December 31, 2018 45.9 18.2 Gross Increases - Current Year 12.1 4.0 Gross Increases - Prior Year 3.4 3.3 Lapse of Statute of Limitations (6.4 ) (2.4 ) Balance as of December 31, 2019 $ 55.0 $ 23.1
Summary of Income Tax Examinations	The following table summarizes Eversource, CL&P, NSTAR Electric and PSNH's tax years that remain subject to examination by major tax jurisdictions as of December 31, 2019 : Description Tax Years Federal 2019 Connecticut 2016 - 2019 Massachusetts 2016 - 2019 New Hampshire 2017 - 2019

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Tables)	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of Environmental Loss Contingencies by Site	A reconciliation of the activity in the environmental reserves is as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Balance as of January 1, 2018 $ 54.9 $ 4.7 $ 2.7 $ 5.7 Additions 23.5 1.9 9.7 — Payments/Reductions (13.7 ) (1.2 ) (1.5 ) (0.3 ) Balance as of December 31, 2018 64.7 5.4 10.9 5.4 Additions 26.5 7.0 0.5 2.8 Payments/Reductions (10.2 ) (1.0 ) (3.4 ) (0.7 ) Balance as of December 31, 2019 $ 81.0 $ 11.4 $ 8.0 $ 7.5 The number of environmental sites for which remediation or long-term monitoring, preliminary site work or site assessment is being performed are as follows: Eversource CL&P NSTAR Electric PSNH 2019 57 15 15 9 2018 60 15 16 9
Schedule of Estimated Future Annual Costs of Long term Contractual Agreement	The estimated future annual costs of significant executed, non-cancelable, long-term contractual arrangements in effect as of December 31, 2019 are as follows: Eversource (Millions of Dollars) 2020 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 614.6 $ 594.3 $ 651.7 $ 629.1 $ 624.8 $ 3,590.6 $ 6,705.1 Purchased Power and Capacity 73.5 69.0 75.1 81.6 75.9 71.5 446.6 Peaker CfDs 22.4 23.0 16.9 20.1 15.5 29.8 127.7 Natural Gas Procurement 266.2 255.3 202.8 166.7 165.7 1,093.3 2,150.0 Transmission Support Commitments 22.1 — — — — — 22.1 Total $ 998.8 $ 941.6 $ 946.5 $ 897.5 $ 881.9 $ 4,785.2 $ 9,451.5 CL&P (Millions of Dollars) 2020 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 457.3 $ 459.6 $ 514.4 $ 516.2 517.4 2,790.6 $ 5,255.5 Purchased Power and Capacity 69.8 65.3 71.4 78.0 72.9 55.5 412.9 Peaker CfDs 22.4 23.0 16.9 20.1 15.5 29.8 127.7 Transmission Support Commitments 8.7 — — — — — 8.7 Total $ 558.2 $ 547.9 $ 602.7 $ 614.3 $ 605.8 $ 2,875.9 $ 5,804.8 NSTAR Electric (Millions of Dollars) 2020 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 95.5 $ 91.2 $ 91.4 $ 66.6 $ 63.8 $ 418.1 $ 826.6 Purchased Power and Capacity 3.1 3.1 3.1 3.0 3.0 16.0 31.3 Transmission Support Commitments 8.7 — — — — — 8.7 Total $ 107.3 $ 94.3 $ 94.5 $ 69.6 $ 66.8 $ 434.1 $ 866.6 PSNH (Millions of Dollars) 2020 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 61.8 $ 43.5 $ 45.9 $ 46.3 $ 43.6 $ 381.9 $ 623.0 Purchased Power and Capacity 0.6 0.6 0.6 0.6 — — 2.4 Transmission Support Commitments 4.7 — — — — — 4.7 Total $ 67.1 $ 44.1 $ 46.5 $ 46.9 $ 43.6 $ 381.9 $ 630.1 The total costs incurred under these agreements were as follows: Eversource For the Years Ended December 31, (Millions of Dollars) 2019 2018 2017 Renewable Energy $ 320.8 $ 218.5 $ 235.5 Purchased Power and Capacity 62.1 72.0 103.9 Peaker CfDs 13.0 20.9 38.7 Natural Gas Procurement 448.5 432.4 377.0 Transmission Support Commitments 21.8 23.4 19.8 Coal, Wood and Other (1) — — 47.7 For the Years Ended December 31, 2019 2018 2017 (Millions of Dollars) CL&P NSTAR PSNH CL&P NSTAR PSNH CL&P NSTAR PSNH Renewable Energy $ 160.6 $ 89.9 $ 70.3 $ 63.2 $ 89.8 $ 65.5 $ 51.0 $ 123.7 $ 60.8 Purchased Power and Capacity 50.4 5.1 6.6 49.4 4.4 18.2 81.0 4.0 18.9 Peaker CfDs 13.0 — — 20.9 — — 38.7 — — Transmission Support Commitments 8.6 8.6 4.6 9.2 9.2 5.0 7.8 7.8 4.2 Coal, Wood and Other (1) — — — — — — — — 47.7 (1)
Schedule of Guarantor Obligations	The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries and affiliates to external parties as of December 31, 2019 : Company Description Maximum Exposure (in millions) Expiration Dates Various Surety Bonds (1) $ 29.2 2020 - 2021 Rocky River Realty Company and Eversource Service Lease Payments for Real Estate 6.5 2024 Bay State Wind LLC Real Estate Purchase 2.5 2020 Sunrise Wind LLC Offshore Wind (2) 2.2 — (1) Surety bond expiration dates reflect termination dates, the majority of which will be renewed or extended. Certain surety bonds contain credit ratings triggers that would require Eversource parent to post collateral in the event that the unsecured debt credit ratings of Eversource parent are downgraded. (2) On October 25, 2019, Eversource parent issued a guaranty on behalf of its 50 percent -owned affiliate, Sunrise Wind LLC, whereby Eversource parent will guaranty Sunrise Wind LLC's performance of certain obligations, in an amount not to exceed $15.4 million

LEASES (Tables)

LEASES (Tables)	12 Months Ended
LEASES (Tables)	Dec. 31, 2019
Leases [Abstract]
Components of Lease Cost	The components of lease cost, prior to amounts capitalized, are as follows: For the Year Ended December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Financing Lease Cost: Amortization of Right-of-use-Assets $ 1.7 $ 0.7 $ 0.2 $ 0.1 Interest on Lease Liabilities 1.2 0.6 0.6 — Total Finance Lease Cost 2.9 1.3 0.8 0.1 Operating Lease Cost 11.7 0.5 3.4 0.1 Variable Lease Cost 60.5 13.3 — 47.2 Total Lease Cost $ 75.1 $ 15.1 $ 4.2 $ 47.4
Schedule of Rent Expense	Operating lease rental payments charged to expense in 2018 and 2017 (which exclude CL&P's and PSNH's energy purchase contracts) were as follows: (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2018 $ 10.8 $ 10.9 $ 11.8 $ 2.5 2017 10.5 11.7 11.3 3.3
Supplemental Balance Sheet Information Related to Leases	Supplemental balance sheet information related to leases is as follows: As of December 31, 2019 (Millions of Dollars) Balance Sheet Classification Eversource CL&P NSTAR Electric PSNH Operating Leases: Operating Lease Right-of-use-Assets, Net Other Long-Term Assets $ 49.9 $ 0.7 $ 24.2 $ 0.4 Operating Lease Liabilities Operating Lease Liabilities - Current Portion Other Current Liabilities $ 8.6 $ 0.5 $ 0.7 $ 0.1 Operating Lease Liabilities - Long-Term Other Long-Term Liabilities 41.3 0.2 23.5 0.3 Total Operating Lease Liabilities $ 49.9 $ 0.7 $ 24.2 $ 0.4 Finance Leases: Finance Lease Right-of-use-Assets, Net Property, Plant and Equipment, Net $ 8.2 $ 1.9 $ 3.3 $ 0.9 Finance Lease Liabilities Finance Lease Liabilities - Current Portion Other Current Liabilities $ 2.4 $ 1.6 $ — $ 0.1 Finance Lease Liabilities - Long-Term Other Long-Term Liabilities 8.1 1.4 4.4 0.8 Total Finance Lease Liabilities $ 10.5 $ 3.0 $ 4.4 $ 0.9
Other Information Related to Leases	Other information related to leases is as follows (in millions of dollars, unless otherwise noted): Eversource CL&P NSTAR Electric PSNH As of December 31, 2019 Weighted-Average Remaining Lease Term (Years): Operating Leases 12 2 20 9 Finance Leases 12 2 22 9 Weighted-Average Discount Rate (Percentage): Operating Leases 3.9 % 2.5 % 4.1 % 3.7 % Finance Leases 4.0 % 10.5 % 2.9 % 3.5 % Eversource CL&P NSTAR Electric PSNH For the Year Ended December 31, 2019 Cash Paid for Amounts Included in the Measurement of Lease Liabilities: Operating Cash Flows from Operating Leases $ 11.4 $ 0.4 $ 1.6 $ 0.1 Operating Cash Flows from Finance Leases 1.2 0.6 0.6 — Financing Cash Flows from Finance Leases 2.6 1.4 — 0.1 Supplemental Non-Cash Information on Lease Liabilities: Right-of-use-Assets Obtained in Exchange for New Operating Lease Liabilities 2.9 1.0 0.1 0.2 Right-of-use-Assets Obtained in Exchange for New Finance Lease Liabilities 2.0 — — —
Future Minimum Lease Payments under Long-Term Leases	Future minimum lease payments, excluding variable costs, under long-term leases, as of December 31, 2019 are as follows: Operating Leases Finance Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Year Ending December 31, 2020 $ 10.2 $ 0.5 $ 1.8 $ 0.1 $ 3.4 $ 2.0 $ 0.6 $ 0.1 2021 9.0 0.2 1.6 0.1 2.9 1.5 0.6 0.1 2022 7.4 — 1.6 0.1 1.5 — 0.6 0.1 2023 4.9 — 1.6 — 0.8 — 0.6 0.1 2024 2.8 — 1.7 — 0.8 — 0.7 0.1 Thereafter 28.9 0.1 28.7 0.2 13.1 — 12.6 0.5 Future lease payments 63.2 0.8 37.0 0.5 22.5 3.5 15.7 1.0 Less amount representing interest 13.3 0.1 12.8 0.1 12.0 0.5 11.3 0.1 Present value of future minimum lease payments $ 49.9 $ 0.7 $ 24.2 $ 0.4 $ 10.5 $ 3.0 $ 4.4 $ 0.9
Future Minimum Lease Payments under Long-Term Leases	Future minimum lease payments, excluding variable costs, under long-term leases, as of December 31, 2019 are as follows: Operating Leases Finance Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Year Ending December 31, 2020 $ 10.2 $ 0.5 $ 1.8 $ 0.1 $ 3.4 $ 2.0 $ 0.6 $ 0.1 2021 9.0 0.2 1.6 0.1 2.9 1.5 0.6 0.1 2022 7.4 — 1.6 0.1 1.5 — 0.6 0.1 2023 4.9 — 1.6 — 0.8 — 0.6 0.1 2024 2.8 — 1.7 — 0.8 — 0.7 0.1 Thereafter 28.9 0.1 28.7 0.2 13.1 — 12.6 0.5 Future lease payments 63.2 0.8 37.0 0.5 22.5 3.5 15.7 1.0 Less amount representing interest 13.3 0.1 12.8 0.1 12.0 0.5 11.3 0.1 Present value of future minimum lease payments $ 49.9 $ 0.7 $ 24.2 $ 0.4 $ 10.5 $ 3.0 $ 4.4 $ 0.9
Future Minimum Rental Payments under Operating Leases	At December 31, 2018, future minimum rental payments, excluding executory costs, such as property taxes, state use taxes, insurance, and maintenance were as follows: Operating Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 11.5 $ 1.5 $ 7.2 $ 0.5 2020 9.8 1.4 6.0 0.4 2021 8.7 1.2 5.3 0.4 2022 7.2 1.1 4.4 0.4 2023 4.7 0.5 3.1 0.2 Thereafter 32.7 0.2 29.5 0.3 Future minimum lease payments $ 74.6 $ 5.9 $ 55.5 $ 2.2
Future Minimum Rental Payments under Capital Leases	Capital Leases (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH 2019 $ 3.4 $ 2.0 $ 0.5 $ 0.1 2020 3.4 2.0 0.5 0.1 2021 2.9 1.5 0.5 0.1 2022 1.5 — 0.6 0.1 2023 0.7 — 0.6 0.1 Thereafter 13.9 — 13.4 0.5 Future minimum lease payments 25.8 5.5 16.1 1.0 Less amount representing interest 13.8 1.0 12.4 0.1 Present value of future minimum lease payments $ 12.0 $ 4.5 $ 3.7 $ 0.9

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Carrying Amounts and Estimated Fair Values of Financial Instruments	The fair values provided in the table below are classified as Level 2 within the fair value hierarchy. Carrying amounts and estimated fair values are as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value As of December 31, 2019: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 162.0 $ 116.2 $ 117.8 $ 43.0 $ 44.2 $ — $ — Long-Term Debt 14,098.2 15,170.2 3,518.1 4,058.0 3,342.1 3,659.9 951.6 1,005.7 Rate Reduction Bonds 583.3 625.9 — — — — 583.3 625.9 As of December 31, 2018: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 156.8 $ 116.2 $ 113.8 $ 43.0 $ 43.0 $ — $ — Long-Term Debt 13,086.1 13,154.9 3,254.0 3,429.2 2,944.8 3,024.1 805.2 819.5 Rate Reduction Bonds 635.7 645.8 — — — — 635.7 645.8

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Tables)	12 Months Ended
ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Tables)	Dec. 31, 2019
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income/(Loss) by Component, Net of Tax	The changes in accumulated other comprehensive income/(loss) by component, net of tax, are as follows: For the Year Ended December 31, 2019 For the Year Ended December 31, 2018 Eversource (Millions of Dollars) Qualified Cash Flow Hedging Instruments Unrealized Defined Benefit Plans Total Qualified Cash Flow Hedging Instruments Unrealized Defined Benefit Plans Total Balance as of January 1st $ (4.4 ) $ (0.5 ) $ (55.1 ) $ (60.0 ) $ (6.2 ) $ — $ (60.2 ) $ (66.4 ) OCI Before Reclassifications — 1.2 (13.3 ) (12.1 ) — (0.5 ) 0.3 (0.2 ) Amounts Reclassified from AOCI 1.4 — 5.6 7.0 1.8 — 4.8 6.6 Net OCI 1.4 1.2 (7.7 ) (5.1 ) 1.8 (0.5 ) 5.1 6.4 Balance as of December 31st $ (3.0 ) $ 0.7 $ (62.8 ) $ (65.1 ) $ (4.4 ) $ (0.5 ) $ (55.1 ) $ (60.0 )
Schedule of Amounts Reclassified From AOCI By Component	The following table sets forth the amounts reclassified from AOCI by component and the impacted line item on the statements of income: Amounts Reclassified from AOCI Eversource (Millions of Dollars) For the Years Ended December 31, Statements of Income Line Item Impacted 2019 2018 2017 Qualified Cash Flow Hedging Instruments $ (2.5 ) $ (2.8 ) $ (3.3 ) Interest Expense Tax Effect 1.1 1.0 1.3 Income Tax Expense Qualified Cash Flow Hedging Instruments, Net of Tax $ (1.4 ) $ (1.8 ) $ (2.0 ) Defined Benefit Plan Costs: Amortization of Actuarial Losses $ (5.7 ) $ (6.0 ) $ (6.2 ) Other Income, Net (1) Amortization of Prior Service Cost (1.8 ) (0.4 ) (1.1 ) Other Income, Net (1) Total Defined Benefit Plan Costs (7.5 ) (6.4 ) (7.3 ) Tax Effect 1.9 1.6 2.8 Income Tax Expense Defined Benefit Plan Costs, Net of Tax $ (5.6 ) $ (4.8 ) $ (4.5 ) Total Amounts Reclassified from AOCI, Net of Tax $ (7.0 ) $ (6.6 ) $ (6.5 ) (1) These amounts are included in the computation of net periodic Pension, SERP and PBOP costs. See Note 1M, "Summary of Significant Accounting Policies – Other Income, Net" and Note 11A, "Employee Benefits – Pension Benefits and Postretirement Benefits Other Than Pension," for further information.

COMMON SHARES (Tables)

COMMON SHARES (Tables)	12 Months Ended
COMMON SHARES (Tables)	Dec. 31, 2019
Equity [Abstract]
Common Shares Authorized and Issued	The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Par Value Authorized as of December 31, 2019 and 2018 Issued as of December 31, 2019 2018 Eversource $ 5 380,000,000 345,858,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301 Details of preferred stock not subject to mandatory redemption are as follows (in millions, except in redemption price and shares): Redemption Price Per Share Shares Outstanding as of December 31, As of December 31, Series 2019 2018 2019 2018 CL&P $1.90 Series of 1947 $ 52.50 163,912 163,912 $ 8.2 $ 8.2 $2.00 Series of 1947 $ 54.00 336,088 336,088 16.8 16.8 $2.04 Series of 1949 $ 52.00 100,000 100,000 5.0 5.0 $2.20 Series of 1949 $ 52.50 200,000 200,000 10.0 10.0 3.90% Series of 1949 $ 50.50 160,000 160,000 8.0 8.0 $2.06 Series E of 1954 $ 51.00 200,000 200,000 10.0 10.0 $2.09 Series F of 1955 $ 51.00 100,000 100,000 5.0 5.0 4.50% Series of 1956 $ 50.75 104,000 104,000 5.2 5.2 4.96% Series of 1958 $ 50.50 100,000 100,000 5.0 5.0 4.50% Series of 1963 $ 50.50 160,000 160,000 8.0 8.0 5.28% Series of 1967 $ 51.43 200,000 200,000 10.0 10.0 $3.24 Series G of 1968 $ 51.84 300,000 300,000 15.0 15.0 6.56% Series of 1968 $ 51.44 200,000 200,000 10.0 10.0 Total CL&P 2,324,000 2,324,000 $ 116.2 $ 116.2 NSTAR Electric 4.25% Series of 1956 $ 103.625 180,000 180,000 $ 18.0 $ 18.0 4.78% Series of 1958 $ 102.80 250,000 250,000 25.0 25.0 Total NSTAR Electric 430,000 430,000 $ 43.0 $ 43.0 Fair Value Adjustment due to Merger with NSTAR (3.6 ) (3.6 ) Other 6.00% Series of 1958 $ 100.00 23 23 $ — $ — Total Eversource - Noncontrolling Interest - Preferred Stock of Subsidiaries $ 155.6 $ 155.6

PREFERRED STOCK NOT SUBJECT T_2

PREFERRED STOCK NOT SUBJECT TO MANDATORY REDEMPTION (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of Preferred Stock Not Subject to Mandatory Redemption	The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Par Value Authorized as of December 31, 2019 and 2018 Issued as of December 31, 2019 2018 Eversource $ 5 380,000,000 345,858,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301 Details of preferred stock not subject to mandatory redemption are as follows (in millions, except in redemption price and shares): Redemption Price Per Share Shares Outstanding as of December 31, As of December 31, Series 2019 2018 2019 2018 CL&P $1.90 Series of 1947 $ 52.50 163,912 163,912 $ 8.2 $ 8.2 $2.00 Series of 1947 $ 54.00 336,088 336,088 16.8 16.8 $2.04 Series of 1949 $ 52.00 100,000 100,000 5.0 5.0 $2.20 Series of 1949 $ 52.50 200,000 200,000 10.0 10.0 3.90% Series of 1949 $ 50.50 160,000 160,000 8.0 8.0 $2.06 Series E of 1954 $ 51.00 200,000 200,000 10.0 10.0 $2.09 Series F of 1955 $ 51.00 100,000 100,000 5.0 5.0 4.50% Series of 1956 $ 50.75 104,000 104,000 5.2 5.2 4.96% Series of 1958 $ 50.50 100,000 100,000 5.0 5.0 4.50% Series of 1963 $ 50.50 160,000 160,000 8.0 8.0 5.28% Series of 1967 $ 51.43 200,000 200,000 10.0 10.0 $3.24 Series G of 1968 $ 51.84 300,000 300,000 15.0 15.0 6.56% Series of 1968 $ 51.44 200,000 200,000 10.0 10.0 Total CL&P 2,324,000 2,324,000 $ 116.2 $ 116.2 NSTAR Electric 4.25% Series of 1956 $ 103.625 180,000 180,000 $ 18.0 $ 18.0 4.78% Series of 1958 $ 102.80 250,000 250,000 25.0 25.0 Total NSTAR Electric 430,000 430,000 $ 43.0 $ 43.0 Fair Value Adjustment due to Merger with NSTAR (3.6 ) (3.6 ) Other 6.00% Series of 1958 $ 100.00 23 23 $ — $ — Total Eversource - Noncontrolling Interest - Preferred Stock of Subsidiaries $ 155.6 $ 155.6

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
EARNINGS PER SHARE (Tables)	Dec. 31, 2019
Earnings Per Share [Abstract]
Components of Basic and Diluted EPS	The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Years Ended December 31, 2019 2018 2017 Net Income Attributable to Common Shareholders $ 909.1 $ 1,033.0 $ 988.0 Weighted Average Common Shares Outstanding: Basic 321,416,086 317,370,369 317,411,097 Dilutive Effect of: Share-Based Compensation Awards and Other 762,215 623,565 620,483 Equity Forward Sale Agreement 763,335 — — Total Dilutive Effect 1,525,550 623,565 620,483 Diluted 322,941,636 317,993,934 318,031,580 Basic EPS $ 2.83 $ 3.25 $ 3.11 Diluted EPS $ 2.81 $ 3.25 $ 3.11

REVENUES (Tables)

REVENUES (Tables)	12 Months Ended
REVENUES (Tables)	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	The following table presents operating revenues disaggregated by revenue source: For the Year Ended December 31, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 3,723.7 $ 555.1 $ — $ 132.3 $ — $ — $ 4,411.1 Commercial 2,584.8 347.6 — 63.9 — (4.3 ) 2,992.0 Industrial 331.8 96.9 — 4.5 — (11.6 ) 421.6 Total Retail Tariff Sales Revenues 6,640.3 999.6 — 200.7 — (15.9 ) 7,824.7 Wholesale Transmission Revenues — — 1,293.3 — 61.3 (1,085.2 ) 269.4 Wholesale Market Sales Revenues 215.7 55.4 — 4.1 — — 275.2 Other Revenues from Contracts with Customers 54.8 2.8 13.2 7.0 967.2 (969.0 ) 76.0 Reserve for Revenues Subject to Refund 1.3 6.2 — (2.8 ) — — 4.7 Total Revenues from Contracts with Customers 6,912.1 1,064.0 1,306.5 209.0 1,028.5 (2,070.1 ) 8,450.0 Alternative Revenue Programs 45.9 (4.9 ) 81.8 4.6 — (74.2 ) 53.2 Other Revenues 18.5 3.1 0.7 1.0 — — 23.3 Total Operating Revenues $ 6,976.5 $ 1,062.2 $ 1,389.0 $ 214.6 $ 1,028.5 $ (2,144.3 ) $ 8,526.5 For the Year Ended December 31, 2018 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 3,766.6 $ 542.5 $ — $ 130.7 $ — $ — $ 4,439.8 Commercial 2,634.7 334.8 — 63.3 — (4.5 ) 3,028.3 Industrial 351.9 96.0 — 4.4 — (10.0 ) 442.3 Total Retail Tariff Sales Revenues 6,753.2 973.3 — 198.4 — (14.5 ) 7,910.4 Wholesale Transmission Revenues — — 1,308.9 — 47.3 (1,092.2 ) 264.0 Wholesale Market Sales Revenues 179.5 57.5 — 4.1 — — 241.1 Other Revenues from Contracts with Customers 65.9 (2.2 ) 12.6 7.2 889.0 (891.0 ) 81.5 Reserve for Revenues Subject to Refund (12.3 ) (8.3 ) — (3.7 ) — — (24.3 ) Total Revenues from Contracts with Customers 6,986.3 1,020.3 1,321.5 206.0 936.3 (1,997.7 ) 8,472.7 Alternative Revenue Programs (47.0 ) (1.2 ) (35.2 ) 5.4 — 31.9 (46.1 ) Other Revenues 17.9 3.1 — 0.6 — — 21.6 Total Operating Revenues $ 6,957.2 $ 1,022.2 $ 1,286.3 $ 212.0 $ 936.3 $ (1,965.8 ) $ 8,448.2 For the Years Ended December 31, 2019 2018 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,837.1 $ 1,322.1 $ 564.5 $ 1,828.2 $ 1,380.9 $ 557.5 Commercial 922.9 1,349.4 314.6 928.1 1,391.5 316.9 Industrial 138.3 115.8 77.7 147.7 124.9 79.3 Total Retail Tariff Sales Revenues 2,898.3 2,787.3 956.8 2,904.0 2,897.3 953.7 Wholesale Transmission Revenues 587.1 517.3 188.9 620.6 488.8 199.5 Wholesale Market Sales Revenues 105.1 73.1 37.5 48.3 76.1 56.6 Other Revenues from Contracts with Customers 36.4 18.7 15.6 35.0 28.9 15.5 Reserve for Revenues Subject to Refund — — 1.3 — — (12.3 ) Total Revenues from Contracts with Customers 3,626.9 3,396.4 1,200.1 3,607.9 3,491.1 1,213.0 Alternative Revenue Programs 77.5 41.6 8.6 (65.9 ) 0.9 (17.3 ) Other Revenues 10.3 7.0 1.9 8.5 8.3 1.1 Eliminations (482.1 ) (400.4 ) (144.7 ) (454.3 ) (387.4 ) (149.2 ) Total Operating Revenues $ 3,232.6 $ 3,044.6 $ 1,065.9 $ 3,096.2 $ 3,112.9 $ 1,047.6

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
SEGMENT INFORMATION (Tables)	Dec. 31, 2019
Segment Reporting [Abstract]
Summary of Segment Information and Segmented Total Assets	Eversource's segment information is as follows: For the Year Ended December 31, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 6,976.5 $ 1,062.2 $ 1,389.0 $ 214.6 $ 1,028.5 $ (2,144.3 ) $ 8,526.5 Depreciation and Amortization (651.3 ) (68.3 ) (253.3 ) (46.9 ) (63.2 ) 2.3 (1,080.7 ) Impairment of Northern Pass Transmission — — (239.6 ) — — — (239.6 ) Other Operating Expenses (5,525.1 ) (830.8 ) (411.2 ) (101.0 ) (891.3 ) 2,143.7 (5,615.7 ) Operating Income 800.1 163.1 484.9 66.7 74.0 1.7 1,590.5 Interest Expense (206.4 ) (47.4 ) (125.7 ) (34.6 ) (170.3 ) 51.2 (533.2 ) Interest Income 13.3 0.1 1.5 — 48.7 (50.8 ) 12.8 Other Income, Net 46.8 1.6 29.2 0.4 1,041.5 (999.5 ) 120.0 Income Tax (Expense)/Benefit (135.9 ) (21.2 ) (130.5 ) 2.4 11.7 — (273.5 ) Net Income 517.9 96.2 259.4 34.9 1,005.6 (997.4 ) 916.6 Net Income Attributable to Noncontrolling Interests (4.6 ) — (2.9 ) — — — (7.5 ) Net Income Attributable to Common Shareholders $ 513.3 $ 96.2 $ 256.5 $ 34.9 $ 1,005.6 $ (997.4 ) $ 909.1 Total Assets (as of) $ 22,541.9 $ 4,345.5 $ 10,904.0 $ 2,351.7 $ 20,469.6 $ (19,488.8 ) $ 41,123.9 Cash Flows Used for Investments in Plant $ 1,104.2 $ 460.2 $ 987.0 $ 118.0 $ 242.1 $ — $ 2,911.5 For the Year Ended December 31, 2018 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues (1) $ 6,957.2 $ 1,022.2 $ 1,286.3 $ 212.0 $ 936.3 $ (1,965.8 ) $ 8,448.2 Depreciation and Amortization (671.8 ) (75.0 ) (231.8 ) (46.5 ) (49.1 ) 2.2 (1,072.0 ) Other Operating Expenses (1) (5,548.6 ) (787.6 ) (375.5 ) (99.8 ) (831.5 ) 1,966.7 (5,676.3 ) Operating Income 736.8 159.6 679.0 65.7 55.7 3.1 1,699.9 Interest Expense (202.8 ) (44.1 ) (120.6 ) (34.3 ) (129.3 ) 32.3 (498.8 ) Interest Income 18.7 — 2.4 — 30.3 (33.3 ) 18.1 Other Income/(Loss), Net 67.5 7.1 31.1 (0.4 ) 1,185.3 (1,180.3 ) 110.3 Income Tax (Expense)/Benefit (160.2 ) (29.4 ) (161.8 ) (0.1 ) 62.5 — (289.0 ) Net Income 460.0 93.2 430.1 30.9 1,204.5 (1,178.2 ) 1,040.5 Net Income Attributable to Noncontrolling Interests (4.6 ) — (2.9 ) — — — (7.5 ) Net Income Attributable to Common Shareholders $ 455.4 $ 93.2 $ 427.2 $ 30.9 $ 1,204.5 $ (1,178.2 ) $ 1,033.0 Total Assets (as of) $ 21,389.1 $ 3,904.9 $ 10,285.0 $ 2,253.0 $ 17,874.2 $ (17,464.9 ) $ 38,241.3 Cash Flows Used for Investments in Plant (2) $ 961.3 $ 351.5 $ 976.2 $ 102.3 $ 178.6 $ — $ 2,569.9 For the Year Ended December 31, 2017 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Operating Revenues (1) $ 5,542.9 $ 947.3 $ 1,301.7 $ 15.9 $ 931.0 $ (986.8 ) $ 7,752.0 Depreciation and Amortization (542.6 ) (72.9 ) (209.4 ) (3.7 ) (37.4 ) 2.2 (863.8 ) Other Operating Expenses (1) (4,072.6 ) (716.4 ) (382.8 ) (8.3 ) (806.6 ) 986.7 (5,000.0 ) Operating Income 927.7 158.0 709.5 3.9 87.0 2.1 1,888.2 Interest Expense (186.3 ) (43.1 ) (115.1 ) (3.1 ) (90.0 ) 15.8 (421.8 ) Interest Income 7.3 0.1 1.8 0.1 15.7 (16.7 ) 8.3 Other Income, Net 41.6 3.8 27.3 — 1,113.0 (1,086.0 ) 99.7 Income Tax Expense (288.3 ) (44.2 ) (228.7 ) (2.1 ) (15.5 ) (0.1 ) (578.9 ) Net Income/(Loss) 502.0 74.6 394.8 (1.2 ) 1,110.2 (1,084.9 ) 995.5 Net Income Attributable to Noncontrolling Interests (4.6 ) — (2.9 ) — — — (7.5 ) Net Income/(Loss) Attributable to Common $ 497.4 $ 74.6 $ 391.9 $ (1.2 ) $ 1,110.2 $ (1,084.9 ) $ 988.0 Cash Flows Used for Investments in Plant $ 1,020.7 $ 298.2 $ 867.6 $ 16.0 $ 145.6 $ — $ 2,348.1 (1) Effective January 1, 2018, upon implementation of the new revenue accounting guidance, the electric distribution segment is presented gross and intercompany transmission billings are presented in the eliminations column, as Eversource believes that the electric distribution segment acts as a principal, rather than an agent, in its contracts with retail customers. Retail customers contract directly with the electric distribution utility and do not differentiate between distribution and transmission services. Therefore, the electric distribution segment revenues, which are derived from retail customer billings, are presented gross of the eliminations. Prior to 2018, the electric distribution segment presented intercompany electric transmission billings net, based on indicators of net presentation prior to the new revenue guidance. See Note 23 "Revenues," to the financial statements regarding accounting for revenues. (2) See Note 1B, "Summary of Significant Accounting Policies - Basis of Presentation," for information regarding the correction of cash investments in plant reported in 2018.

ACQUISITION OF AQUARION AND G_2

ACQUISITION OF AQUARION AND GOODWILL (Tables)	12 Months Ended
ACQUISITION OF AQUARION AND GOODWILL (Tables)	Dec. 31, 2019
Business Combinations [Abstract]
Summary of Unaudited Pro Forma Financial Information	The unaudited pro forma financial information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Eversource. (Pro forma amounts in millions, except share amounts) For the Year Ended December 31, 2017 Operating Revenues $ 7,947.7 Net Income Attributable to Common Shareholders 1,019.1 Basic EPS 3.21 Diluted EPS 3.20
Summary of Goodwill by Reportable Segment	The following table presents goodwill by reportable segment as of December 31, 2019 and 2018 : (Billions of Dollars) Electric Distribution Electric Transmission Natural Gas Distribution Water Distribution Total Goodwill $ 2.5 $ 0.6 $ 0.4 $ 0.9 $ 4.4

QUARTERLY FINANCIAL DATA (UNA_2

QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	12 Months Ended
QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Schedule of Quarterly Financial Information	Quarter Ended Eversource (Millions of Dollars, except per share information) 2019 2018 March 31, June 30, (2) September 30, December 31, March 31, June 30, September 30, December 31, Operating Revenues $ 2,415.8 $ 1,884.5 $ 2,175.8 $ 2,050.4 $ 2,288.0 $ 1,853.9 $ 2,271.4 $ 2,034.9 Operating Income 494.7 151.0 509.2 435.6 442.5 391.4 466.0 400.0 Net Income 310.6 33.3 320.8 251.9 271.4 244.6 291.3 233.2 Net Income Attributable to Common Shareholders 308.7 31.5 318.9 250.0 269.5 242.8 289.4 231.3 Basic EPS (1) $ 0.97 $ 0.10 $ 0.98 $ 0.77 $ 0.85 $ 0.76 $ 0.91 $ 0.73 Diluted EPS (1) $ 0.97 $ 0.10 $ 0.98 $ 0.76 $ 0.85 $ 0.76 $ 0.91 $ 0.73 (1) The summation of quarterly EPS data may not equal annual data due to rounding. (2) In the second quarter of 2019, Eversource recorded an impairment charge related to NPT of $239.6 million within Operating Income on the statement of income. For further information, see Note 1D, "Summary of Significant Accounting Policies - Impairment of Northern Pass Transmission," to the financial statements. Quarter Ended 2019 2018 (Millions of Dollars) March 31, June 30, September 30, December 31, March 31, June 30, September 30, December 31, CL&P Operating Revenues $ 849.2 $ 740.8 $ 853.9 $ 788.7 $ 785.0 $ 694.9 $ 865.0 $ 751.3 Operating Income 171.8 166.8 190.3 152.7 157.2 163.1 172.7 142.8 Net Income 110.5 104.8 111.7 83.9 98.6 99.7 100.3 79.1 NSTAR Electric Operating Revenues $ 797.6 $ 681.9 $ 878.7 $ 686.4 $ 770.1 $ 690.7 $ 939.5 $ 712.6 Operating Income 137.8 134.2 219.4 135.5 119.0 133.6 205.5 126.0 Net Income 94.0 89.7 154.9 93.4 77.1 87.9 140.6 77.5 PSNH Operating Revenues $ 276.4 $ 240.9 $ 280.4 $ 268.2 $ 267.4 $ 235.1 $ 290.2 $ 254.9 Operating Income 49.7 46.3 64.5 56.0 55.8 46.9 56.5 37.2 Net Income 32.8 26.9 40.9 33.4 35.1 25.8 40.7 14.3

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ / shares in Units, $ in Thousands, customer in Millions	Feb. 26, 2020USD ($)	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)utilitycustomer$ / sharesMW	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Jan. 01, 2019USD ($)
Summary of Accounting Policies [Line Items]
Number of electric and natural gas customers \| customer			4,000,000
Increase to operating cash inflows in accounts payable			$ (14,866)	$ (24,481)	$ (56,067)
Increase to investing cash outflows in investments in property, plant and equipment			2,911,489	2,569,936	2,348,105
Goodwill			4,427,266	4,427,266
Operating lease liabilities			49,900
Operating lease right-of-use-assets			49,900
Pre-tax impairment charge		$ 239,600	239,644	0	0
After-tax impact of impairment charge			$ 204,400
After-tax impact of impairment charge (in dollars per share) \| $ / shares			$ 0.64
Columbia Gas of Massachusetts (CMA) \| Subsequent Event
Summary of Accounting Policies [Line Items]
Purchase price	$ 1,100,000
CL&P
Summary of Accounting Policies [Line Items]
Increase to operating cash inflows in accounts payable			$ (102,344)	76,924	(48,032)
Increase to investing cash outflows in investments in property, plant and equipment			917,532	864,136	824,383
Operating lease liabilities			700
Operating lease right-of-use-assets			$ 700
Period of accounts receivable recoverable under financial or medical duress			180 days
Transfer of loans receivable				41,300
Maximum loans receivable outstanding			$ 55,000
Loans transferred receivable current			16,500	18,500
Loans transferred receivable non-current			18,200	22,800
Long term receivable			$ 25,000	25,000
Term of energy efficiency customer loans			3 years
Yankee Gas Services Company
Summary of Accounting Policies [Line Items]
Period of accounts receivable recoverable under financial or medical duress			90 days
NSTAR Electric
Summary of Accounting Policies [Line Items]
Increase to operating cash inflows in accounts payable			$ 22,659	(37,140)	20,421
Increase to investing cash outflows in investments in property, plant and equipment			861,391	725,766	719,623
Operating lease liabilities			24,200
Operating lease right-of-use-assets			24,200
Long term receivable			5,500	5,500
PSNH
Summary of Accounting Policies [Line Items]
Increase to operating cash inflows in accounts payable			(12,281)	10,147	(29,453)
Increase to investing cash outflows in investments in property, plant and equipment			308,993	323,910	$ 312,720
Operating lease liabilities			400
Operating lease right-of-use-assets			400
Long term receivable			$ 3,800	3,800
Connecticut, Massachusetts and New Hampshire
Summary of Accounting Policies [Line Items]
Number of regulated utilities \| utility			8
Northern Pass
Summary of Accounting Policies [Line Items]
Capacity required for transmission line \| MW			1,090
Capitalized costs			$ 318,000
Accounting Standards Update 2016-02
Summary of Accounting Policies [Line Items]
Operating lease liabilities						$ 58,000
Operating lease right-of-use-assets						58,000
Accounting Standards Update 2016-02 \| CL&P
Summary of Accounting Policies [Line Items]
Operating lease liabilities						600
Operating lease right-of-use-assets						600
Accounting Standards Update 2016-02 \| NSTAR Electric
Summary of Accounting Policies [Line Items]
Operating lease liabilities						25,300
Operating lease right-of-use-assets						25,300
Accounting Standards Update 2016-02 \| PSNH
Summary of Accounting Policies [Line Items]
Operating lease liabilities						600
Operating lease right-of-use-assets						$ 600
Restatement Adjustment
Summary of Accounting Policies [Line Items]
Increase to operating cash inflows in accounts payable				(46,600)
Increase to investing cash outflows in investments in property, plant and equipment				46,600
Restatement Adjustment \| PSNH
Summary of Accounting Policies [Line Items]
Increase to operating cash inflows in accounts payable				(46,600)
Increase to investing cash outflows in investments in property, plant and equipment				$ 46,600

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Provision for Uncollectible Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	$ 224,800	$ 212,700
Provision for Uncollectible Hardship Accounts	143,300	131,500
Uncollectible Expense	63,446	61,337	$ 44,453
CL&P
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	97,300	88,000
Provision for Uncollectible Hardship Accounts	80,100	71,900
Uncollectible Expense	15,948	15,831	5,312
NSTAR Electric
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	75,400	74,500
Provision for Uncollectible Hardship Accounts	43,900	42,500
Uncollectible Expense	25,079	22,279	21,252
PSNH
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	10,500	11,100
Provision for Uncollectible Hardship Accounts	0	0
Uncollectible Expense	$ 6,726	$ 6,383	$ 6,704

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fuel, Materials, Supplies and Inventory (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Public Utilities, Inventory [Line Items]
Total	$ 235.5	$ 238
Fuel
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	26.7	33.1
Materials and Supplies
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	132.9	126.1
RECs
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	75.9	78.8
CL&P
Public Utilities, Inventory [Line Items]
Total	50.7	44.5
CL&P \| Fuel
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	0	0
CL&P \| Materials and Supplies
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	50.7	44.5
CL&P \| RECs
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	0	0
NSTAR Electric
Public Utilities, Inventory [Line Items]
Total	124.1	114.2
NSTAR Electric \| Fuel
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	0	0
NSTAR Electric \| Materials and Supplies
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	54.7	48.6
NSTAR Electric \| RECs
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	69.4	65.6
PSNH
Public Utilities, Inventory [Line Items]
Total	25	37.5
PSNH \| Fuel
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	0	0
PSNH \| Materials and Supplies
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	18.5	24.3
PSNH \| RECs
Public Utilities, Inventory [Line Items]
Other inventory, capitalized costs, gross	$ 6.5	$ 13.2

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Operating Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Accounting Policies [Line Items]
Natural gas and fuel costs	$ 462.1	$ 442.6	$ 432.5
PSNH
Summary of Accounting Policies [Line Items]
Natural gas and fuel costs	$ 0	$ 7.9	$ 43.4

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of AFUDC and Weighted Average AFUDC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of Other Operating Costs and Expense [Line Items]
Borrowed Funds	$ 25.6	$ 19.7	$ 12.5
Equity Funds	45	44	34.4
Total AFUDC	$ 70.6	$ 63.7	$ 46.9
Average AFUDC Rate	5.40%	4.90%	5.10%
CL&P
Components of Other Operating Costs and Expense [Line Items]
Borrowed Funds	$ 7.1	$ 6.3	$ 5.1
Equity Funds	13.2	12.2	12.1
Total AFUDC	$ 20.3	$ 18.5	$ 17.2
Average AFUDC Rate	6.30%	5.80%	6.20%
NSTAR Electric
Components of Other Operating Costs and Expense [Line Items]
Borrowed Funds	$ 10.4	$ 7.8	$ 4.8
Equity Funds	19.8	15.6	10.2
Total AFUDC	$ 30.2	$ 23.4	$ 15
Average AFUDC Rate	5.70%	5.00%	5.00%
PSNH
Components of Other Operating Costs and Expense [Line Items]
Borrowed Funds	$ 2.8	$ 1.3	$ 0.7
Equity Funds	3.4	0	0
Total AFUDC	$ 6.2	$ 1.3	$ 0.7
Average AFUDC Rate	4.60%	0.70%	0.70%

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Income (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Accounting Policies [Line Items]
Other Income, Net		$ 132,777	$ 128,366	$ 107,913
Other-than-temporary impairment			32,900
Unrealized gain associated with investment		42,200	3,800	27,400
Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net		31,300	60,800	29,900
AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net		45,000	44,000	34,400
Equity in Earnings of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other Income, Net		42,200	3,800	27,400
Unrealized gain associated with investment		20,400	17,600	9,700
Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other Income, Net		800	(4,000)	7,500
Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net		12,800	18,100	8,300
Gains on Sales of Property
Summary of Accounting Policies [Line Items]
Other Income, Net		300	5,100	0
Other
Summary of Accounting Policies [Line Items]
Other Income, Net		400	600	400
CL&P
Summary of Accounting Policies [Line Items]
Other Income, Net		17,531	22,663	22,991
CL&P \| Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net		500	9,500	1,800
CL&P \| AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net		13,200	12,200	12,100
CL&P \| Equity in Earnings of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other Income, Net		100	100	0
CL&P \| Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other Income, Net		2,300	(3,000)	4,500
CL&P \| Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net		1,500	3,700	4,600
CL&P \| Gains on Sales of Property
Summary of Accounting Policies [Line Items]
Other Income, Net		0	0	0
CL&P \| Other
Summary of Accounting Policies [Line Items]
Other Income, Net		(100)	200	0
NSTAR Electric
Summary of Accounting Policies [Line Items]
Other Income, Net		44,577	53,066	34,100
NSTAR Electric \| Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net		23,500	36,000	19,200
NSTAR Electric \| AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net		19,800	15,600	10,200
NSTAR Electric \| Equity in Earnings of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other Income, Net		700	700	300
NSTAR Electric \| Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other Income, Net		(400)	(500)	2,600
NSTAR Electric \| Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net		700	800	1,800
NSTAR Electric \| Gains on Sales of Property
Summary of Accounting Policies [Line Items]
Other Income, Net		100	500	0
NSTAR Electric \| Other
Summary of Accounting Policies [Line Items]
Other Income, Net		200	0	0
PSNH
Summary of Accounting Policies [Line Items]
Other Income, Net		19,222	27,672	9,805
PSNH \| Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net		4,900	9,900	5,900
PSNH \| AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net		3,400	0	0
PSNH \| Equity in Earnings of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other Income, Net		0	0	0
PSNH \| Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other Income, Net		300	(800)	1,600
PSNH \| Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net		10,500	14,100	2,200
PSNH \| Gains on Sales of Property
Summary of Accounting Policies [Line Items]
Other Income, Net		0	4,400	0
PSNH \| Other
Summary of Accounting Policies [Line Items]
Other Income, Net		100	100	$ 100
Deferred Storm Restoration Costs \| PSNH
Summary of Accounting Policies [Line Items]
Other Income, Net	$ 5,200	$ 6,300	$ 8,700

SUMMARY OF SIGNIFICANT ACCOU_10

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Other Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Accounting Policies [Line Items]
Excise and sales taxes	$ 163.1	$ 161.9	$ 157.4
Tax remittance to state for energy efficiency funds	21.4	46.8
CL&P
Summary of Accounting Policies [Line Items]
Excise and sales taxes	$ 141.1	$ 141.4	$ 137.5

SUMMARY OF SIGNIFICANT ACCOU_11

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Paid During the Year for:
Interest, Net of Amounts Capitalized	$ 532.4	$ 503.2	$ 419.1
Income Taxes	56	158.8	30.8
Non-Cash Investing Activities:
Plant Additions Included in Accounts Payable (As of)	379.4	389.3	379.5
CL&P
Cash Paid During the Year for:
Interest, Net of Amounts Capitalized	144.6	149.7	144.6
Income Taxes	80.6	66.1	68.8
Non-Cash Investing Activities:
Plant Additions Included in Accounts Payable (As of)	111.3	106.1	132.5
NSTAR Electric
Cash Paid During the Year for:
Interest, Net of Amounts Capitalized	121.9	122.1	124.6
Income Taxes	77.9	120	95.5
Non-Cash Investing Activities:
Plant Additions Included in Accounts Payable (As of)	116.4	116.5	116.5
PSNH
Cash Paid During the Year for:
Interest, Net of Amounts Capitalized	56.9	40.5	45.9
Income Taxes	3.4	27.3	26.1
Non-Cash Investing Activities:
Plant Additions Included in Accounts Payable (As of)	$ 49.9	$ 35.1	$ 44.4

SUMMARY OF SIGNIFICANT ACCOU_12

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Cash	$ 15,432	$ 108,068
Cash and Restricted Cash reported on the Statements of Cash Flows	117,063	209,324	$ 85,890	$ 106,750
CL&P
Restricted Cash and Cash Equivalents Items [Line Items]
Cash	0	87,721
Cash and Restricted Cash reported on the Statements of Cash Flows	4,971	91,613	9,619	8,403
NSTAR Electric
Restricted Cash and Cash Equivalents Items [Line Items]
Cash	52	1,606
Cash and Restricted Cash reported on the Statements of Cash Flows	6,312	14,659	14,708	15,507
PSNH
Restricted Cash and Cash Equivalents Items [Line Items]
Cash	413	1,439
Cash and Restricted Cash reported on the Statements of Cash Flows	36,688	52,723	$ 2,191	$ 5,953
Prepayments and Other Current Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	52,500	72,100
Prepayments and Other Current Assets \| CL&P
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	4,600	3,500
Prepayments and Other Current Assets \| NSTAR Electric
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	6,200	13,000
Prepayments and Other Current Assets \| PSNH
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash		47,500
Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	46,000	25,900
Marketable Securities \| CL&P
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	400	400
Marketable Securities \| NSTAR Electric
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	0	100
Marketable Securities \| PSNH
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	600	600
Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	3,200	3,200
Other Long-Term Assets \| CL&P
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	0	0
Other Long-Term Assets \| NSTAR Electric
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 0	0
Other Long-Term Assets \| PSNH
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash		$ 3,200

REGULATORY ACCOUNTING - Compone

REGULATORY ACCOUNTING - Components of Regulatory Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 5,514,700	$ 5,145,900
Less: Current Portion	651,112	514,779
Total Long-Term Regulatory Assets	4,863,639	4,631,137
Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	2,382,900	1,914,800
Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	725,800	728,600
Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	565,300	608,400
Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	540,600	576,000
Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	411,500	316,000
Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	334,500	356,500
Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	331,500	348,400
Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	97,200	89,200
Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	125,400	208,000
CL&P
Regulatory Assets [Line Items]
Total Regulatory Assets	1,735,900	1,630,700
Less: Current Portion	178,607	125,155
Total Long-Term Regulatory Assets	1,557,261	1,505,488
CL&P \| Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	539,000	424,700
CL&P \| Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	458,800	454,400
CL&P \| Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
CL&P \| Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	274,600	302,600
CL&P \| Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	78,300	33,200
CL&P \| Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	329,200	356,500
CL&P \| Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
CL&P \| Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	30,800	32,300
CL&P \| Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	25,200	27,000
NSTAR Electric
Regulatory Assets [Line Items]
Total Regulatory Assets	1,535,600	1,438,200
Less: Current Portion	285,591	241,747
Total Long-Term Regulatory Assets	1,250,029	1,196,512
NSTAR Electric \| Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	629,800	544,400
NSTAR Electric \| Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	108,000	105,900
NSTAR Electric \| Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
NSTAR Electric \| Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	200,600	212,900
NSTAR Electric \| Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	207,100	169,100
NSTAR Electric \| Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
NSTAR Electric \| Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	284,600	299,100
NSTAR Electric \| Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	50,300	42,200
NSTAR Electric \| Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	55,200	64,600
PSNH
Regulatory Assets [Line Items]
Total Regulatory Assets	945,800	929,500
Less: Current Portion	84,053	67,228
Total Long-Term Regulatory Assets	861,672	862,288
PSNH \| Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	218,200	169,600
PSNH \| Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	12,800	8,300
PSNH \| Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	565,300	608,400
PSNH \| Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	65,400	60,500
PSNH \| Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	65,800	67,300
PSNH \| Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
PSNH \| Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
PSNH \| Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	3,600	3,300
PSNH \| Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 14,700	$ 12,100

REGULATORY ACCOUNTING - Narrati

REGULATORY ACCOUNTING - Narrative (Details) - USD ($)	May 01, 2019	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 27, 2019	Apr. 17, 2019	Apr. 16, 2019	Mar. 26, 2019	Nov. 16, 2018	May 08, 2018
Regulatory Assets [Line Items]
Deferred storm restoration costs			$ 5,514,700,000	$ 5,145,900,000
Amount of regulatory costs not yet approved			146,000,000	122,900,000
Other Income, Net			132,777,000	128,366,000	$ 107,913,000
Deferred Storm Restoration Costs
Regulatory Assets [Line Items]
Deferred storm restoration costs			126,000,000
Goodwill-related
Regulatory Assets [Line Items]
Deferred storm restoration costs			$ 331,500,000	348,400,000
Recovery period			40 years
Remaining amortization			20 years
PSNH
Regulatory Assets [Line Items]
Deferred storm restoration costs			$ 945,800,000	929,500,000
Amount of regulatory costs not yet approved			18,000,000	12,200,000
Equity return not recorded on the balance sheet			6,500,000	12,000,000
Other Income, Net			19,222,000	27,672,000	9,805,000
PSNH \| Deferred Storm Restoration Costs
Regulatory Assets [Line Items]
Deferred storm restoration costs			16,000,000
Other Income, Net		$ 5,200,000	6,300,000	8,700,000
PSNH \| Storm Costs
Regulatory Assets [Line Items]
Deferred storm restoration costs						$ 68,500,000			$ 38,100,000
PSNH \| Goodwill-related
Regulatory Assets [Line Items]
Deferred storm restoration costs			0	0
CL&P
Regulatory Assets [Line Items]
Deferred storm restoration costs			1,735,900,000	1,630,700,000
Amount of regulatory costs not yet approved			51,800,000	42,100,000
Equity return not recorded on the balance sheet			500,000	700,000
Other Income, Net			17,531,000	22,663,000	22,991,000
CL&P \| Deferred Storm Restoration Costs
Regulatory Assets [Line Items]
Deferred storm restoration costs			62,000,000
CL&P \| Storm Costs
Regulatory Assets [Line Items]
Deferred storm restoration costs	$ 141,000,000						$ 141,000,000
Amount of regulatory costs not yet approved								$ 145,500,000		$ 153,000,000
Recovery period	6 years
CL&P \| Goodwill-related
Regulatory Assets [Line Items]
Deferred storm restoration costs			0	0
NSTAR Electric
Regulatory Assets [Line Items]
Deferred storm restoration costs			1,535,600,000	1,438,200,000
Amount of regulatory costs not yet approved			55,700,000	49,300,000
Other Income, Net			44,577,000	53,066,000	$ 34,100,000
NSTAR Electric \| Deferred Storm Restoration Costs
Regulatory Assets [Line Items]
Deferred storm restoration costs			48,000,000
NSTAR Electric \| Goodwill-related
Regulatory Assets [Line Items]
Deferred storm restoration costs			$ 284,600,000	$ 299,100,000
Rate Reduction Bonds \| PSNH
Regulatory Assets [Line Items]
Amount of securitized rate reduction bonds issued											$ 635,700,000

REGULATORY ACCOUNTING - Compo_2

REGULATORY ACCOUNTING - Components of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 4,019,200	$ 3,979,700
Less: Current Portion	361,152	370,230
Total Long-Term Regulatory Liabilities	3,658,042	3,609,475
EDIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	2,844,600	2,883,000
Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	559,800	521,000
Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	84,500	91,200
Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	325,100	309,000
AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	73,200	70,700
Revenue Subject to Refund due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	14,600	24,600
Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	117,400	80,200
CL&P
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,247,800	1,231,800
Less: Current Portion	82,763	109,614
Total Long-Term Regulatory Liabilities	1,164,991	1,122,157
CL&P \| EDIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,022,800	1,031,000
CL&P \| Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	64,600	39,900
CL&P \| Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
CL&P \| Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	94,800	89,500
CL&P \| AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	46,000	47,400
CL&P \| Revenue Subject to Refund due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
CL&P \| Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	19,600	24,000
NSTAR Electric
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,725,800	1,703,900
Less: Current Portion	209,180	190,620
Total Long-Term Regulatory Liabilities	1,516,585	1,513,279
NSTAR Electric \| EDIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,071,200	1,103,700
NSTAR Electric \| Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	330,600	307,100
NSTAR Electric \| Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	72,200	76,900
NSTAR Electric \| Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	165,600	163,700
NSTAR Electric \| AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	27,200	23,300
NSTAR Electric \| Revenue Subject to Refund due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
NSTAR Electric \| Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	59,000	29,200
PSNH
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	479,200	483,600
Less: Current Portion	65,766	55,526
Total Long-Term Regulatory Liabilities	413,381	428,069
PSNH \| EDIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	392,800	396,400
PSNH \| Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	16,300	22,100
PSNH \| Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
PSNH \| Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	57,000	48,300
PSNH \| AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
PSNH \| Revenue Subject to Refund due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	6,000	12,600
PSNH \| Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 7,100	$ 4,200

REGULATORY ACCOUNTING - FERC RO

REGULATORY ACCOUNTING - FERC ROE Complaints (Details) - FERC ROE First and Second Complaints $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Regulatory Assets [Line Items]
Cumulative pre-tax reserves which include impact of refunds given to customers	$ 39.1
CL&P
Regulatory Assets [Line Items]
Cumulative pre-tax reserves which include impact of refunds given to customers	21.4
NSTAR Electric
Regulatory Assets [Line Items]
Cumulative pre-tax reserves which include impact of refunds given to customers	14.6
PSNH
Regulatory Assets [Line Items]
Cumulative pre-tax reserves which include impact of refunds given to customers	$ 3.1

PROPERTY, PLANT AND EQUIPMENT_3

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Investment in Utility Property, Plant and Equipment By Asset (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Distribution - Electric	$ 15,880,000	$ 15,071,100
Distribution - Natural Gas	3,931,100	3,546,200
Transmission - Electric	10,958,400	10,153,900
Distribution - Water	1,726,500	1,639,800
Solar	200,200	164,100
Utility	32,696,200	30,575,100
Other Assets	1,025,600	778,600
Property, Plant and Equipment, Gross	33,721,800	31,353,700
Less: Accumulated Depreciation
Utility	(7,483,500)	(7,126,200)
Other	(387,400)	(336,700)
Total Accumulated Depreciation	(7,870,900)	(7,462,900)
Property, Plant and Equipment, Net	25,850,900	23,890,800
Construction Work in Progress	1,734,600	1,719,600
Total Property, Plant and Equipment, Net	27,585,470	25,610,428
CL&P
Property, Plant and Equipment [Line Items]
Distribution - Electric	6,485,500	6,176,400
Transmission - Electric	5,043,000	4,700,500
Solar	0	0
Property, Plant and Equipment, Gross	11,528,500	10,876,900
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,385,700)	(2,302,600)
Property, Plant and Equipment, Net	9,142,800	8,574,300
Construction Work in Progress	483,000	335,400
Total Property, Plant and Equipment, Net	9,625,765	8,909,701
NSTAR Electric
Property, Plant and Equipment [Line Items]
Distribution - Electric	7,163,700	6,756,400
Transmission - Electric	4,411,900	4,065,900
Solar	200,200	164,100
Property, Plant and Equipment, Gross	11,775,800	10,986,400
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,895,300)	(2,702,000)
Property, Plant and Equipment, Net	8,880,500	8,284,400
Construction Work in Progress	592,300	510,300
Total Property, Plant and Equipment, Net	9,472,770	8,794,700
PSNH
Property, Plant and Equipment [Line Items]
Distribution - Electric	2,271,100	2,178,600
Transmission - Electric	1,498,700	1,338,700
Solar	0	0
Property, Plant and Equipment, Gross	3,769,800	3,517,300
Less: Accumulated Depreciation
Total Accumulated Depreciation	(799,900)	(772,900)
Property, Plant and Equipment, Net	2,969,900	2,744,400
Construction Work in Progress	159,600	135,700
Total Property, Plant and Equipment, Net	$ 3,129,506	$ 2,880,073

PROPERTY, PLANT AND EQUIPMENT_4

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Schedule of Aggregate Composite Depreciation Rates (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Composite depreciation rate for plant in service	3.00%	2.90%	3.00%
CL&P
Property, Plant and Equipment [Line Items]
Composite depreciation rate for plant in service	2.80%	2.80%	2.80%
NSTAR Electric
Property, Plant and Equipment [Line Items]
Composite depreciation rate for plant in service	2.80%	2.80%	2.90%
PSNH
Property, Plant and Equipment [Line Items]
Composite depreciation rate for plant in service	2.80%	2.80%	3.10%

PROPERTY, PLANT AND EQUIPMENT_5

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Schedule of Average Remaining Useful Lives of Depreciable Assets (Details)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Distribution - Electric	34 years 3 months 18 days
Distribution - Natural Gas	43 years 2 months 12 days
Transmission - Electric	40 years 4 months 24 days
Distribution - Water	33 years 6 months
Solar	24 years 2 months 12 days
Other	11 years 2 months 12 days
Computer Software, Hardware and Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of property, plant and equipment	5 years
Computer Software, Hardware and Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of property, plant and equipment	15 years
Buildings
Property, Plant and Equipment [Line Items]
Estimated useful life of property, plant and equipment	40 years
CL&P
Property, Plant and Equipment [Line Items]
Distribution - Electric	35 years 3 months 18 days
Transmission - Electric	36 years 9 months 18 days
NSTAR Electric
Property, Plant and Equipment [Line Items]
Distribution - Electric	33 years 8 months 12 days
Transmission - Electric	44 years 10 months 24 days
Solar	24 years 2 months 12 days
PSNH
Property, Plant and Equipment [Line Items]
Distribution - Electric	33 years 2 months 12 days
Transmission - Electric	42 years 1 month 6 days

DERIVATIVE INSTRUMENTS - Schedu

DERIVATIVE INSTRUMENTS - Schedule of Gross Fair Value of Contracts (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Level 2 \| Current Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	$ 0	$ 1.5
Netting	0	(0.9)
Net Amount Recorded as a Derivative	0	0.6
Level 2 \| Current Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(5.2)	0
Netting	0	0
Net Amount Recorded as a Derivative	(5.2)	0
Level 2 \| Long-Term Derivative Liabilities:
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(0.1)	0
Netting	0	0
Net Amount Recorded as a Derivative	(0.1)	0
CL&P \| Level 3 \| Current Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	12.2	9.6
Netting	(0.4)	(3.4)
Net Amount Recorded as a Derivative	11.8	6.2
CL&P \| Level 3 \| Long-Term Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	67.5	74.2
Netting	(2.1)	(2.3)
Net Amount Recorded as a Derivative	65.4	71.9
CL&P \| Level 3 \| Current Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(67.8)	(55.1)
Netting	0	0
Net Amount Recorded as a Derivative	(67.8)	(55.1)
CL&P \| Level 3 \| Long-Term Derivative Liabilities:
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(338.6)	(379.5)
Netting	0	0
Net Amount Recorded as a Derivative	$ (338.6)	$ (379.5)

DERIVATIVE INSTRUMENTS - Deriva

DERIVATIVE INSTRUMENTS - Derivative Contracts at Fair Value (Details) MWh in Millions, MMBTU in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)MMBTUMWhMW	Dec. 31, 2018USD ($)MMBTUMW	Dec. 31, 2017USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of costs or benefits borne under capacity-related contracts by United Illuminated Company (as a percentage)	20.00%
Amount of power to be purchased under capacity-related contract (up to) (in MW) \| MW	676	787
Amount of natural gas to be purchased under futures contracts (in MMBtu) \| MMBTU	9.6	12.5
Loss deferred as regulatory costs \| $	$ 20.7	$ 25	$ 29
CL&P
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of costs or benefits borne under capacity-related contracts (as a percentage)	80.00%
Amount of energy to be purchased under renewable energy contract (in mwh) \| MWh	0.1
Minimum \| Level 3
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts	2.10%
Minimum \| Level 3 \| CL&P
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts	13.60%

DERIVATIVE INSTRUMENTS - Unobse

DERIVATIVE INSTRUMENTS - Unobservable Inputs Utilized (Details) - CL&P - Level 3 - $ / KWmo	Dec. 31, 2019	Dec. 31, 2018
Capacity Prices \| Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	3.01	4.30
Capacity Prices \| Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	7.34	7.44
Forward Reserve \| Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.80	0.75
Forward Reserve \| Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	1.90	1.78

DERIVATIVE INSTRUMENTS - Variat

DERIVATIVE INSTRUMENTS - Variations Using Significant unobservable Inputs (Details) - Level 3 - CL&P - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (356.5)	$ (362.3)
Net Realized/Unrealized Losses Included in Regulatory Assets	(15)	(32)
Settlements	42.3	37.8
Ending balance	$ (329.2)	$ (356.5)

MARKETABLE SECURITIES - Equity

MARKETABLE SECURITIES - Equity Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Equity securities	$ 45.7	$ 44
Amortized Cost	228.4	190
Pre-Tax Unrealized Gains	5.8	0.4
Pre-Tax Unrealized Losses	(0.1)	(4)
Fair Value	234.1	186.4
CYAPC and YAEC
Debt Securities, Available-for-sale [Line Items]
Equity securities	182.8	200
Marketable securities held in nuclear decommissioning trusts	198.1	143.9
Accounting Standards Update 2016-01
Debt Securities, Available-for-sale [Line Items]
Unrealized gains recorded in other income	$ 9.8
Unrealized losses recorded in other income		$ 4.3

MARKETABLE SECURITIES - Contrac

MARKETABLE SECURITIES - Contractual Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Less than one year	$ 59.2
One to five years	40.5
Six to ten years	33.6
Greater than ten years	95.1
Amortized Cost	228.4	$ 190
Fair Value
Less than one year	59.3
One to five years	41.4
Six to ten years	34.8
Greater than ten years	98.6
Total Debt Securities	$ 234.1	$ 186.4

MARKETABLE SECURITIES - Fair Va

MARKETABLE SECURITIES - Fair Value Measurement (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	$ 462.6	$ 430.4
Fair Value, Inputs, Level 1
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	274.5	269.9
Fair Value, Inputs, Level 1 \| Mutual Funds and Equities
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	228.5	244
Fair Value, Inputs, Level 1 \| Money Market Funds
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	46	25.9
Level 2
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	188.1	160.5
Level 2 \| U.S. Government Issued Debt Securities (Agency and Treasury)
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	96.8	79.6
Level 2 \| Corporate Debt Securities
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	44	39.5
Level 2 \| Asset-Backed Debt Securities
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	12.9	14
Level 2 \| Municipal Bonds
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	26.7	19.2
Level 2 \| Other Fixed Income Securities
Debt and Equity Securities, FV-NI [Line Items]
Total Marketable Securities	$ 7.7	$ 8.2

ASSET RETIREMENT OBLIGATIONS -

ASSET RETIREMENT OBLIGATIONS - Schedule of Reconciliation of Beginning and Ending Balance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance as of Beginning of Year	$ 466.2	$ 419.1
Liabilities Incurred During the Year	30.3	11.3
Liabilities Settled During the Year	(21.3)	(36.6)
Accretion	27.1	25.5
Revisions in Estimated Cash Flows	(12.8)	46.9
Balance as of End of Year	489.5	466.2
CL&P
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance as of Beginning of Year	33.5	31.5
Liabilities Incurred During the Year	0	0
Liabilities Settled During the Year	(3.6)	0
Accretion	2.2	2
Revisions in Estimated Cash Flows	(0.1)	0
Balance as of End of Year	32	33.5
NSTAR Electric
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance as of Beginning of Year	72.4	44.6
Liabilities Incurred During the Year	30.3	11.3
Liabilities Settled During the Year	0	0
Accretion	3.5	2.2
Revisions in Estimated Cash Flows	(8.7)	14.3
Balance as of End of Year	97.5	72.4
PSNH
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance as of Beginning of Year	4	25
Liabilities Incurred During the Year	0	0
Liabilities Settled During the Year	0	(21.5)
Accretion	0.2	0.5
Revisions in Estimated Cash Flows	0	0
Balance as of End of Year	$ 4.2	$ 4

INVESTMENTS IN UNCONSOLIDATED_3

INVESTMENTS IN UNCONSOLIDATED AFFILIATES - Summary of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affilitates	$ 871,633	$ 464,286
Offshore Wind Business - North East Offshore and Bay State Wind
Schedule of Equity Method Investments [Line Items]
Ownership interest	50.00%
Investments in unconsolidated affilitates	$ 649,300	234,300
Natural Gas Pipeline - Algonquin Gas Transmission, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest	15.00%
Investments in unconsolidated affilitates	$ 127,800	155,000
Renewable Energy Investment Fund
Schedule of Equity Method Investments [Line Items]
Ownership interest	90.00%
Investments in unconsolidated affilitates	$ 72,400	54,100
Other
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affilitates	$ 22,100	$ 20,900

ASSET RETIREMENT OBLIGATIONS _2

ASSET RETIREMENT OBLIGATIONS - Narrative (Details) $ in Millions	Jul. 15, 2016kV	Dec. 31, 2019USD ($)kV	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Asset Retirement Obligation [Line Items]
Asset retirement obligations		$ 489.5	$ 466.2	$ 419.1
Amount of capacity required for installation of distribution cable (in kV) \| kV	115	115
Eversource and NSTAR Electric \| Other Current Liabilities
Schedule of Asset Retirement Obligation [Line Items]
Asset retirement obligations		$ 1
CYAPC and YAEC
Schedule of Asset Retirement Obligation [Line Items]
Asset retirement obligations		$ 337.7	$ 339.9

INVESTMENTS IN UNCONSOLIDATED_4

INVESTMENTS IN UNCONSOLIDATED AFFILIATES - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)company	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Feb. 08, 2019mi²
Schedule of Equity Method Investments [Line Items]
Equity in earnings of unconsolidated affiliates, net of impairment	$ 42,200	$ 3,800	$ 27,400
Dividends received from equity method investees	$ 48,900	22,300	20,000
Number of companies that transmit hydro electricity imported from The Hydro-Quebec System in Canada \| company	2
Payments to acquire investments	$ 416,337	205,150	$ 32,634
Other-than-temporary impairment		32,900
Offshore Wind Business - North East Offshore and Bay State Wind
Schedule of Equity Method Investments [Line Items]
Carrying amount of equity method investments in excess of the underlying equity in net assets	240,300	7,200
Goodwill	$ 168,300
Ownership interest	50.00%
Revolution Wind And South Fork Wind
Schedule of Equity Method Investments [Line Items]
Ownership interest				50.00%
Area of land (in square miles) \| mi²				257
Bay State Wind
Schedule of Equity Method Investments [Line Items]
Ownership interest				50.00%
Area of land (in square miles) \| mi²				300
Hydro-Quebec System
Schedule of Equity Method Investments [Line Items]
Ownership interest	14.50%
Payments to acquire investments	$ 8,200	$ 7,600

SHORT-TERM DEBT - Narrative (De

SHORT-TERM DEBT - Narrative (Details) - USD ($)	12 Months Ended
SHORT-TERM DEBT - Narrative (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 18, 2019	Oct. 25, 2019	Dec. 08, 2017
Commercial Paper
Short-term Debt [Line Items]
Amount of commercial paper program	$ 346,300,000	$ 0
Line of Credit
Short-term Debt [Line Items]
Amount outstanding during period	0	0
Eversource \| Commercial Paper
Short-term Debt [Line Items]
Amount of commercial paper program	1,450,000,000				$ 1,450,000,000
Eversource \| Line of Credit
Short-term Debt [Line Items]
Amount of commercial paper program	$ 1,450,000,000
Debt instrument term	5 years
CL&P
Short-term Debt [Line Items]
Short-term borrowing limit approved by regulatory agency				$ 600,000,000
Notes payable to related parties	$ 63,800,000	0
NSTAR Electric
Short-term Debt [Line Items]
Short-term borrowing limit approved by regulatory agency			$ 655,000,000
Notes payable to related parties	30,300,000	0
NSTAR Electric \| Commercial Paper
Short-term Debt [Line Items]
Amount of commercial paper program	650,000,000
NSTAR Electric \| Line of Credit
Short-term Debt [Line Items]
Amount of commercial paper program	$ 650,000,000
Debt instrument term	5 years
PSNH
Short-term Debt [Line Items]
Short-term borrowing limit approved by regulatory agency	$ 354,000,000
Notes payable to related parties	$ 27,000,000	$ 57,000,000
PSNH \| Short Term Debt Authorization Calculation
Short-term Debt [Line Items]
Interest rate stated percentage (up to) (as a percentage)	10.00%
Short-term debt borrowing calculation approved by regulatory agency	$ 60,000,000
Unsecured Debt \| CL&P
Short-term Debt [Line Items]
Period of maturity restricting provisions of debt	10 years
Total capitalization (as a percentage)	10.00%
Capacity available under preferred stock provisions	$ 738,100,000

SHORT-TERM DEBT - Schedule of D

SHORT-TERM DEBT - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Borrowings Outstanding	$ 889,084	$ 910,000
Eversource Parent Commercial Paper Program
Line of Credit Facility [Line Items]
Borrowings Outstanding	878,584	631,500
Commercial Paper \| Eversource Parent Commercial Paper Program
Line of Credit Facility [Line Items]
Borrowings Outstanding	1,224,900	631,500
Available Borrowing Capacity	$ 225,100	$ 818,500
Weighted-Average Interest Rate (as a percentage)	1.98%	2.77%
Commercial Paper \| NSTAR Electric
Line of Credit Facility [Line Items]
Borrowings Outstanding	$ 10,500	$ 278,500
Available Borrowing Capacity	$ 639,500	$ 371,500
Weighted-Average Interest Rate (as a percentage)	1.63%	2.50%

LONG-TERM DEBT - Narrative (Det

LONG-TERM DEBT - Narrative (Details) - USD ($)	1 Months Ended
LONG-TERM DEBT - Narrative (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Jan. 27, 2020	Dec. 11, 2019	Aug. 14, 2019	Apr. 26, 2019	Feb. 27, 2019
Debt Instrument [Line Items]
Long-Term Debt	$ 13,770,828,000	$ 12,248,743,000
Payment to DOE	29,000,000	145,000,000
Interest included in payment to settle spent nuclear fuel obligation	8,600,000	29,000,000
NSTAR Electric
Debt Instrument [Line Items]
Amount of long-term debt approved for issuance							$ 800,000,000
Long-Term Debt	3,247,086,000	2,944,846,000
PSNH
Debt Instrument [Line Items]
Amount of long-term debt approved for issuance						$ 300,000,000
Long-Term Debt	951,620,000	655,173,000
CL&P
Debt Instrument [Line Items]
Amount of long-term debt approved for issuance					$ 675,000,000
Long-Term Debt	3,518,136,000	3,004,016,000
Aquarion
Debt Instrument [Line Items]
Amount of long-term debt approved for issuance				$ 45,000,000
Pre-1983 Spent Nuclear Fuel Obligation (CYAPC)
Debt Instrument [Line Items]
Long-Term Debt	$ 11,600,000	$ 39,500,000
Subsequent Event \| NSTAR Gas
Debt Instrument [Line Items]
Amount of long-term debt approved for issuance			$ 270,000,000

LONG-TERM DEBT - Schedule of Lo

LONG-TERM DEBT - Schedule of Long-Term Debt Outstanding (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 08, 2017
Debt Instrument [Line Items]
Long-Term Debt	$ 13,770,828,000	$ 12,248,743,000
Less Amounts due in One Year	(327,411,000)	(837,319,000)
Senior Notes
Debt Instrument [Line Items]
Unamortized Premiums and Discounts, Net	(4,100,000)	(4,200,000)
Unamortized Debt Issuance Costs	(20,600,000)	(23,200,000)
Long-term debt	13,770,800,000	12,248,700,000
Pre-1983 Spent Nuclear Fuel Obligation (CYAPC)
Debt Instrument [Line Items]
Long-Term Debt	11,600,000	39,500,000
Fair Value Adjustment
Debt Instrument [Line Items]
Long-Term Debt	109,100,000	144,700,000
Fair Value Adjustment - Current Portion
Debt Instrument [Line Items]
Long-Term Debt	(31,300,000)	(36,200,000)
Loans Payable
Debt Instrument [Line Items]
Less Amounts due in One Year	(201,100,000)	(401,100,000)
Total Other Long-Term Debt
Debt Instrument [Line Items]
Long-Term Debt	6,054,000,000	5,644,700,000
CL&P
Debt Instrument [Line Items]
Long-Term Debt	3,518,136,000	3,004,016,000
Less Amounts due in One Year	0	(250,000,000)
CL&P \| 4.375% Fixed Rate Tax Exempt due 2028
Debt Instrument [Line Items]
Long-Term Debt	120,500,000	120,500,000
CL&P \| First Mortgage Bonds:
Debt Instrument [Line Items]
Long-Term Debt	3,394,800,000	3,144,800,000
Unamortized Premiums and Discounts, Net	27,800,000	10,200,000
Unamortized Debt Issuance Costs	(25,000,000)	(21,500,000)
Long-term debt	$ 3,518,100,000	3,004,000,000
CL&P \| First Mortgage Bonds: \| 7.875% 1994 Series D due 2024
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	7.875%
Long-Term Debt	$ 139,800,000	139,800,000
CL&P \| First Mortgage Bonds: \| 5.750% 2004 Series B due 2034
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.75%
Long-Term Debt	$ 130,000,000	130,000,000
CL&P \| First Mortgage Bonds: \| 5.625% 2005 Series B due 2035
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.625%
Long-Term Debt	$ 100,000,000	100,000,000
CL&P \| First Mortgage Bonds: \| 6.350% 2006 Series A due 2036
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	6.35%
Long-Term Debt	$ 250,000,000	250,000,000
CL&P \| First Mortgage Bonds: \| 5.750% 2007 Series B due 2037
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.75%
Long-Term Debt	$ 150,000,000	150,000,000
CL&P \| First Mortgage Bonds: \| 6.375% 2007 Series D due 2037
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	6.375%
Long-Term Debt	$ 100,000,000	100,000,000
CL&P \| First Mortgage Bonds: \| 5.500% 2009 Series A due 2019
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.50%
Long-Term Debt	$ 0	250,000,000
CL&P \| First Mortgage Bonds: \| 2.500% 2013 Series A due 2023
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	2.50%
Long-Term Debt	$ 400,000,000	400,000,000
CL&P \| First Mortgage Bonds: \| 4.300% 2014 Series A due 2044
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.30%
Long-Term Debt	$ 475,000,000	475,000,000
CL&P \| First Mortgage Bonds: \| 4.150% 2015 Series A due 2045
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.15%
Long-Term Debt	$ 350,000,000	350,000,000
CL&P \| First Mortgage Bonds: \| 3.200% 2017 Series A due 2027
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.20%
Long-Term Debt	$ 500,000,000	300,000,000
CL&P \| First Mortgage Bonds: \| 4.000% 2018 Series A due 2048
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.00%
Long-Term Debt	$ 800,000,000	500,000,000
NSTAR Electric
Debt Instrument [Line Items]
Long-Term Debt	3,247,086,000	2,944,846,000
Less Amounts due in One Year	(95,000,000)	0
NSTAR Electric \| Unsecured Debt
Debt Instrument [Line Items]
Long-Term Debt	2,800,000,000	2,400,000,000
Less Amounts due in One Year	(95,000,000)	0
Unamortized Premiums and Discounts, Net	(4,100,000)	(2,500,000)
Unamortized Debt Issuance Costs	(18,800,000)	(17,700,000)
Long-term debt	$ 3,247,100,000	2,944,800,000
NSTAR Electric \| Unsecured Debt \| 5.750% due 2036
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.75%
Long-Term Debt	$ 200,000,000	200,000,000
NSTAR Electric \| Unsecured Debt \| 5.500% due 2040
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.50%
Long-Term Debt	$ 300,000,000	300,000,000
NSTAR Electric \| Unsecured Debt \| 2.375% due 2022
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	2.375%
Long-Term Debt	$ 400,000,000	400,000,000
NSTAR Electric \| Unsecured Debt \| 4.400% due 2044
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.40%
Long-Term Debt	$ 300,000,000	300,000,000
NSTAR Electric \| Unsecured Debt \| 3.250% due 2025
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.25%
Long-Term Debt	$ 250,000,000	250,000,000
NSTAR Electric \| Unsecured Debt \| 2.700% due 2026
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	2.70%
Long-Term Debt	$ 250,000,000	250,000,000
NSTAR Electric \| Unsecured Debt \| 3.200% due 2027
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.20%
Long-Term Debt	$ 700,000,000	700,000,000
NSTAR Electric \| Unsecured Debt \| 3.250% due 2029
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.25%
Long-Term Debt	$ 400,000,000	0
NSTAR Electric \| Senior Notes
Debt Instrument [Line Items]
Long-Term Debt	$ 565,000,000	565,000,000
NSTAR Electric \| Senior Notes \| 5.900% Senior Notes Series B due 2034
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.90%
Long-Term Debt	$ 50,000,000	50,000,000
NSTAR Electric \| Senior Notes \| 6.700% Senior Notes Series D due 2037
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	6.70%
Long-Term Debt	$ 40,000,000	40,000,000
NSTAR Electric \| Senior Notes \| 5.100% Senior Notes Series E due 2020
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.10%
Long-Term Debt	$ 95,000,000	95,000,000
NSTAR Electric \| Senior Notes \| 3.500% Senior Notes Series F due 2021
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.50%
Long-Term Debt	$ 250,000,000	250,000,000
NSTAR Electric \| Senior Notes \| 3.880% Senior Notes Series G due 2023
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.88%
Long-Term Debt	$ 80,000,000	80,000,000
NSTAR Electric \| Senior Notes \| 2.750% Senior Notes Series H due 2026
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	2.75%
Long-Term Debt	$ 50,000,000	50,000,000
PSNH
Debt Instrument [Line Items]
Long-Term Debt	951,620,000	655,173,000
Less Amounts due in One Year	0	(150,000,000)
PSNH \| First Mortgage Bonds:
Debt Instrument [Line Items]
Long-Term Debt	957,000,000	807,000,000
Less Amounts due in One Year	0	(150,000,000)
Unamortized Premiums and Discounts, Net	(700,000)	0
Unamortized Debt Issuance Costs	(4,700,000)	(1,800,000)
Long-term debt	$ 951,600,000	655,200,000
PSNH \| First Mortgage Bonds: \| 5.600% Series M due 2035
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	5.60%
Long-Term Debt	$ 50,000,000	50,000,000
PSNH \| First Mortgage Bonds: \| 4.500% Series P due 2019
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.50%
Long-Term Debt	$ 0	150,000,000
PSNH \| First Mortgage Bonds: \| 4.050% Series Q due 2021
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.05%
Long-Term Debt	$ 122,000,000	122,000,000
PSNH \| First Mortgage Bonds: \| 3.200% Series R due 2021
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.20%
Long-Term Debt	$ 160,000,000	160,000,000
PSNH \| First Mortgage Bonds: \| 3.500% Series S due 2023
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.50%
Long-Term Debt	$ 325,000,000	325,000,000
PSNH \| First Mortgage Bonds: \| 3.600% Series T due 2049
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.60%
Long-Term Debt	$ 300,000,000	0
Yankee Gas \| First Mortgage Bonds: \| Yankee Gas - First Mortgage Bonds: 2.230% - 8.480% due 2020 - 2049
Debt Instrument [Line Items]
Long-Term Debt	620,000,000	470,000,000
NSTAR Gas \| First Mortgage Bonds: \| NSTAR Gas - First Mortgage Bonds: 3.740% - 9.950% due 2020 - 2049
Debt Instrument [Line Items]
Long-Term Debt	$ 460,000,000	385,000,000
Aquarion \| Unsecured Debt \| Aquarion - Senior Note 4.000% due 2024
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.00%
Long-Term Debt	$ 360,000,000	360,000,000
Aquarion \| Unsecured Debt \| Aquarion - Unsecured Notes 0% - 6.430% due 2021 - 2049
Debt Instrument [Line Items]
Long-Term Debt	335,300,000	289,500,000
Aquarion \| Unsecured Debt \| Aquarion - Secured Debt 4.100% - 9.640% due 2021 - 2035
Debt Instrument [Line Items]
Long-Term Debt	68,800,000	70,700,000
Commercial Paper
Debt Instrument [Line Items]
Commercial Paper Classified as Long-Term Debt (See Note 8, Short-Term Debt)	346,300,000	0
Commercial Paper \| NSTAR Electric
Debt Instrument [Line Items]
Commercial Paper Classified as Long-Term Debt (See Note 8, Short-Term Debt)	$ 650,000,000
Minimum \| Yankee Gas \| First Mortgage Bonds: \| Yankee Gas - First Mortgage Bonds: 2.230% - 8.480% due 2020 - 2049
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	2.23%
Minimum \| NSTAR Gas \| First Mortgage Bonds: \| NSTAR Gas - First Mortgage Bonds: 3.740% - 9.950% due 2020 - 2049
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	3.74%
Minimum \| Aquarion \| Unsecured Debt \| Aquarion - Unsecured Notes 0% - 6.430% due 2021 - 2049
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	0.00%
Minimum \| Aquarion \| Unsecured Debt \| Aquarion - Secured Debt 4.100% - 9.640% due 2021 - 2035
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.10%
Maximum \| Yankee Gas \| First Mortgage Bonds: \| Yankee Gas - First Mortgage Bonds: 2.230% - 8.480% due 2020 - 2049
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	8.48%
Maximum \| NSTAR Gas \| First Mortgage Bonds: \| NSTAR Gas - First Mortgage Bonds: 3.740% - 9.950% due 2020 - 2049
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	9.95%
Maximum \| Aquarion \| Unsecured Debt \| Aquarion - Unsecured Notes 0% - 6.430% due 2021 - 2049
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	6.43%
Maximum \| Aquarion \| Unsecured Debt \| Aquarion - Secured Debt 4.100% - 9.640% due 2021 - 2035
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	9.64%
Eversource
Debt Instrument [Line Items]
Long-Term Debt	$ 4,358,339,000	4,031,997,000
Less Amounts due in One Year	$ (23,933,000)	(378,883,000)
Eversource \| Unsecured Debt \| Eversource Parent - Debentures 4.500% due 2019
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.50%
Long-Term Debt	$ 0	350,000,000
Eversource \| Unsecured Debt \| Eversource Parent - Senior Notes 2.500% - 4.250% due 2021 - 2029
Debt Instrument [Line Items]
Long-Term Debt	4,000,000,000	$ 4,000,000,000
Eversource \| Commercial Paper
Debt Instrument [Line Items]
Commercial Paper Classified as Long-Term Debt (See Note 8, Short-Term Debt)	$ 1,450,000,000		$ 1,450,000,000
Eversource \| Minimum \| Unsecured Debt \| Eversource Parent - Senior Notes 2.500% - 4.250% due 2021 - 2029
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	2.50%
Eversource \| Maximum \| Unsecured Debt \| Eversource Parent - Senior Notes 2.500% - 4.250% due 2021 - 2029
Debt Instrument [Line Items]
Interest rate stated percentage (up to) (as a percentage)	4.25%

LONG-TERM DEBT - Schedule of Is

LONG-TERM DEBT - Schedule of Issuances and Repayments (Details) - USD ($) $ in Thousands

Nov. 15, 2019

Nov. 01, 2019

Feb. 01, 2019

Jan. 31, 2020

Dec. 31, 2019

Sep. 30, 2019

Jul. 31, 2019

Jun. 30, 2019

May 31, 2019

Apr. 30, 2019

Dec. 31, 2019

Dec. 31, 2018

Dec. 31, 2017

Debt Instrument [Line Items]

Repayments of debt

$ (801,078)

$ (1,050,330)

$ (745,000)

Senior Notes

Debt Instrument [Line Items]

Long-term debt

$ 13,770,800

13,770,800

12,248,700

CL&P

Debt Instrument [Line Items]

Repayments of debt

(250,000)

(300,000)

(250,000)

CL&P | Senior Notes | 4.00% 2018 Series A First Mortgage Bonds

Debt Instrument [Line Items]

Issuance

$ 300,000

CL&P | Senior Notes | 3.20% 2017 Series A First Mortgage Bonds

Debt Instrument [Line Items]

Issuance

$ 200,000

CL&P | Senior Notes | 5.50% 2009 Series A First Mortgage Bonds

Debt Instrument [Line Items]

Repayments of debt

$ (250,000)

NSTAR Electric

Debt Instrument [Line Items]

Repayments of debt

(400,000)

NSTAR Electric | Senior Notes | 3.25% 2019 Debentures

Debt Instrument [Line Items]

Issuance

$ 400,000

PSNH

Debt Instrument [Line Items]

Repayments of debt

(150,000)

(199,250)

(70,000)

PSNH | Senior Notes | 3.60% 2019 Series T First Mortgage Bonds

Debt Instrument [Line Items]

Issuance

$ 300,000

PSNH | Senior Notes | 4.50% 2009 Series P First Mortgage Bonds

Debt Instrument [Line Items]

Repayments of debt

(150,000)

NSTAR Gas | Senior Notes | NSTAR Gas 3.74% Series Q First Mortgage Bonds

Debt Instrument [Line Items]

Issuance

$ 75,000

Yankee Gas | Senior Notes | Yankee Gas 2.23% Series P First Mortgage Bonds

Debt Instrument [Line Items]

Issuance

100,000

Yankee Gas | Senior Notes | Yankee Gas 3.30% Series Q First Mortgage Bonds

Debt Instrument [Line Items]

Issuance

$ 100,000

Yankee Gas | Senior Notes | Yankee Gas 5.26% Series H First Mortgage Bonds

Debt Instrument [Line Items]

Repayments of debt

$ (50,000)

Aquarion | Senior Notes | Aquarion 3.54% Senior Notes

Debt Instrument [Line Items]

Issuance

45,000

Eversource

Debt Instrument [Line Items]

Repayments of debt

(350,000)

$ (450,000)

$ 0

Eversource | Senior Notes | Eversource Parent 4.50% Debentures

Debt Instrument [Line Items]

Repayments of debt

$ (350,000)

Eversource | Senior Notes | Eversource Parent 3.45% Series P Senior Notes | Subsequent Event

Debt Instrument [Line Items]

Issuance

$ 350,000

Eversource | CL&P | Senior Notes | 4.00% 2018 Series A First Mortgage Bonds

Debt Instrument [Line Items]

Long-term debt

800,000

Eversource | CL&P | Senior Notes | 3.20% 2017 Series A First Mortgage Bonds

Debt Instrument [Line Items]

Long-term debt

$ 500,000

LONG-TERM DEBT - Schedule of _2

LONG-TERM DEBT - Schedule of Long-term Debt Maturities (Details) $ in Millions	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
2020	$ 296.1
2021	1,033.6
2022	1,188.9
2023	1,665.2
2024	1,049.8
Thereafter	8,447.8
Total	13,681.4
CL&P
Debt Instrument [Line Items]
2020	0
2021	0
2022	0
2023	400
2024	139.8
Thereafter	2,975.5
Total	3,515.3
NSTAR Electric
Debt Instrument [Line Items]
2020	95
2021	250
2022	400
2023	80
2024	0
Thereafter	2,540
Total	3,365
PSNH
Debt Instrument [Line Items]
2020	0
2021	282
2022	0
2023	325
2024	0
Thereafter	350
Total	$ 957

RATE REDUCTION BONDS AND VARI_3

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Narrative (Details)	May 08, 2018USD ($)
Debt Instrument [Line Items]
Weighted average interest rate	3.66%
PSNH \| Rate Reduction Bonds
Debt Instrument [Line Items]
Amount of securitized rate reduction bonds issued	$ 635,700,000

RATE REDUCTION BONDS AND VARI_4

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	$ 5,514,700	$ 5,145,900
Regulatory Liabilities	3,658,042	3,609,475
Accrued Interest (included in Other Current Liabilities)	836,834	823,006
Rate Reduction Bonds - Current Portion	43,210	52,332
Rate Reduction Bonds - Long-Term Portion	540,122	583,331
Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	565,300	608,400
Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	125,400	208,000
PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	945,800	929,500
Regulatory Liabilities	413,381	428,069
Accrued Interest (included in Other Current Liabilities)	32,736	44,093
Rate Reduction Bonds - Current Portion	43,210	52,332
Rate Reduction Bonds - Long-Term Portion	540,122	583,331
PSNH \| Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	565,300	608,400
PSNH \| Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	14,700	12,100
Variable Interest Entity, Primary Beneficiary \| PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Rate Reduction Bonds - Current Portion	43,200	52,300
Rate Reduction Bonds - Long-Term Portion	540,100	583,300
Variable Interest Entity, Primary Beneficiary \| PSNH \| Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	565,300	608,400
Variable Interest Entity, Primary Beneficiary \| PSNH \| Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory Liabilities	5,600	5,800
Accrued Interest (included in Other Current Liabilities)	8,600	14,400
Prepayments and Other Current Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	52,500	72,100
Prepayments and Other Current Assets \| PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash		47,500
Prepayments and Other Current Assets \| Variable Interest Entity, Primary Beneficiary \| PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	32,500	47,500
Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	3,200	3,200
Other Long-Term Assets \| PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash		3,200
Other Long-Term Assets \| Variable Interest Entity, Primary Beneficiary \| PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	$ 3,200	$ 3,200

RATE REDUCTION BONDS AND VARI_5

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Income Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	$ 533,197	$ 498,805	$ 421,755
PSNH
Condensed Income Statements, Captions [Line Items]
Amortization of Regulatory Assets, Net	57,732	80,978	(16,577)
Interest Expense on RRB Principal (included in Interest Expense)	60,666	60,634	$ 51,007
Variable Interest Entity, Primary Beneficiary \| Rate Reduction Bonds \| PSNH
Condensed Income Statements, Captions [Line Items]
Amortization of Regulatory Assets, Net	43,000	27,300
Interest Expense on RRB Principal (included in Interest Expense)	$ 21,100	$ 14,400

EMPLOYEE BENEFITS - Schedule of

EMPLOYEE BENEFITS - Schedule of Pension Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation as of Beginning of Year	$ (5,520)	$ (5,936.5)
Service Cost	(67.7)	(84.8)	$ (71.3)
Interest Cost	(219)	(196.4)	(188)
Actuarial Gain/(Loss)	(815.3)	414.9
Benefits Paid	273	261.8
Benefits Paid - Lump Sum	20	14.2
Benefits Paid - SERP	7.3	6.8
Employee Transfers	0	0
Benefit Obligation as of End of Year	(6,321.7)	(5,520)	(5,936.5)
Change in Pension Plan Assets:
Fair Value of Pension Plan Assets as of Beginning of Year	4,573.9	4,739.5
Employer Contributions	112.5	185.6
Actual Return on Pension Plan Assets	575.2	(75.2)
Benefits Paid - Pension	(273)	(261.8)
Benefits Paid - Lump Sum	(20)	(14.2)
Employee Transfers	0	0
Fair Value of Pension Plan Assets as of End of Year	4,968.6	4,573.9	4,739.5
Funded Status as of December 31st	(1,353.1)	(946.1)
Other Postretirement Benefits Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation as of Beginning of Year	(841.5)	(948.6)
Service Cost	(7.8)	(10)	(9.5)
Interest Cost	(32.7)	(30.7)	(27.1)
Actuarial Gain/(Loss)	(67)	102.5
Benefits Paid	50	45.3
Employee Transfers	0	0
Benefit Obligation as of End of Year	(899)	(841.5)	(948.6)
Change in Pension Plan Assets:
Fair Value of Pension Plan Assets as of Beginning of Year	849.6	922.2
Employer Contributions	9.3	9.3
Actual Return on Pension Plan Assets	127	(36.6)
Benefits Paid - Pension	(50)	(45.3)
Employee Transfers	0	0
Fair Value of Pension Plan Assets as of End of Year	935.9	849.6	922.2
Funded Status as of December 31st	36.9	8.1
CL&P \| Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation as of Beginning of Year	(1,160.4)	(1,275.2)
Service Cost	(18)	(21.4)	(18.5)
Interest Cost	(45.7)	(41.8)	(41.6)
Actuarial Gain/(Loss)	(176.6)	106.1
Benefits Paid	60.2	59.6
Benefits Paid - Lump Sum	0	0
Benefits Paid - SERP	0.3	0.3
Employee Transfers	8.9	12
Benefit Obligation as of End of Year	(1,331.3)	(1,160.4)	(1,275.2)
Change in Pension Plan Assets:
Fair Value of Pension Plan Assets as of Beginning of Year	918.4	963
Employer Contributions	24	41.2
Actual Return on Pension Plan Assets	112.9	(14.2)
Benefits Paid - Pension	(60.2)	(59.6)
Benefits Paid - Lump Sum	0	0
Employee Transfers	(8.9)	(12)
Fair Value of Pension Plan Assets as of End of Year	986.2	918.4	963
Funded Status as of December 31st	(345.1)	(242)
CL&P \| Other Postretirement Benefits Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation as of Beginning of Year	(161.7)	(178.4)
Service Cost	(1.4)	(1.9)	(1.9)
Interest Cost	(6.3)	(5.8)	(5.3)
Actuarial Gain/(Loss)	(13.4)	14.4
Benefits Paid	10.8	10.1
Employee Transfers	(0.7)	(0.1)
Benefit Obligation as of End of Year	(172.7)	(161.7)	(178.4)
Change in Pension Plan Assets:
Fair Value of Pension Plan Assets as of Beginning of Year	120.6	135.9
Employer Contributions	0	0
Actual Return on Pension Plan Assets	17.1	(5.2)
Benefits Paid - Pension	(10.8)	(10.1)
Employee Transfers	(0.6)	0
Fair Value of Pension Plan Assets as of End of Year	126.3	120.6	135.9
Funded Status as of December 31st	(46.4)	(41.1)
NSTAR Electric \| Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation as of Beginning of Year	(1,236.5)	(1,351)
Service Cost	(14.6)	(17.4)	(15.5)
Interest Cost	(49)	(43.5)	(42.7)
Actuarial Gain/(Loss)	(181)	98.6
Benefits Paid	67.1	66.9
Benefits Paid - Lump Sum	12.9	7.1
Benefits Paid - SERP	0.1	0.3
Employee Transfers	3.7	2.5
Benefit Obligation as of End of Year	(1,397.3)	(1,236.5)	(1,351)
Change in Pension Plan Assets:
Fair Value of Pension Plan Assets as of Beginning of Year	1,222.1	1,260.8
Employer Contributions	0.4	56.5
Actual Return on Pension Plan Assets	150	(18.7)
Benefits Paid - Pension	(67.1)	(66.9)
Benefits Paid - Lump Sum	(12.9)	(7.1)
Employee Transfers	(3.7)	(2.5)
Fair Value of Pension Plan Assets as of End of Year	1,288.8	1,222.1	1,260.8
Funded Status as of December 31st	(108.5)	(14.4)
NSTAR Electric \| Other Postretirement Benefits Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation as of Beginning of Year	(246.3)	(278.6)
Service Cost	(1.7)	(2)	(1.7)
Interest Cost	(9.5)	(8.7)	(8.7)
Actuarial Gain/(Loss)	(15.2)	28.4
Benefits Paid	15.4	14.5
Employee Transfers	(1)	0.1
Benefit Obligation as of End of Year	(258.3)	(246.3)	(278.6)
Change in Pension Plan Assets:
Fair Value of Pension Plan Assets as of Beginning of Year	379.1	405.5
Employer Contributions	6	5.2
Actual Return on Pension Plan Assets	57	(17.4)
Benefits Paid - Pension	(15.4)	(14.5)
Employee Transfers	(2.3)	0.3
Fair Value of Pension Plan Assets as of End of Year	424.4	379.1	405.5
Funded Status as of December 31st	166.1	132.8
PSNH \| Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation as of Beginning of Year	(610.7)	(642.2)
Service Cost	(7.1)	(11.2)	(9.7)
Interest Cost	(24)	(22)	(21.2)
Actuarial Gain/(Loss)	(84.5)	39.2
Benefits Paid	30.3	26.2
Benefits Paid - Lump Sum	0	0
Benefits Paid - SERP	0.4	0.2
Employee Transfers	3	(0.9)
Benefit Obligation as of End of Year	(692.6)	(610.7)	(642.2)
Change in Pension Plan Assets:
Fair Value of Pension Plan Assets as of Beginning of Year	506.6	539.5
Employer Contributions	15.4	0
Actual Return on Pension Plan Assets	62.9	(7.6)
Benefits Paid - Pension	(30.3)	(26.2)
Benefits Paid - Lump Sum	0	0
Employee Transfers	(3)	0.9
Fair Value of Pension Plan Assets as of End of Year	551.6	506.6	539.5
Funded Status as of December 31st	(141)	(104.1)
PSNH \| Other Postretirement Benefits Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation as of Beginning of Year	(91.9)	(101.1)
Service Cost	(0.7)	(1.1)	(1.3)
Interest Cost	(3.4)	(3.4)	(3)
Actuarial Gain/(Loss)	(3.1)	8.6
Benefits Paid	5.6	4.9
Employee Transfers	0.5	0.2
Benefit Obligation as of End of Year	(93)	(91.9)	(101.1)
Change in Pension Plan Assets:
Fair Value of Pension Plan Assets as of Beginning of Year	71.2	79
Employer Contributions	0	0
Actual Return on Pension Plan Assets	10	(2.9)
Benefits Paid - Pension	(5.6)	(4.9)
Employee Transfers	0.4	0
Fair Value of Pension Plan Assets as of End of Year	76	71.2	$ 79
Funded Status as of December 31st	$ (17)	$ (20.7)

EMPLOYEE BENEFITS - Pension Pla

EMPLOYEE BENEFITS - Pension Plan Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Liability	$ 962,510	$ 1,370,245	$ 962,510
Expected long-term rate of return		7.00%	7.00%
Compensation rate	4.00%		4.00%
CL&P
Defined Contribution Plan Disclosure [Line Items]
Liability	$ 282,771	$ 391,159	$ 282,771
PSNH
Defined Contribution Plan Disclosure [Line Items]
Liability	124,457	157,638	124,457
Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Increase in liability due to amendment in pension plan	465,000	813,100
Funded status of plan	(946,100)	(1,353,100)	$ (946,100)
Expected long-term rate of return			8.25%	8.25%
Estimated future employer contributions in next fiscal year		105,000
Estimated future contributions in the next twelve months by other subsidiaries		57,300
Pension Plan \| CL&P
Defined Contribution Plan Disclosure [Line Items]
Funded status of plan	(242,000)	(345,100)	$ (242,000)
Estimated future employer contributions in next fiscal year		23,200
Pension Plan \| PSNH
Defined Contribution Plan Disclosure [Line Items]
Funded status of plan	(104,100)	(141,000)	(104,100)
Estimated future employer contributions in next fiscal year		19,500
Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Increase in liability due to amendment in pension plan		88,600	88,000
Funded status of plan	8,100	36,900	$ 8,100
Expected long-term rate of return			8.25%	8.25%
Estimated future employer contributions in next fiscal year		2,900
Other Postretirement Benefits Plan \| CL&P
Defined Contribution Plan Disclosure [Line Items]
Funded status of plan	(41,100)	(46,400)	$ (41,100)
Other Postretirement Benefits Plan \| PSNH
Defined Contribution Plan Disclosure [Line Items]
Funded status of plan	(20,700)	(17,000)	(20,700)
Other Current Liabilities
Defined Contribution Plan Disclosure [Line Items]
Funded status of plan	8,900	8,700	8,900
Other Long-Term Assets \| Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Prepaid asset	33,400	62,700	33,400
Accrued Pension, SERP and PBOP \| Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Liability	$ 25,300	$ 25,800	$ 25,300
Minimum \| Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Expected long-term rate of return		8.25%
Compensation rate	3.50%	3.50%	3.50%
Minimum \| Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Expected long-term rate of return		8.25%
Maximum \| Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Compensation rate	4.00%	4.00%	4.00%
Pre-65 Plan \| Minimum \| Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Health care trend rate		3.50%
Pre-65 Plan \| Minimum \| Other Postretirement Benefits Plan \| Aquarion
Defined Contribution Plan Disclosure [Line Items]
Health care trend rate		3.50%
Pre-65 Plan \| Maximum \| Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Health care trend rate		6.50%
Pre-65 Plan \| Maximum \| Other Postretirement Benefits Plan \| Aquarion
Defined Contribution Plan Disclosure [Line Items]
Health care trend rate		6.75%
Post-65 Plan \| Minimum \| Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Health care trend rate		3.50%
Post-65 Plan \| Minimum \| Other Postretirement Benefits Plan \| Aquarion
Defined Contribution Plan Disclosure [Line Items]
Health care trend rate			7.00%
Post-65 Plan \| Maximum \| Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Health care trend rate		5.00%
Eversource Service Pension and PBOP Plans
Defined Contribution Plan Disclosure [Line Items]
Assumed rate of return		8.25%
Eversource PBOP Plan \| Other Postretirement Benefits Plan \| Equity Securities
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation		70.00%
Eversource PBOP Plan \| Other Postretirement Benefits Plan \| Fixed-Income Securities
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation		30.00%
Aquarion Plans
Defined Contribution Plan Disclosure [Line Items]
Assumed rate of return		7.00%
Aquarion Pension Plan \| Pension Plan \| Equity Securities
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation		54.00%
Aquarion Pension Plan \| Pension Plan \| Debt Securities
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation		36.00%
Aquarion Pension Plan \| Pension Plan \| Other Securities
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation		10.00%
Aquarion PBOP Plan \| Other Postretirement Benefits Plan \| Equity Securities
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation		54.00%
Aquarion PBOP Plan \| Other Postretirement Benefits Plan \| Debt Securities
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation		41.00%
Aquarion PBOP Plan \| Other Postretirement Benefits Plan \| Other Securities
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation		5.00%

EMPLOYEE BENEFITS - Schedule _2

EMPLOYEE BENEFITS - Schedule of Funded Status (Details) - Pension Plan - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 5,963.4	$ 5,070.8
CL&P
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	1,205.4	1,031
NSTAR Electric
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	1,340.8	1,144.7
PSNH
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 646.7	$ 543.1

EMPLOYEE BENEFITS - Schedule _3

EMPLOYEE BENEFITS - Schedule of Actuarial Assumptions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Compensation/Progression Rate		4.00%
Pension Plan \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.04%	4.22%
Compensation/Progression Rate	3.50%	3.50%
Pension Plan \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.35%	4.45%
Compensation/Progression Rate	4.00%	4.00%
Other Postretirement Benefits Plan \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.26%	4.38%
Other Postretirement Benefits Plan \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.28%	4.41%
Pre-65 Plan \| Other Postretirement Benefits Plan \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Health care trend rate	3.50%
Pre-65 Plan \| Other Postretirement Benefits Plan \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Health care trend rate	6.50%
Post-65 Plan \| Other Postretirement Benefits Plan \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Health care trend rate	3.50%
Post-65 Plan \| Other Postretirement Benefits Plan \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Health care trend rate	5.00%

EMPLOYEE BENEFITS - Schedule _4

EMPLOYEE BENEFITS - Schedule of Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 67.7	$ 84.8	$ 71.3
Interest Cost	219	196.4	188
Expected Return on Plan Assets	(367.1)	(391.6)	(334.1)
Actuarial Loss	143.2	145.7	135.2
Prior Service Cost/(Credit)	0.9	4.3	4.5
Total Net Periodic Benefit Income	63.7	39.6	64.9
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	7.8	10	9.5
Interest Cost	32.7	30.7	27.1
Expected Return on Plan Assets	(66.8)	(72.4)	(63.7)
Actuarial Loss	8.3	10.3	9.1
Prior Service Cost/(Credit)	(23.5)	(23.6)	(21.6)
Total Net Periodic Benefit Income	(41.5)	(45)	(39.6)
CL&P \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	18	21.4	18.5
Interest Cost	45.7	41.8	41.6
Expected Return on Plan Assets	(73.2)	(79.1)	(71.7)
Actuarial Loss	26.9	29.1	27.7
Prior Service Cost/(Credit)	0	1.1	1.5
Total Net Periodic Benefit Income	17.4	14.3	17.6
Intercompany Allocations	8.5	6.1	9.8
CL&P \| Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1.4	1.9	1.9
Interest Cost	6.3	5.8	5.3
Expected Return on Plan Assets	(9.2)	(10.4)	(9.7)
Actuarial Loss	1.3	1.6	1
Prior Service Cost/(Credit)	1.1	1.1	1.1
Total Net Periodic Benefit Income	0.9	0	(0.4)
Intercompany Allocations	(0.9)	(1)	(0.7)
NSTAR Electric \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	14.6	17.4	15.5
Interest Cost	49	43.5	42.7
Expected Return on Plan Assets	(97.1)	(104.9)	(87.6)
Actuarial Loss	44.7	41.1	41.1
Prior Service Cost/(Credit)	0.3	0.2	0.6
Total Net Periodic Benefit Income	11.5	(2.7)	12.3
Intercompany Allocations	8	6.5	9.1
NSTAR Electric \| Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1.7	2	1.7
Interest Cost	9.5	8.7	8.7
Expected Return on Plan Assets	(30.2)	(32.5)	(28.6)
Actuarial Loss	3.3	2.3	3.4
Prior Service Cost/(Credit)	(16.9)	(16.9)	(17)
Total Net Periodic Benefit Income	(32.6)	(36.4)	(31.8)
Intercompany Allocations	(1.2)	(1.3)	(1.1)
PSNH \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	7.1	11.2	9.7
Interest Cost	24	22	21.2
Expected Return on Plan Assets	(40.7)	(43.6)	(40)
Actuarial Loss	10.6	11.6	11.6
Prior Service Cost/(Credit)	0	0.4	0.5
Total Net Periodic Benefit Income	1	1.6	3
Intercompany Allocations	2.3	1.9	3.3
PSNH \| Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.7	1.1	1.3
Interest Cost	3.4	3.4	3
Expected Return on Plan Assets	(5.4)	(6)	(5.5)
Actuarial Loss	0.3	0.7	0.6
Prior Service Cost/(Credit)	0.4	0.5	0.6
Total Net Periodic Benefit Income	(0.6)	(0.3)	0
Intercompany Allocations	$ (0.4)	$ (0.4)	$ (0.5)

EMPLOYEE BENEFITS - Schedule _5

EMPLOYEE BENEFITS - Schedule of Assumptions used To Calculate Pension and SERP and PBOP (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	7.00%	7.00%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return		8.25%	8.25%
Compensation/Progression Rate		3.50%	3.50%
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return		8.25%	8.25%
Minimum \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.63%	3.85%	3.20%
Expected Long-Term Rate of Return	8.25%
Compensation/Progression Rate	3.50%
Minimum \| Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.85%	3.28%	3.48%
Expected Long-Term Rate of Return	8.25%
Maximum \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.55%	4.62%	3.90%
Compensation/Progression Rate	4.00%	4.00%
Maximum \| Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.65%	3.94%	4.64%

EMPLOYEE BENEFITS - Summary of

EMPLOYEE BENEFITS - Summary of Changes in Plan Assets and Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension Plan
Net Regulatory Assets [Abstract]
Actuarial Losses/(Gains) Arising During the Year	$ 591.6	$ 48.6
Actuarial Losses Reclassified as Net Periodic Benefit Expense	(137.8)	(140.1)
Unamortized Securitized Stranded Costs	0	(36.7)
Prior Service Cost Arising During the Year	0	0
Prior Service (Cost)/Credit Reclassified as Net Periodic Benefit (Expense)/Income	(0.7)	(3.9)
Prior Service Cost Securitized as Stranded Costs	0	(0.1)
Actuarial Loss	2,261.4	1,807.6
Prior Service Cost	5.6	6.3
Expected Actuarial Loss Expense	190.3
Expected Prior Service Cost Expense	0.9
OCI
Actuarial Losses/(Gains) Arising During the Year	15.4	0.7
Actuarial Losses Reclassified as Net Periodic Benefit Expense	(5.4)	(5.6)
Actuarial Losses Securitized as Stranded Costs	0	0
Prior Service Cost Arising During the Year	0	0
Prior Service (Cost)/Credit Reclassified as Net Periodic Benefit (Expense)/Income	(0.2)	(0.4)
Prior Service Costs Securitized as Stranded Costs		0
Actuarial Loss	90.8	80.8
Prior Service Cost	0.9	1.1
Expected Actuarial Loss	7.2
Expected Prior Service Cost	0.2
Other Postretirement Benefits Plan
Net Regulatory Assets [Abstract]
Actuarial Losses/(Gains) Arising During the Year	4.6	6.4
Actuarial Losses Reclassified as Net Periodic Benefit Expense	(8)	(9.9)
Unamortized Securitized Stranded Costs	0	(0.8)
Prior Service Cost Arising During the Year	0	1.3
Prior Service (Cost)/Credit Reclassified as Net Periodic Benefit (Expense)/Income	25.1	23.6
Prior Service Cost Securitized as Stranded Costs	0	(1.3)
Actuarial Loss	203.9	207.3
Prior Service Cost	(172.5)	(197.6)
Expected Actuarial Loss Expense	8.3
Expected Prior Service Cost Expense	(21.4)
OCI
Actuarial Losses/(Gains) Arising During the Year	2.3	(1.2)
Actuarial Losses Reclassified as Net Periodic Benefit Expense	(0.3)	(0.4)
Actuarial Losses Securitized as Stranded Costs	0	0
Prior Service Cost Arising During the Year	0	0
Prior Service (Cost)/Credit Reclassified as Net Periodic Benefit (Expense)/Income	(1.6)	0
Prior Service Costs Securitized as Stranded Costs		0
Actuarial Loss	7	5
Prior Service Cost	1	$ 2.6
Expected Actuarial Loss	0.2
Expected Prior Service Cost	$ 0.2

EMPLOYEE BENEFITS - Schedule _6

EMPLOYEE BENEFITS - Schedule of Estimated Future Benefit Payments (Details) $ in Millions	Dec. 31, 2019USD ($)
Pension Plan
Defined Contribution Plan Disclosure [Line Items]
2020	$ 320.1
2021	328.7
2022	337.5
2023	346.5
2024	352.4
2025-2029	1,813.1
Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
2020	58.1
2021	57.9
2022	57.3
2023	56.8
2024	56.2
2025-2029	$ 264.7

EMPLOYEE BENEFITS - Schedule _7

EMPLOYEE BENEFITS - Schedule of Long-term Rates of Return on Pension and PBOP (Details)	Dec. 31, 2019	Dec. 31, 2018
United States
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	15.00%	15.00%
Assumed Rate of Return	8.50%	8.50%
Global
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	10.00%	10.00%
Assumed Rate of Return	8.75%	8.75%
Non-United States
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	8.00%	8.00%
Assumed Rate of Return	8.50%	8.50%
Emerging Markets
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	4.00%	4.00%
Assumed Rate of Return	10.00%	10.00%
Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	13.00%	13.00%
Assumed Rate of Return	4.00%	4.00%
Public High Yield Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	4.00%	4.00%
Assumed Rate of Return	6.50%	6.50%
Private Debt
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	15.00%	15.00%
Assumed Rate of Return	9.00%	9.00%
Private Equity
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	15.00%	15.00%
Assumed Rate of Return	12.00%	12.00%
Real Assets
Defined Contribution Plan Disclosure [Line Items]
Target Asset Allocation	16.00%	16.00%
Assumed Rate of Return	7.50%	7.50%

EMPLOYEE BENEFITS - Schedule _8

EMPLOYEE BENEFITS - Schedule of Asset Category (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 4,968.6	$ 4,573.9	$ 4,739.5
Uncategorized	4,159.1	4,046.4
Pension Plan \| Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	1,942.5	1,821.2
Uncategorized	1,349.9	1,377.8
Pension Plan \| Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	1,625.2	1,511.8
Uncategorized	1,222.8	1,265.5
Pension Plan \| Private Equity
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	988.3	840.1
Uncategorized	971.4	834
Pension Plan \| Real Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	673.7	632
Uncategorized	615	569.1
Pension Plan \| Total Assets Before 401
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	5,229.7	4,805.1
Pension Plan \| 401 PBOP Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	(261.1)	(231.2)
Pension Plan \| Fair Value, Inputs, Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	767.6	597.9
Pension Plan \| Fair Value, Inputs, Level 1 \| Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	592.6	443.4
Pension Plan \| Fair Value, Inputs, Level 1 \| Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	99.4	85.5
Pension Plan \| Fair Value, Inputs, Level 1 \| Private Equity
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	16.9	6.1
Pension Plan \| Fair Value, Inputs, Level 1 \| Real Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	58.7	62.9
Pension Plan \| Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	303	160.8
Pension Plan \| Level 2 \| Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	0	0
Pension Plan \| Level 2 \| Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	303	160.8
Pension Plan \| Level 2 \| Private Equity
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	0	0
Pension Plan \| Level 2 \| Real Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	0	0
Other Postretirement Benefits Plan
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	935.9	849.6	$ 922.2
Uncategorized	410.2	436.7
Other Postretirement Benefits Plan \| Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	345	302.4
Uncategorized	187	210.5
Other Postretirement Benefits Plan \| Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	203.5	185.3
Uncategorized	148.1	123
Other Postretirement Benefits Plan \| Private Equity
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	26.5	32.7
Uncategorized	26.5	32.7
Other Postretirement Benefits Plan \| Real Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	99.8	98
Uncategorized	48.6	70.5
Other Postretirement Benefits Plan \| Total Assets Before 401
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	674.8	618.4
Other Postretirement Benefits Plan \| 401 PBOP Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	261.1	231.2
Other Postretirement Benefits Plan \| Fair Value, Inputs, Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	225	141.4
Other Postretirement Benefits Plan \| Fair Value, Inputs, Level 1 \| Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	158	91.9
Other Postretirement Benefits Plan \| Fair Value, Inputs, Level 1 \| Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	15.8	22
Other Postretirement Benefits Plan \| Fair Value, Inputs, Level 1 \| Private Equity
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	0	0
Other Postretirement Benefits Plan \| Fair Value, Inputs, Level 1 \| Real Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	51.2	27.5
Other Postretirement Benefits Plan \| Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	39.6	40.3
Other Postretirement Benefits Plan \| Level 2 \| Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	0	0
Other Postretirement Benefits Plan \| Level 2 \| Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	39.6	40.3
Other Postretirement Benefits Plan \| Level 2 \| Private Equity
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	0	0
Other Postretirement Benefits Plan \| Level 2 \| Real Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 0	$ 0

EMPLOYEE BENEFITS - Defined Con

EMPLOYEE BENEFITS - Defined Contribution Plan Narrative (Details)	12 Months Ended
	Dec. 31, 2019
Defined Contribution Plan, 401K
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution (as a percentage)	100.00%
Percentage of employees' pay (up to)	3.00%
Defined Contribution Plan, Alternate Contribution 401K
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution (as a percentage)	50.00%
Percentage of employees' pay (up to)	8.00%

EMPLOYEE BENEFITS - Schedule _9

EMPLOYEE BENEFITS - Schedule of Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 41.6	$ 38.4	$ 34.5
CL&P
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	5.5	5	4.6
NSTAR Electric
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	10.3	9.7	8.5
PSNH
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 3.5	$ 3.3	$ 3.7

EMPLOYEE BENEFITS - Share-Based

EMPLOYEE BENEFITS - Share-Based Payments Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted in incentive plan (up to) (in shares)	6,700,000
Shares available for issuance under incentive plan (in shares)	3,302,526	3,720,650
Shares outstanding (in shares)	439,293
Weighted average grant date fair value of restricted stock units (in dollars per share)	$ 57.47
Total unrecognized compensation expense	$ 24.4
Tax effect on total share-based payments (in percentage)	25.00%
Excess tax benefit	$ 1.5	$ 1.5	$ 2.9
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	$ 67.91	$ 56.69	$ 55.97
Shares outstanding (in shares)		424,119
Weighted average shares outstanding (in dollars per share)	$ 63.06	$ 56.57
Restricted stock units available (in shares)	236,359
Restricted stock unit fully vested (in shares)	334,870
Additional restricted stock unit expected to vest (in shares)	417,328
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	$ 68.33	$ 56.77	$ 55.70
Shares outstanding (in shares)	427,894	366,995
Weighted average shares outstanding (in dollars per share)	$ 60.38	$ 56.17
Restricted stock units available (in shares)	88,664
Weighted average grant date fair value of restricted stock units (in dollars per share)	$ 58.13
Restricted stock unit fully vested (in shares)	59,013
CL&P
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense	$ 5.3
Period for recognition	1 year 8 months 44 days
NSTAR Electric
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense	$ 5.3
Period for recognition	1 year 9 months 14 days
Eversource
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition	1 year 9 months
PSNH
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense	$ 2.1
Period for recognition	1 year 9 months 10 days
Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of graded vesting schedule under long-term incentive program	3 years
Board Members
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of graded vesting schedule under long-term incentive program	1 year

EMPLOYEE BENEFITS - Summary o_2

EMPLOYEE BENEFITS - Summary of RSU and Share Transactions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock Units (RSUs)
Units
Beginning balance (in shares)	782,365
Granted (in shares)	271,144
Shares issued (in shares)	(263,219)
Forfeited (in shares)	(16,127)
Ending balance (in shares)	774,163	782,365
Weighted Average Grant-Date Fair Value
Beginning balance (in dollars per share)	$ 50.25
Granted (in dollars per share)	67.91	$ 56.69	$ 55.97
Shares issued (in dollars per share)	55.34
Forfeited (in dollars per share)	63.31
Ending balance (in dollars per share)	$ 54.43	$ 50.25
Performance Shares
Units
Beginning balance (in shares)	499,564
Granted (in shares)	165,022
Shares issued (in shares)	(162,959)
Forfeited (in shares)	(14,720)
Ending balance (in shares)	486,907	499,564
Weighted Average Grant-Date Fair Value
Beginning balance (in dollars per share)	$ 56.08
Granted (in dollars per share)	68.33	$ 56.77	$ 55.70
Shares issued (in dollars per share)	55.69
Forfeited (in dollars per share)	58.20
Ending balance (in dollars per share)	$ 60.30	$ 56.08

EMPLOYEE BENEFITS - Schedule_10

EMPLOYEE BENEFITS - Schedule of Compensation Expense and Income Tax Benefit (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	$ 27.3	$ 21.4	$ 19.7
Future Income Tax Benefit	7	5.4	8
CL&P
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	9.8	7.8	7
Future Income Tax Benefit	2.5	2	2.9
NSTAR Electric
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	9.7	7.7	7
Future Income Tax Benefit	2.5	1.9	2.8
PSNH
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	3.3	2.9	3.2
Future Income Tax Benefit	$ 0.8	$ 0.7	$ 1.3

EMPLOYEE BENEFITS - Schedule_11

EMPLOYEE BENEFITS - Schedule of Other Retirement Benefits (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarially-Determined Liability	$ 52	$ 49.1	$ 53.4
Other Retirement Benefits Expense	2.7	2.7	2.8
CL&P
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarially-Determined Liability	0.2	0.3	0.3
Other Retirement Benefits Expense	1	1.1	1
NSTAR Electric
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarially-Determined Liability	0.1	0.1	0.1
Other Retirement Benefits Expense	0.9	1.1	1
PSNH
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarially-Determined Liability	1.7	1.7	1.9
Other Retirement Benefits Expense	$ 0.4	$ 0.4	$ 0.5

INCOME TAXES - Components of In

INCOME TAXES - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current Income Taxes:
Federal	$ 56,900	$ 106,500	$ 58,900
State	10,500	10,600	31,600
Total Current	67,400	117,100	90,500
Deferred Income Taxes, Net:
Federal	138,400	122,600	433,000
State	71,400	52,200	58,600
Total Deferred	209,812	174,812	491,630
Investment Tax Credits, Net	(3,700)	(2,900)	(3,200)
Income Tax Expense	273,499	288,972	578,892
CL&P
Current Income Taxes:
Federal	68,400	54,200	50,900
State	15,400	20,900	17,400
Total Current	83,800	75,100	68,300
Deferred Income Taxes, Net:
Federal	35,200	48,500	123,900
State	18,800	6,400	(4,600)
Total Deferred	54,005	54,859	119,295
Investment Tax Credits, Net	(800)	(900)	(1,000)
Income Tax Expense	136,971	129,056	186,646
NSTAR Electric
Current Income Taxes:
Federal	82,600	79,300	107,800
State	18,200	30,000	25,600
Total Current	100,800	109,300	133,400
Deferred Income Taxes, Net:
Federal	100	27,900	88,100
State	27,000	13,500	22,400
Total Deferred	27,107	41,438	110,499
Investment Tax Credits, Net	(2,600)	(1,800)	(1,800)
Income Tax Expense	125,313	148,906	242,085
PSNH
Current Income Taxes:
Federal	22,900	12,200	18,600
State	2,200	(500)	6,200
Total Current	25,100	11,700	24,800
Deferred Income Taxes, Net:
Federal	5,800	15,400	52,700
State	10,100	20,500	11,200
Total Deferred	15,917	35,924	63,883
Investment Tax Credits, Net	0	0	0
Income Tax Expense	$ 40,975	$ 47,576	$ 88,675

INCOME TAXES - Reconciliation B

INCOME TAXES - Reconciliation Between Income Tax Expense and Expected Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Income Before Income Tax Expense	$ 1,190,071	$ 1,329,491	$ 1,574,407
Statutory Federal Income Tax Expense at 21% in 2019 and 2018, and 35% in 2017	249,900	279,200	551,000
Tax Effect of Differences:
Depreciation	1,900	(30,800)	(10,800)
Investment Tax Credit Amortization	(3,700)	(2,900)	(3,200)
State Income Taxes, Net of Federal Impact	24,600	44,400	47,700
Dividends on ESOP	(5,100)	(5,100)	(8,400)
Tax Asset Valuation Allowance/Reserve Adjustments	40,100	5,200	7,000
Excess Stock Benefit	(1,500)	(1,500)	(2,900)
EDIT Amortization	(37,400)	(5,000)	0
Other, Net	4,700	5,500	(1,500)
Income Tax Expense	$ 273,499	$ 288,972	$ 578,892
Effective Tax Rate	23.00%	21.70%	36.80%
CL&P
Income Tax Contingency [Line Items]
Income Before Income Tax Expense	$ 547,823	$ 506,773	$ 563,372
Statutory Federal Income Tax Expense at 21% in 2019 and 2018, and 35% in 2017	115,000	106,400	197,200
Tax Effect of Differences:
Depreciation	(200)	(1,200)	(5,200)
Investment Tax Credit Amortization	(800)	(900)	(1,000)
State Income Taxes, Net of Federal Impact	2,500	14,500	4,500
Tax Asset Valuation Allowance/Reserve Adjustments	24,500	7,100	(9,500)
Excess Stock Benefit	(500)	(100)	(700)
EDIT Amortization	(5,800)	0	0
Other, Net	2,300	3,300	1,300
Income Tax Expense	$ 136,971	$ 129,056	$ 186,646
Effective Tax Rate	25.00%	25.50%	33.10%
NSTAR Electric
Income Tax Contingency [Line Items]
Income Before Income Tax Expense	$ 557,269	$ 531,996	$ 616,811
Statutory Federal Income Tax Expense at 21% in 2019 and 2018, and 35% in 2017	117,000	111,700	215,900
Tax Effect of Differences:
Depreciation	(3,000)	(2,800)	(3,000)
Investment Tax Credit Amortization	(2,600)	(1,800)	(1,800)
State Income Taxes, Net of Federal Impact	35,700	33,200	31,200
Tax Asset Valuation Allowance/Reserve Adjustments	0	1,200	0
Excess Stock Benefit	(500)	(100)	(700)
EDIT Amortization	(22,900)	0	0
Other, Net	1,600	7,500	500
Income Tax Expense	$ 125,313	$ 148,906	$ 242,085
Effective Tax Rate	22.50%	28.00%	39.20%
PSNH
Income Tax Contingency [Line Items]
Income Before Income Tax Expense	$ 175,023	$ 163,452	$ 224,671
Statutory Federal Income Tax Expense at 21% in 2019 and 2018, and 35% in 2017	36,800	34,300	78,600
Tax Effect of Differences:
Depreciation	(800)	100	1,100
Investment Tax Credit Amortization	0	0	0
State Income Taxes, Net of Federal Impact	9,800	15,800	11,300
Tax Asset Valuation Allowance/Reserve Adjustments	0	0	0
Excess Stock Benefit	(200)	(100)	(300)
EDIT Amortization	(4,000)	(4,400)	0
Other, Net	(600)	1,900	(2,000)
Income Tax Expense	$ 40,975	$ 47,576	$ 88,675
Effective Tax Rate	23.40%	29.10%	39.50%

INCOME TAXES - Temporary Differ

INCOME TAXES - Temporary Differences That Give Rise To Accumulated Deferred Income Tax Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets:
Employee Benefits	$ 509.4	$ 388.2
Derivative Liabilities	105	111.4
Regulatory Deferrals - Liabilities	267	299.3
Allowance for Uncollectible Accounts	56.7	54
Tax Effect - Tax Regulatory Liabilities	830.4	830.3
Federal Net Operating Loss Carryforwards	9.1	28.5
Purchase Accounting Adjustment	58.7	64.2
Other	190.4	166.2
Total Deferred Tax Assets	2,026.7	1,942.1
Less: Valuation Allowance	43	19.5
Net Deferred Tax Assets	1,983.7	1,922.6
Deferred Tax Liabilities:
Accelerated Depreciation and Other Plant-Related Differences	3,901	3,724.2
Property Tax Accruals	76.8	73.2
Regulatory Amounts:
Regulatory Deferrals - Assets	1,155.6	1,025.9
Tax Effect - Tax Regulatory Assets	238.2	238.9
Goodwill Regulatory Asset - 1999 Merger	90.6	95.2
Derivative Assets	19.7	20.1
Other	257.6	251.1
Total Deferred Tax Liabilities	5,739.5	5,428.6
Regulatory liabilities	4,019.2	3,979.7
Refunds to customers	51.5
EDIT due to Tax Cuts and Jobs Act
Regulatory Amounts:
Regulatory liabilities	2,844.6	2,883
CL&P
Deferred Tax Assets:
Employee Benefits	125.4	94.5
Derivative Liabilities	103.6	111.4
Regulatory Deferrals - Liabilities	37.1	38.6
Allowance for Uncollectible Accounts	25.7	23.1
Tax Effect - Tax Regulatory Liabilities	333.5	336.8
Federal Net Operating Loss Carryforwards	0	0
Purchase Accounting Adjustment	0	0
Other	92	81.1
Total Deferred Tax Assets	717.3	685.5
Less: Valuation Allowance	24.9	10.7
Net Deferred Tax Assets	692.4	674.8
Deferred Tax Liabilities:
Accelerated Depreciation and Other Plant-Related Differences	1,362.2	1,293.3
Property Tax Accruals	36.8	35.4
Regulatory Amounts:
Regulatory Deferrals - Assets	340.7	320.1
Tax Effect - Tax Regulatory Assets	171.7	167
Goodwill Regulatory Asset - 1999 Merger	0	0
Derivative Assets	19.7	19.9
Other	5.9	5.9
Total Deferred Tax Liabilities	1,937	1,841.6
Regulatory liabilities	1,247.8	1,231.8
Refunds to customers	7.9
CL&P \| EDIT due to Tax Cuts and Jobs Act
Regulatory Amounts:
Regulatory liabilities	1,022.8	1,031
NSTAR Electric
Deferred Tax Assets:
Employee Benefits	54.8	35
Derivative Liabilities	0	0
Regulatory Deferrals - Liabilities	165.7	195.5
Allowance for Uncollectible Accounts	17.7	17.8
Tax Effect - Tax Regulatory Liabilities	280.9	288.9
Federal Net Operating Loss Carryforwards	0	0
Purchase Accounting Adjustment	0	0
Other	35.8	15.6
Total Deferred Tax Assets	554.9	552.8
Less: Valuation Allowance	0	0
Net Deferred Tax Assets	554.9	552.8
Deferred Tax Liabilities:
Accelerated Depreciation and Other Plant-Related Differences	1,391.9	1,342.4
Property Tax Accruals	29	26.3
Regulatory Amounts:
Regulatory Deferrals - Assets	276.2	277.4
Tax Effect - Tax Regulatory Assets	11.7	9.7
Goodwill Regulatory Asset - 1999 Merger	77.8	81.7
Derivative Assets	0	0
Other	125.6	109.8
Total Deferred Tax Liabilities	1,912.2	1,847.3
Regulatory liabilities	1,725.8	1,703.9
Refunds to customers	31.5
NSTAR Electric \| EDIT due to Tax Cuts and Jobs Act
Regulatory Amounts:
Regulatory liabilities	1,071.2	1,103.7
PSNH
Deferred Tax Assets:
Employee Benefits	46.7	31.1
Derivative Liabilities	0	0
Regulatory Deferrals - Liabilities	19	16.1
Allowance for Uncollectible Accounts	2.8	3
Tax Effect - Tax Regulatory Liabilities	111.3	111.7
Federal Net Operating Loss Carryforwards	0	0.6
Purchase Accounting Adjustment	0	0
Other	20	33.4
Total Deferred Tax Assets	199.8	195.9
Less: Valuation Allowance	0	0
Net Deferred Tax Assets	199.8	195.9
Deferred Tax Liabilities:
Accelerated Depreciation and Other Plant-Related Differences	428.9	410.6
Property Tax Accruals	4.7	5.2
Regulatory Amounts:
Regulatory Deferrals - Assets	260.9	213.8
Tax Effect - Tax Regulatory Assets	8.3	8.1
Goodwill Regulatory Asset - 1999 Merger	0	0
Derivative Assets	0	0
Other	3.2	39.4
Total Deferred Tax Liabilities	706	677.1
Regulatory liabilities	479.2	483.6
Refunds to customers	5.6
PSNH \| EDIT due to Tax Cuts and Jobs Act
Regulatory Amounts:
Regulatory liabilities	392.8	$ 396.4
Yankee Gas Services Company
Regulatory Amounts:
Refunds to customers	1.4
NSTAR Gas
Regulatory Amounts:
Refunds to customers	$ 5.1

INCOME TAXES - Tax Credits and

INCOME TAXES - Tax Credits and Loss Carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Federal and State Tax Credit	$ 19.8	$ 103.6
Federal and State Charitable Contribution	0	2.2
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Federal and State Tax Credit	168.1	148.9
Federal and State Charitable Contribution	9.9	9.6
Operating Loss Carryforwards	65.5	80.7
CL&P \| Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Federal and State Tax Credit	0	0
Federal and State Charitable Contribution	0	0
CL&P \| State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Federal and State Tax Credit	122.3	107
Federal and State Charitable Contribution	0	0
Operating Loss Carryforwards	0	0
NSTAR Electric \| Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Federal and State Tax Credit	0	0
Federal and State Charitable Contribution	0	0
NSTAR Electric \| State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Federal and State Tax Credit	0	0
Federal and State Charitable Contribution	0	0
Operating Loss Carryforwards	0	0
PSNH \| Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Federal and State Tax Credit	0	0
Federal and State Charitable Contribution	0	0
PSNH \| State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Federal and State Tax Credit	0	0
Federal and State Charitable Contribution	0	0
Operating Loss Carryforwards	$ 0	$ 0

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - State and Local Jurisdiction - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Valuation allowance for tax credit and operating loss carryforward	$ 43	$ 19.5
Eversource
Operating Loss Carryforwards [Line Items]
Change in valuation allowance	18.5	5.2
CL&P
Operating Loss Carryforwards [Line Items]
Change in valuation allowance	$ 14.2	$ 4.4

INCOME TAXES - Reconciliation o

INCOME TAXES - Reconciliation of Unrecognized Tax Benefit (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 45.9	$ 51.7	$ 48.4
Gross Increases - Current Year	12.1	9.2	11.4
Gross Decreases - Prior Year		(6.5)	(0.9)
Gross Increases - Prior Year	3.4
Lapse of Statute of Limitations	(6.4)	(8.5)	(7.2)
Ending Balance	55	45.9	51.7
CL&P
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	18.2	18.1	15.3
Gross Increases - Current Year	4	3.2	4.7
Gross Decreases - Prior Year		(0.9)	(0.5)
Gross Increases - Prior Year	3.3
Lapse of Statute of Limitations	(2.4)	(2.2)	(1.4)
Ending Balance	$ 23.1	$ 18.2	$ 18.1

INCOME TAXES - Interest Expense

INCOME TAXES - Interest Expense and Accrued Interest Payable on Uncertain Tax Positions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Other Interest Expense/(Income)	$ 0	$ (1.7)	$ 0
Accrued Interest Expense	$ 0.1	$ 0.1

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Schedule of Reconciliation of Activity in Environmental Reserve (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accrual for Environmental Loss Contingencies [Roll Forward]
Accrual for Environmental Loss Contingencies, Beginning Balance	$ 64.7	$ 54.9
Additions	26.5	23.5
Payments/Reductions	(10.2)	(13.7)
Accrual for Environmental Loss Contingencies, Ending Balance	81	64.7
CL&P
Accrual for Environmental Loss Contingencies [Roll Forward]
Accrual for Environmental Loss Contingencies, Beginning Balance	5.4	4.7
Additions	7	1.9
Payments/Reductions	(1)	(1.2)
Accrual for Environmental Loss Contingencies, Ending Balance	11.4	5.4
NSTAR Electric
Accrual for Environmental Loss Contingencies [Roll Forward]
Accrual for Environmental Loss Contingencies, Beginning Balance	10.9	2.7
Additions	0.5	9.7
Payments/Reductions	(3.4)	(1.5)
Accrual for Environmental Loss Contingencies, Ending Balance	8	10.9
PSNH
Accrual for Environmental Loss Contingencies [Roll Forward]
Accrual for Environmental Loss Contingencies, Beginning Balance	5.4	5.7
Additions	2.8	0
Payments/Reductions	(0.7)	(0.3)
Accrual for Environmental Loss Contingencies, Ending Balance	$ 7.5	$ 5.4

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Schedule of Number of Sites and Reserves (Details) - site	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Number of Sites	57	60
CL&P
Loss Contingencies [Line Items]
Number of Sites	15	15
NSTAR Electric
Loss Contingencies [Line Items]
Number of Sites	15	16
PSNH
Loss Contingencies [Line Items]
Number of Sites	9	9

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Environmental Matters Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)site	Dec. 31, 2018USD ($)site	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Number of sites \| site	57	60
Reserve	$ 81	$ 64.7	$ 54.9
CL&P
Loss Contingencies [Line Items]
Number of sites \| site	15	15
Reserve	$ 11.4	$ 5.4	4.7
NSTAR Electric
Loss Contingencies [Line Items]
Number of sites \| site	15	16
Reserve	$ 8	$ 10.9	2.7
PSNH
Loss Contingencies [Line Items]
Number of sites \| site	9	9
Reserve	$ 7.5	$ 5.4	$ 5.7
MGP Site accrual
Loss Contingencies [Line Items]
Reserve balances related to former MGP sites	$ 67.9	$ 50.1
Environmental Sites for Which a Range of Loss Exists
Loss Contingencies [Line Items]
Number of sites \| site	6
Reserve	$ 35.9
Best estimate of potential remediation costs (up to)	$ 35
Environmental Sites for Which a Range of Loss Exists \| CL&P
Loss Contingencies [Line Items]
Number of sites \| site	1
Reserve	$ 0.4
Best estimate of potential remediation costs (up to)	$ 0.5
Environmental Site for Which a Range is Too Early to Determine
Loss Contingencies [Line Items]
Number of sites \| site	15
Reserve	$ 7.4
Environmental Site for Which a Range is Too Early to Determine \| CL&P
Loss Contingencies [Line Items]
Number of sites \| site	7
Reserve	$ 2.3
Environmental Site for Which a Range is Too Early to Determine \| NSTAR Electric
Loss Contingencies [Line Items]
Number of sites \| site	4
Reserve	$ 1.9
Evironmental Sites with Best Estimate
Loss Contingencies [Line Items]
Number of sites \| site	36
Reserve	$ 37.7
Evironmental Sites with Best Estimate \| CL&P
Loss Contingencies [Line Items]
Reserve	$ 8.7
Environmental site quantity remaining \| site	7
Evironmental Sites with Best Estimate \| NSTAR Electric
Loss Contingencies [Line Items]
Reserve	$ 6.1
Environmental site quantity remaining \| site	11
Evironmental Sites with Best Estimate \| PSNH
Loss Contingencies [Line Items]
Reserve	$ 7.5
Environmental site quantity remaining \| site	9

COMMITMENTS AND CONTINGENCIES_4

COMMITMENTS AND CONTINGENCIES - Schedule of Estimated Future Annual Costs of Long term Contractual Agreement (Details) $ in Millions	Dec. 31, 2019USD ($)
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	$ 998.8
2021	941.6
2022	946.5
2023	897.5
2024	881.9
Thereafter	4,785.2
Total	9,451.5
Renewable Energy
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	614.6
2021	594.3
2022	651.7
2023	629.1
2024	624.8
Thereafter	3,590.6
Total	6,705.1
Purchased Power and Capacity
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	73.5
2021	69
2022	75.1
2023	81.6
2024	75.9
Thereafter	71.5
Total	446.6
Peaker CfDs
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	22.4
2021	23
2022	16.9
2023	20.1
2024	15.5
Thereafter	29.8
Total	127.7
Natural Gas Procurement
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	266.2
2021	255.3
2022	202.8
2023	166.7
2024	165.7
Thereafter	1,093.3
Total	2,150
Transmission Support Commitments
Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract]
2020	22.1
2021	0
2022	0
2023	0
2024	0
Thereafter	0
Total	22.1
CL&P
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	558.2
2021	547.9
2022	602.7
2023	614.3
2024	605.8
Thereafter	2,875.9
Total	5,804.8
CL&P \| Renewable Energy
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	457.3
2021	459.6
2022	514.4
2023	516.2
2024	517.4
Thereafter	2,790.6
Total	5,255.5
CL&P \| Purchased Power and Capacity
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	69.8
2021	65.3
2022	71.4
2023	78
2024	72.9
Thereafter	55.5
Total	412.9
CL&P \| Peaker CfDs
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	22.4
2021	23
2022	16.9
2023	20.1
2024	15.5
Thereafter	29.8
Total	127.7
CL&P \| Transmission Support Commitments
Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract]
2020	8.7
2021	0
2022	0
2023	0
2024	0
Thereafter	0
Total	8.7
NSTAR Electric
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	107.3
2021	94.3
2022	94.5
2023	69.6
2024	66.8
Thereafter	434.1
Total	866.6
NSTAR Electric \| Renewable Energy
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	95.5
2021	91.2
2022	91.4
2023	66.6
2024	63.8
Thereafter	418.1
Total	826.6
NSTAR Electric \| Purchased Power and Capacity
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	3.1
2021	3.1
2022	3.1
2023	3
2024	3
Thereafter	16
Total	31.3
NSTAR Electric \| Transmission Support Commitments
Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract]
2020	8.7
2021	0
2022	0
2023	0
2024	0
Thereafter	0
Total	8.7
PSNH
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	67.1
2021	44.1
2022	46.5
2023	46.9
2024	43.6
Thereafter	381.9
Total	630.1
PSNH \| Renewable Energy
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	61.8
2021	43.5
2022	45.9
2023	46.3
2024	43.6
Thereafter	381.9
Total	623
PSNH \| Purchased Power and Capacity
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2020	0.6
2021	0.6
2022	0.6
2023	0.6
2024	0
Thereafter	0
Total	2.4
PSNH \| Transmission Support Commitments
Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract]
2020	4.7
2021	0
2022	0
2023	0
2024	0
Thereafter	0
Total	$ 4.7

COMMITMENTS AND CONTINGENCIES_5

COMMITMENTS AND CONTINGENCIES - Long-Term Contractual Arrangement Narrative (Details) MWh in Millions, $ in Millions	Nov. 22, 2019megawatt	Mar. 15, 2019megawatt	Dec. 28, 2018MWh	Dec. 31, 2019USD ($)contractprojectMW	Dec. 31, 2008contractMW	Dec. 31, 2018MW
Long-term Purchase Commitment [Line Items]
Estimated cost of energy purchase contracts				$ 9,451.5
Number of capacity contracts for differences between CL&P and UI \| contract				3
Amount of capacity contracts for differences between CL&P and UI (in MW) \| MW				676		787
Number of generation projects between CL&P and United Illuminated Company \| project				2
Number of demand response projects between CL&P and United Illuminated Company \| project				1
Percentage of costs and benefits borne by United Illuminated Company				20.00%
Peaker Contracts For Differences
Long-term Purchase Commitment [Line Items]
Estimated cost of energy purchase contracts				$ 127.7
Percentage of costs and benefits borne by United Illuminated Company					20.00%
Period of payment to generation facility owner					30 years
CL&P
Long-term Purchase Commitment [Line Items]
Estimated cost of energy purchase contracts				5,804.8
CL&P \| Peaker Contracts For Differences
Long-term Purchase Commitment [Line Items]
Estimated cost of energy purchase contracts				$ 127.7
Number of capacity contracts \| contract					3
Amount of peaking capacity contracts (in MW) \| MW					500
Percentage of costs and benefits borne					80.00%
CL&P, NSTAR Electric and PSNH \| Transmission Support Commitments
Long-term Purchase Commitment [Line Items]
Period of payment of annual operation and maintenance expense				30 years
Millstone Nuclear Power Station and Seabrook Nuclear Power Plant
Long-term Purchase Commitment [Line Items]
Estimated cost of energy purchase contracts				$ 4,100
Milestone Nuclear Power Station
Long-term Purchase Commitment [Line Items]
Annual purchase requirement (in MWh) \| MWh			9
Percent of the facility's output required to be purchased		50.00%
Nameplate capacity (in MW) \| megawatt		2,112
Milestone Nuclear Power Station \| CL&P
Long-term Purchase Commitment [Line Items]
Contract term		10 years	10 years
Percent of the facility's output required to be purchased		40.00%
Milestone Nuclear Power Station \| UI
Long-term Purchase Commitment [Line Items]
Contract term		10 years	10 years
Seabrook Nuclear Power Plant
Long-term Purchase Commitment [Line Items]
Percent of the facility's output required to be purchased	18.00%
Nameplate capacity (in MW) \| megawatt	1,250
Seabrook Nuclear Power Plant \| CL&P
Long-term Purchase Commitment [Line Items]
Contract term	8 years		8 years
Percent of the facility's output required to be purchased	15.00%
Seabrook Nuclear Power Plant \| UI
Long-term Purchase Commitment [Line Items]
Contract term	8 years		8 years

COMMITMENTS AND CONTINGENCIES_6

COMMITMENTS AND CONTINGENCIES - Schedule of Total Costs Incurred (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Long-term Purchase Commitment [Line Items]
Renewable Energy	$ 320.8	$ 218.5	$ 235.5
Purchased Power and Capacity	62.1	72	103.9
Peaker CfDs		20.9	38.7
Natural Gas Procurement	448.5	432.4	377
Transmission Support Commitments	21.8	23.4	19.8
Coal, Wood and Other	0	0	47.7
CL&P
Long-term Purchase Commitment [Line Items]
Renewable Energy	160.6	63.2	51
Purchased Power and Capacity	50.4	49.4	81
Peaker CfDs		20.9	38.7
Transmission Support Commitments	8.6	9.2	7.8
Coal, Wood and Other	0	0	0
NSTAR Electric
Long-term Purchase Commitment [Line Items]
Renewable Energy	89.9	89.8	123.7
Purchased Power and Capacity	5.1	4.4	4
Peaker CfDs	0	0	0
Transmission Support Commitments	8.6	9.2	7.8
Coal, Wood and Other	0	0	0
PSNH
Long-term Purchase Commitment [Line Items]
Renewable Energy	70.3	65.5	60.8
Purchased Power and Capacity	6.6	18.2	18.9
Peaker CfDs	0	0	0
Transmission Support Commitments	4.6	5	4.2
Coal, Wood and Other	$ 0	$ 0	$ 47.7

COMMITMENTS AND CONTINGENCIES_7

COMMITMENTS AND CONTINGENCIES - Spent Nuclear Fuel Obligations Narrative (Details) - USD ($) $ in Thousands	Jun. 12, 2019	Feb. 21, 2019	May 22, 2017	Dec. 31, 2019	Jul. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Guarantor Obligations [Line Items]
Net of damages awarded	$ 500
Remaining damages sought	$ 1,000
Damages paid					$ 500
DOE settlement payment				$ 29,000		$ (29,000)	$ (145,000)	$ 0
Yankee Companies
Guarantor Obligations [Line Items]
Damages sought			$ 104,400
YAEC
Guarantor Obligations [Line Items]
Net of damages awarded				2,800
Total amount of damages awarded				5,400
MYAPC
Guarantor Obligations [Line Items]
Net of damages awarded				5,000
Total amount of damages awarded				$ 21,000
CYAPC, YAEC, And MYAPC
Guarantor Obligations [Line Items]
Net of damages awarded		$ 103,200
CYAPC
Guarantor Obligations [Line Items]
Net of damages awarded		40,700
YAEC
Guarantor Obligations [Line Items]
Net of damages awarded		28,100
MYAPC
Guarantor Obligations [Line Items]
Net of damages awarded		$ 34,400

COMMITMENTS AND CONTINGENCIES_8

COMMITMENTS AND CONTINGENCIES - Guarantees and Obligations Narrative (Details)	Dec. 31, 2019USD ($)
Guarantee Of Financial Obligations Of Npt
Loss Contingencies [Line Items]
Maximum exposure	$ 25,000,000

COMMITMENTS AND CONTINGENCIES_9

COMMITMENTS AND CONTINGENCIES - Schedule of Guarantees and Indemnifications (Details) - USD ($) $ in Millions	Dec. 31, 2019	Oct. 25, 2019
Various - Surety Bonds
Guarantor Obligations [Line Items]
Maximum Exposure	$ 29.2
Rocky River Realty Company and Eversource Service - Lease Payments for Real Estate
Guarantor Obligations [Line Items]
Maximum Exposure	6.5
Bay State Wind LLC - Real Estate Purchase
Guarantor Obligations [Line Items]
Maximum Exposure	2.5
Sunrise Wind LLC - Offshore Wind
Guarantor Obligations [Line Items]
Maximum Exposure	$ 2.2
Sunrise Wind, LLC
Guarantor Obligations [Line Items]
Maximum Exposure		$ 15.4
Ownership interest		50.00%

COMMITMENTS AND CONTINGENCIE_10

COMMITMENTS AND CONTINGENCIES - FERC ROE Complaints (Details) $ in Millions	Oct. 16, 2018	Oct. 06, 2017	Apr. 29, 2016	Dec. 31, 2019USD ($)	Apr. 14, 2017	Oct. 15, 2014	Apr. 26, 2016complaint	Jul. 31, 2014complaint
Loss Contingencies [Line Items]
Percentage of base ROE reasonably justified	10.41%
Percentage of incentive cap on total ROE	13.08%
FERC ROE Complaints
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number \| complaint							4
Period of complaint				15 months
Basis point change				0.01%
Estimate of possible loss for each 10 basis point change to base ROE				$ 3
FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number \| complaint								3
Base ROE percentage challenged by complainants				11.14%
Percentage of ROE for any incentive project	13.08%
FERC ROE First Complaint
Loss Contingencies [Line Items]
Percentage of ROE for any incentive project					11.74%
Refund payments				$ 38.9
FERC ROE Second Complaint
Loss Contingencies [Line Items]
Percentage of base ROE of complaint period				10.57%	10.57%
Percentage of ROE for any incentive project				11.74%
Loss contingency, estimate of possible earnings impact				$ 39.1
FERC ROE Fourth Complaint
Loss Contingencies [Line Items]
Percentage of base ROE of complaint period			10.57%
Maximum percentage cap of ROE for incentive projects			11.74%
Percentage of ROE for any incentive project		10.57%
Original base ROE authorized by FERC at time of complaint		11.74%
CL&P \| FERC ROE First Complaint
Loss Contingencies [Line Items]
Refund payments				22.4
CL&P \| FERC ROE Second Complaint
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact				21.4
NSTAR Electric \| FERC ROE First Complaint
Loss Contingencies [Line Items]
Refund payments				13.7
NSTAR Electric \| FERC ROE Second Complaint
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact				14.6
PSNH \| FERC ROE First Complaint
Loss Contingencies [Line Items]
Refund payments				2.8
PSNH \| FERC ROE Second Complaint
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact				$ 3.1
Minimum \| FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Percentage of ROE for any incentive project						11.14%
Maximum \| FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Percentage of ROE for any incentive project						13.10%

COMMITMENTS AND CONTINGENCIE_11

COMMITMENTS AND CONTINGENCIES - Eversource and NSTAR Electric Boston Harbor Civil Action (Details) $ in Millions	Jul. 15, 2016kV	Dec. 31, 2019USD ($)kV	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Site Contingency [Line Items]
Amount of capacity required for installation of distribution cable (in kV) \| kV	115	115
Asset retirement obligations		$ 489.5	$ 466.2	$ 419.1
NSTAR Electric
Site Contingency [Line Items]
Base rate credit for new cable			17.5
Asset retirement obligations		97.5	$ 72.4	$ 44.6
Long-Term Derivative Liabilities
Site Contingency [Line Items]
Asset retirement obligations		32
Long-Term Derivative Liabilities \| NSTAR Electric
Site Contingency [Line Items]
Asset retirement obligations		$ 32

GENERATION ASSET SALE - Narrati

GENERATION ASSET SALE - Narrative (Details) - USD ($)	Nov. 27, 2019	Aug. 26, 2018	Jan. 10, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 08, 2018
Regulatory Assets [Line Items]
Proceeds from the sale of thermal assets				$ 0	$ 193,924,000	$ 0
Securitized Stranded Cost (included in Regulatory Assets)				5,514,700,000	5,145,900,000
Recoverable Divestiture Related Costs	$ 654,000,000
Pre-tax incmoe associated with generation assets				1,190,071,000	1,329,491,000	1,574,407,000
PSNH
Regulatory Assets [Line Items]
Purchase price in purchase sale agreement for thermal generation assets			$ 175,000,000
Proceeds from the sale of thermal assets			116,800,000	0	193,924,000	0
Purchase price in purchase sale agreement for hydroelectric assets		$ 5,800,000	$ 83,000,000
Proceeds from assets held for sale		77,200,000
Gain in sale of proceeds		17,300,000
Securitized Stranded Cost (included in Regulatory Assets)				945,800,000	929,500,000
Pre-tax incmoe associated with generation assets				175,023,000	163,452,000	224,671,000
Domestic Tax Authority \| PSNH
Regulatory Assets [Line Items]
Pre-tax incmoe associated with generation assets		$ 9,900,000				$ 60,000,000
Rate Reduction Bonds \| PSNH
Regulatory Assets [Line Items]
Amount of securitized rate reduction bonds issued							$ 635,700,000
Securitized Stranded Costs
Regulatory Assets [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)				565,300,000	608,400,000
Securitized Stranded Costs \| PSNH
Regulatory Assets [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)				565,300,000	608,400,000
Variable Interest Entity, Primary Beneficiary \| Securitized Stranded Costs \| PSNH
Regulatory Assets [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)				$ 565,300,000	$ 608,400,000

LEASES - Narrative (Details)

LEASES - Narrative (Details)	12 Months Ended
LEASES - Narrative (Details)	Dec. 31, 2019
Minimum
Lessee, Lease, Description [Line Items]
Renewal period	1 year
Maximum
Lessee, Lease, Description [Line Items]
Renewal period	20 years
CL&P \| Minimum
Lessee, Lease, Description [Line Items]
Renewal period	1 year
CL&P \| Maximum
Lessee, Lease, Description [Line Items]
Renewal period	20 years
NSTAR Electric \| Minimum
Lessee, Lease, Description [Line Items]
Renewal period	1 year
NSTAR Electric \| Maximum
Lessee, Lease, Description [Line Items]
Renewal period	20 years
PSNH \| Minimum
Lessee, Lease, Description [Line Items]
Renewal period	1 year
PSNH \| Maximum
Lessee, Lease, Description [Line Items]
Renewal period	20 years

LEASES - Components of Lease Co

LEASES - Components of Lease Cost (Details) $ in Millions	12 Months Ended
LEASES - Components of Lease Cost (Details) $ in Millions	Dec. 31, 2019USD ($)
Financing Lease Cost:
Amortization of Right-of-use-Assets	$ 1.7
Interest on Lease Liabilities	1.2
Total Finance Lease Cost	2.9
Operating Lease Cost	11.7
Variable Lease Cost	60.5
Total Lease Cost	75.1
CL&P
Financing Lease Cost:
Amortization of Right-of-use-Assets	0.7
Interest on Lease Liabilities	0.6
Total Finance Lease Cost	1.3
Operating Lease Cost	0.5
Variable Lease Cost	13.3
Total Lease Cost	15.1
NSTAR Electric
Financing Lease Cost:
Amortization of Right-of-use-Assets	0.2
Interest on Lease Liabilities	0.6
Total Finance Lease Cost	0.8
Operating Lease Cost	3.4
Variable Lease Cost	0
Total Lease Cost	4.2
PSNH
Financing Lease Cost:
Amortization of Right-of-use-Assets	0.1
Interest on Lease Liabilities	0
Total Finance Lease Cost	0.1
Operating Lease Cost	0.1
Variable Lease Cost	47.2
Total Lease Cost	$ 47.4

LEASES - Operating Leases Renta

LEASES - Operating Leases Rental Payments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating Leased Assets [Line Items]
Operating leases, rent expense	$ 10.8	$ 10.5
CL&P
Operating Leased Assets [Line Items]
Operating leases, rent expense	10.9	11.7
NSTAR Electric
Operating Leased Assets [Line Items]
Operating leases, rent expense	11.8	11.3
PSNH
Operating Leased Assets [Line Items]
Operating leases, rent expense	$ 2.5	$ 3.3

LEASES - Supplemental Balance S

LEASES - Supplemental Balance Sheet Information Related to Leases (Details) $ in Millions	Dec. 31, 2019USD ($)
Operating Leases:
Operating Lease Right-of-use-Assets, Net	$ 49.9
Operating Lease Liabilities - Current Portion	8.6
Operating Lease Liabilities - Long-Term	41.3
Total Operating Lease Liabilities	49.9
Finance Leases:
Finance Lease Right-of-use-Assets, Net	8.2
Finance Lease Liabilities - Current Portion	2.4
Finance Lease Liabilities - Long-Term	8.1
Total Finance Lease Liabilities	10.5
CL&P
Operating Leases:
Operating Lease Right-of-use-Assets, Net	0.7
Operating Lease Liabilities - Current Portion	0.5
Operating Lease Liabilities - Long-Term	0.2
Total Operating Lease Liabilities	0.7
Finance Leases:
Finance Lease Right-of-use-Assets, Net	1.9
Finance Lease Liabilities - Current Portion	1.6
Finance Lease Liabilities - Long-Term	1.4
Total Finance Lease Liabilities	3
NSTAR Electric
Operating Leases:
Operating Lease Right-of-use-Assets, Net	24.2
Operating Lease Liabilities - Current Portion	0.7
Operating Lease Liabilities - Long-Term	23.5
Total Operating Lease Liabilities	24.2
Finance Leases:
Finance Lease Right-of-use-Assets, Net	3.3
Finance Lease Liabilities - Current Portion	0
Finance Lease Liabilities - Long-Term	4.4
Total Finance Lease Liabilities	4.4
PSNH
Operating Leases:
Operating Lease Right-of-use-Assets, Net	0.4
Operating Lease Liabilities - Current Portion	0.1
Operating Lease Liabilities - Long-Term	0.3
Total Operating Lease Liabilities	0.4
Finance Leases:
Finance Lease Right-of-use-Assets, Net	0.9
Finance Lease Liabilities - Current Portion	0.1
Finance Lease Liabilities - Long-Term	0.8
Total Finance Lease Liabilities	$ 0.9

LEASES - Other Information Rela

LEASES - Other Information Related to Leases (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Weighted-Average Remaining Lease Term (Years):
Operating Leases	12 years
Finance Leases	12 years
Weighted-Average Discount Rate (Percentage):
Operating Leases	3.90%
Finance Leases	4.00%
Cash Paid for Amounts Included in the Measurement of Lease Liabilities:
Operating Cash Flows from Operating Leases	$ 11.4
Operating Cash Flows from Finance Leases	1.2
Financing Cash Flows from Finance Leases	2.6
Supplemental Non-Cash Information on Lease Liabilities:
Right-of-use-Assets Obtained in Exchange for New Operating Lease Liabilities	2.9
Right-of-use-Assets Obtained in Exchange for New Finance Lease Liabilities	$ 2
CL&P
Weighted-Average Remaining Lease Term (Years):
Operating Leases	2 years
Finance Leases	2 years
Weighted-Average Discount Rate (Percentage):
Operating Leases	2.50%
Finance Leases	10.50%
Cash Paid for Amounts Included in the Measurement of Lease Liabilities:
Operating Cash Flows from Operating Leases	$ 0.4
Operating Cash Flows from Finance Leases	0.6
Financing Cash Flows from Finance Leases	1.4
Supplemental Non-Cash Information on Lease Liabilities:
Right-of-use-Assets Obtained in Exchange for New Operating Lease Liabilities	1
Right-of-use-Assets Obtained in Exchange for New Finance Lease Liabilities	$ 0
NSTAR Electric
Weighted-Average Remaining Lease Term (Years):
Operating Leases	20 years
Finance Leases	22 years
Weighted-Average Discount Rate (Percentage):
Operating Leases	4.10%
Finance Leases	2.90%
Cash Paid for Amounts Included in the Measurement of Lease Liabilities:
Operating Cash Flows from Operating Leases	$ 1.6
Operating Cash Flows from Finance Leases	0.6
Financing Cash Flows from Finance Leases	0
Supplemental Non-Cash Information on Lease Liabilities:
Right-of-use-Assets Obtained in Exchange for New Operating Lease Liabilities	0.1
Right-of-use-Assets Obtained in Exchange for New Finance Lease Liabilities	$ 0
PSNH
Weighted-Average Remaining Lease Term (Years):
Operating Leases	9 years
Finance Leases	9 years
Weighted-Average Discount Rate (Percentage):
Operating Leases	3.70%
Finance Leases	3.50%
Cash Paid for Amounts Included in the Measurement of Lease Liabilities:
Operating Cash Flows from Operating Leases	$ 0.1
Operating Cash Flows from Finance Leases	0
Financing Cash Flows from Finance Leases	0.1
Supplemental Non-Cash Information on Lease Liabilities:
Right-of-use-Assets Obtained in Exchange for New Operating Lease Liabilities	0.2
Right-of-use-Assets Obtained in Exchange for New Finance Lease Liabilities	$ 0

LEASES - Future Minimum Lease P

LEASES - Future Minimum Lease Payments under Long-Term Leases (Details) $ in Millions	Dec. 31, 2019USD ($)
Operating Leases
2020	$ 10.2
2021	9
2022	7.4
2023	4.9
2024	2.8
Thereafter	28.9
Future lease payments	63.2
Less amount representing interest	13.3
Present value of future minimum lease payments	49.9
Finance Leases
2020	3.4
2021	2.9
2022	1.5
2023	0.8
2024	0.8
Thereafter	13.1
Future lease payments	22.5
Less amount representing interest	12
Present value of future minimum lease payments	10.5
CL&P
Operating Leases
2020	0.5
2021	0.2
2022	0
2023	0
2024	0
Thereafter	0.1
Future lease payments	0.8
Less amount representing interest	0.1
Present value of future minimum lease payments	0.7
Finance Leases
2020	2
2021	1.5
2022	0
2023	0
2024	0
Thereafter	0
Future lease payments	3.5
Less amount representing interest	0.5
Present value of future minimum lease payments	3
NSTAR Electric
Operating Leases
2020	1.8
2021	1.6
2022	1.6
2023	1.6
2024	1.7
Thereafter	28.7
Future lease payments	37
Less amount representing interest	12.8
Present value of future minimum lease payments	24.2
Finance Leases
2020	0.6
2021	0.6
2022	0.6
2023	0.6
2024	0.7
Thereafter	12.6
Future lease payments	15.7
Less amount representing interest	11.3
Present value of future minimum lease payments	4.4
PSNH
Operating Leases
2020	0.1
2021	0.1
2022	0.1
2023	0
2024	0
Thereafter	0.2
Future lease payments	0.5
Less amount representing interest	0.1
Present value of future minimum lease payments	0.4
Finance Leases
2020	0.1
2021	0.1
2022	0.1
2023	0.1
2024	0.1
Thereafter	0.5
Future lease payments	1
Less amount representing interest	0.1
Present value of future minimum lease payments	$ 0.9

LEASES - Future Minimum Rental

LEASES - Future Minimum Rental Payments under Operating Leases (Details) $ in Millions	Dec. 31, 2018USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 11.5
2020	9.8
2021	8.7
2022	7.2
2023	4.7
Thereafter	32.7
Future minimum lease payments	74.6
CL&P
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	1.5
2020	1.4
2021	1.2
2022	1.1
2023	0.5
Thereafter	0.2
Future minimum lease payments	5.9
NSTAR Electric
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	7.2
2020	6
2021	5.3
2022	4.4
2023	3.1
Thereafter	29.5
Future minimum lease payments	55.5
PSNH
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	0.5
2020	0.4
2021	0.4
2022	0.4
2023	0.2
Thereafter	0.3
Future minimum lease payments	$ 2.2

LEASES - Future Minimum Renta_2

LEASES - Future Minimum Rental Payments under Capital Leases (Details) $ in Millions	Dec. 31, 2018USD ($)
Capital Leased Assets [Line Items]
2019	$ 3.4
2020	3.4
2021	2.9
2022	1.5
2023	0.7
Thereafter	13.9
Future minimum lease payments	25.8
Less amount representing interest	13.8
Present value of future minimum lease payments	12
CL&P
Capital Leased Assets [Line Items]
2019	2
2020	2
2021	1.5
2022	0
2023	0
Thereafter	0
Future minimum lease payments	5.5
Less amount representing interest	1
Present value of future minimum lease payments	4.5
NSTAR Electric
Capital Leased Assets [Line Items]
2019	0.5
2020	0.5
2021	0.5
2022	0.6
2023	0.6
Thereafter	13.4
Future minimum lease payments	16.1
Less amount representing interest	12.4
Present value of future minimum lease payments	3.7
PSNH
Capital Leased Assets [Line Items]
2019	0.1
2020	0.1
2021	0.1
2022	0.1
2023	0.1
Thereafter	0.5
Future minimum lease payments	1
Less amount representing interest	0.1
Present value of future minimum lease payments	$ 0.9

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	$ 155,570	$ 155,570
Rate Reduction Bonds	540,122	583,331
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	155,600	155,600
Long-Term Debt	14,098,200	13,086,100
Rate Reduction Bonds	583,300	635,700
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	162,000	156,800
Long-Term Debt	15,170,200	13,154,900
Rate Reduction Bonds	625,900	645,800
CL&P
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	116,200	116,200
CL&P \| Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	116,200	116,200
Long-Term Debt	3,518,100	3,254,000
CL&P \| Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	117,800	113,800
Long-Term Debt	4,058,000	3,429,200
NSTAR Electric
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,000	43,000
NSTAR Electric \| Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,000	43,000
Long-Term Debt	3,342,100	2,944,800
NSTAR Electric \| Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	44,200	43,000
Long-Term Debt	3,659,900	3,024,100
PSNH
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Rate Reduction Bonds	540,122	583,331
PSNH \| Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	0	0
Long-Term Debt	951,600	805,200
Rate Reduction Bonds	583,300	635,700
PSNH \| Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	0	0
Long-Term Debt	1,005,700	819,500
Rate Reduction Bonds	$ 625,900	$ 645,800

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Schedule of Changes in AOCI By Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 11,486,817	$ 11,086,242
OCI Before Reclassifications	(12,100)	(200)
Amounts Reclassified from AOCI	7,000	6,600
Net OCI	(5,100)	6,400
Ending balance	12,629,994	11,486,817
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(60,000)	(66,403)
Ending balance	(65,059)	(60,000)
Qualified Cash Flow Hedging Instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(4,400)	(6,200)
OCI Before Reclassifications	0	0
Amounts Reclassified from AOCI	1,400	1,800
Net OCI	1,400	1,800
Ending balance	(3,000)	(4,400)
Unrealized Gains/(Losses) on Marketable Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(500)	0
OCI Before Reclassifications	1,200	(500)
Amounts Reclassified from AOCI	0	0
Net OCI	1,200	(500)
Ending balance	700	(500)
Defined Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(55,100)	(60,200)
OCI Before Reclassifications	(13,300)	300
Amounts Reclassified from AOCI	5,600	4,800
Net OCI	(7,700)	5,100
Ending balance	$ (62,800)	$ (55,100)

ACCUMULATED OTHER COMPREHENSI_4

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Related tax effect recognized in AOCI	$ 4.4	$ (0.2)	$ 4.1
Pre-tax amount reclassified from AOCI as a decrease to net income	2.5
Pre-tax amount reclassified from AOCI as a decrease to net income as a result of amortization of Pension, SERP and PBOP costs	7.8
NSTAR Gas
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax amount reclassified from AOCI as a decrease to net income	0.7
PSNH
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax amount reclassified from AOCI as a decrease to net income	$ 1.8

ACCUMULATED OTHER COMPREHENSI_5

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Schedule of Amounts Reclassified From AOCI By Component (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax Effect									$ (273,499)	$ (288,972)	$ (578,892)
Net Income Attributable to Common Shareholders	$ 250,000	$ 318,900	$ 31,500	$ 308,700	$ 231,300	$ 289,400	$ 242,800	$ 269,500	909,053	1,033,000	987,996
Defined Benefit Plan Costs:
Total Amounts Reclassified from AOCI, Net of Tax									7,000	6,600	6,500
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax Effect									1,100	1,000	1,300
Qualified Cash Flow Hedging Instruments, Net of Tax \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income Attributable to Common Shareholders									(1,400)	(1,800)	(2,000)
Amortization of Actuarial Losses
Defined Benefit Plan Costs:
Reclassifications from AOCI									(5,700)	(6,000)	(6,200)
Amortization of Prior Service Cost
Defined Benefit Plan Costs:
Reclassifications from AOCI									(1,800)	(400)	(1,100)
Defined Benefit Plans
Defined Benefit Plan Costs:
Reclassifications from AOCI									(7,500)	(6,400)	(7,300)
Tax Effect									1,900	1,600	2,800
Total Amounts Reclassified from AOCI, Net of Tax									(5,600)	(4,800)	(4,500)
Interest Expense \| Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Qualified Cash Flow Hedging Instruments									$ (2,500)	$ (2,800)	$ (3,300)

DIVIDEND RESTRICTIONS - Narrati

DIVIDEND RESTRICTIONS - Narrative (Details) $ in Millions	Dec. 31, 2019USD ($)
Schedule of Restrictions on Retained Earnings [Line Items]
Consolidated total debt to total capital ratio (as a percentage)	0.65
Retained earnings subject to restrictions	$ 4,200
CL&P
Schedule of Restrictions on Retained Earnings [Line Items]
Retained earnings subject to restrictions	1,800
NSTAR Electric
Schedule of Restrictions on Retained Earnings [Line Items]
Retained earnings subject to restrictions	2,300
PSNH
Schedule of Restrictions on Retained Earnings [Line Items]
Retained earnings subject to restrictions	$ 490.3

COMMON SHARES - Common Shares A

COMMON SHARES - Common Shares Authorized and Issued (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Per share par value (in dollars per share)	$ 5	$ 5
Authorized (in shares)	380,000,000	380,000,000
Issued (in shares)	345,858,402	333,878,402
CL&P
Class of Stock [Line Items]
Per share par value (in dollars per share)	$ 10	$ 10
Authorized (in shares)	24,500,000	24,500,000
Issued (in shares)	6,035,205	6,035,205
NSTAR Electric
Class of Stock [Line Items]
Per share par value (in dollars per share)	$ 1	$ 1
Authorized (in shares)	100,000,000	100,000,000
Issued (in shares)	200	200
PSNH
Class of Stock [Line Items]
Per share par value (in dollars per share)	$ 1	$ 1
Authorized (in shares)	100,000,000	100,000,000
Issued (in shares)	301	301

PREFERRED STOCK NOT SUBJECT T_3

PREFERRED STOCK NOT SUBJECT TO MANDATORY REDEMPTION - Narrative (Details)	Dec. 31, 2019$ / sharesshares
CL&P
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares) \| shares	9,000,000
Preferred stock, par value (in dollars per share) \| $ / shares	$ 50
NSTAR Electric
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares) \| shares	2,890,000
Preferred stock, par value (in dollars per share) \| $ / shares	$ 100

COMMON SHARES - Narrative (Deta

COMMON SHARES - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 30, 2019	Jun. 04, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Equity offering (in shares)		17,940,000
Common shares issued directly by the Company (in shares)		5,980,000	11,980,000
Common shares issuable pursuant to forward sale agreement (in shares)	6,000,000	11,960,000
Net proceeds from common shares issued directly by the Company	$ 425,400	$ 426,900	$ 852,254	$ 0	$ 0
Forward sale price (in dollars per share)	$ 71.48
Amount that would have been required to be paid if net settled			$ 84,400
Shares that would have been required to be delivered if net settled (in shares)			992,189
Treasury stock (in shares)			15,977,757	16,992,594
Common stock outstanding (in shares)			329,880,645	316,885,808

PREFERRED STOCK NOT SUBJECT T_4

PREFERRED STOCK NOT SUBJECT TO MANDATORY REDEMPTION - Schedule of Preferred Stock by Class (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Preferred stock value outstanding	$ 155.6	$ 155.6
CL&P
Class of Stock [Line Items]
Shares outstanding (in shares)	2,324,000	2,324,000
Preferred stock value outstanding	$ 116.2	$ 116.2
CL&P \| Series of 1947 Preferred Stock at $1.90
Class of Stock [Line Items]
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 1.90	$ 1.90
Redemption Price Per Share (in dollars per share)	$ 52.50
Shares outstanding (in shares)	163,912	163,912
Preferred stock value outstanding	$ 8.2	$ 8.2
CL&P \| Series of 1947 Preferred Stock at $2.00
Class of Stock [Line Items]
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 2	$ 2
Redemption Price Per Share (in dollars per share)	$ 54
Shares outstanding (in shares)	336,088	336,088
Preferred stock value outstanding	$ 16.8	$ 16.8
CL&P \| Series of 1949 Preferred Stock at $2.04
Class of Stock [Line Items]
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 2.04	$ 2.04
Redemption Price Per Share (in dollars per share)	$ 52
Shares outstanding (in shares)	100,000	100,000
Preferred stock value outstanding	$ 5	$ 5
CL&P \| Series of 1949 Preferred Stock at $2.20
Class of Stock [Line Items]
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 2.20	$ 2.20
Redemption Price Per Share (in dollars per share)	$ 52.50
Shares outstanding (in shares)	200,000	200,000
Preferred stock value outstanding	$ 10	$ 10
CL&P \| Series of 1949 Preferred Stock at 3.90%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	3.90%	3.90%
Redemption Price Per Share (in dollars per share)	$ 50.50
Shares outstanding (in shares)	160,000	160,000
Preferred stock value outstanding	$ 8	$ 8
CL&P \| Series E of 1954 Preferred Stock at $2.06
Class of Stock [Line Items]
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 2.06	$ 2.06
Redemption Price Per Share (in dollars per share)	$ 51
Shares outstanding (in shares)	200,000	200,000
Preferred stock value outstanding	$ 10	$ 10
CL&P \| Series F of 1955 Preferred Stock at $2.09
Class of Stock [Line Items]
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 2.09	$ 2.09
Redemption Price Per Share (in dollars per share)	$ 51
Shares outstanding (in shares)	100,000	100,000
Preferred stock value outstanding	$ 5	$ 5
CL&P \| Series of 1956 Preferred Stock at 4.5%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	4.50%	4.50%
Redemption Price Per Share (in dollars per share)	$ 50.75
Shares outstanding (in shares)	104,000	104,000
Preferred stock value outstanding	$ 5.2	$ 5.2
CL&P \| Series of 1958 Preferred Stock at 4.96%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	4.96%	4.96%
Redemption Price Per Share (in dollars per share)	$ 50.50
Shares outstanding (in shares)	100,000	100,000
Preferred stock value outstanding	$ 5	$ 5
CL&P \| Series of 1963 Preferred Stock at 4.5%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	4.50%	4.50%
Redemption Price Per Share (in dollars per share)	$ 50.50
Shares outstanding (in shares)	160,000	160,000
Preferred stock value outstanding	$ 8	$ 8
CL&P \| Series of 1967 Preferred Stock at 5.28%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	5.28%	5.28%
Redemption Price Per Share (in dollars per share)	$ 51.43
Shares outstanding (in shares)	200,000	200,000
Preferred stock value outstanding	$ 10	$ 10
CL&P \| Series G of 1968 Preferred Stock at $3.24
Class of Stock [Line Items]
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 3.24	$ 3.24
Redemption Price Per Share (in dollars per share)	$ 51.84
Shares outstanding (in shares)	300,000	300,000
Preferred stock value outstanding	$ 15	$ 15
CL&P \| Series of 1968 Preferred Stock at 6.56%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	6.56%	6.56%
Redemption Price Per Share (in dollars per share)	$ 51.44
Shares outstanding (in shares)	200,000	200,000
Preferred stock value outstanding	$ 10	$ 10
NSTAR Electric
Class of Stock [Line Items]
Shares outstanding (in shares)	430,000	430,000
Preferred stock value outstanding	$ 43	$ 43
NSTAR Electric \| Preferred Stock 4.25%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	4.25%	4.25%
Redemption Price Per Share (in dollars per share)	$ 103.625
Shares outstanding (in shares)	180,000	180,000
Preferred stock value outstanding	$ 18	$ 18
NSTAR Electric \| Preferred Stock 4.78%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	4.78%	4.78%
Redemption Price Per Share (in dollars per share)	$ 102.80
Shares outstanding (in shares)	250,000	250,000
Preferred stock value outstanding	$ 25	$ 25
Aquarion Water Company \| Series of Preferred Stock at 6%
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percentage)	6.00%	6.00%
Redemption Price Per Share (in dollars per share)	$ 100
Shares outstanding (in shares)	23	23
Preferred stock value outstanding	$ 0	$ 0
Fair Value Adjustment \| NSTAR Electric
Class of Stock [Line Items]
Preferred stock value outstanding	$ 3.6	$ 3.6

COMMON SHAREHOLDERS' EQUITY A_2

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Net income attributable to noncontrolling interests	$ 7,500	$ 7,500	$ 7,500
Noncontrolling interest - preferred stock of subsidiaries	$ 155,570	$ 155,570

EARNINGS PER SHARE - Components

EARNINGS PER SHARE - Components of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income Attributable to Common Shareholders	$ 250,000	$ 318,900	$ 31,500	$ 308,700	$ 231,300	$ 289,400	$ 242,800	$ 269,500	$ 909,053	$ 1,033,000	$ 987,996
Weighted Average Common Shares Outstanding:
Basic (in shares)									321,416,086	317,370,369	317,411,097
Dilutive Effect of:
Share-Based Compensation Awards and Other (in shares)									762,215	623,565	620,483
Equity Forward Sale Agreement (in shares)									763,335	0	0
Dilutive Effect (in shares)									1,525,550	623,565	620,483
Diluted (in shares)									322,941,636	317,993,934	318,031,580
Basic EPS (in dollars per share)	$ 0.77	$ 0.98	$ 0.10	$ 0.97	$ 0.73	$ 0.91	$ 0.76	$ 0.85	$ 2.83	$ 3.25	$ 3.11
Diluted EPS (in dollars per share)	$ 0.76	$ 0.98	$ 0.10	$ 0.97	$ 0.73	$ 0.91	$ 0.76	$ 0.85	$ 2.81	$ 3.25	$ 3.11

REVENUES (Details)

REVENUES (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
REVENUES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									$ 8,450,000	$ 8,472,700
Alternative Revenue Programs									53,200	(46,100)
Other Revenues									23,300	21,600
Operating Revenues	$ 2,050,400	$ 2,175,800	$ 1,884,500	$ 2,415,800	$ 2,034,900	$ 2,271,400	$ 1,853,900	$ 2,288,000	8,526,470	8,448,201	$ 7,751,952
Lease revenue									4,400
Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									4,411,100	4,439,800
Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									2,992,000	3,028,300
Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									421,600	442,300
Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									7,824,700	7,910,400
Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									269,400	264,000
Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									275,200	241,100
Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									76,000	81,500
Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									4,700	(24,300)
CL&P
Disaggregation of Revenue [Line Items]
Operating Revenues	788,700	853,900	740,800	849,200	751,300	865,000	694,900	785,000	3,232,551	3,096,174	2,887,359
Lease revenue									1,000
NSTAR Electric
Disaggregation of Revenue [Line Items]
Operating Revenues	686,400	878,700	681,900	797,600	712,600	939,500	690,700	770,100	3,044,642	3,112,926	2,980,629
Lease revenue									2,700
PSNH
Disaggregation of Revenue [Line Items]
Operating Revenues	$ 268,200	$ 280,400	$ 240,900	$ 276,400	$ 254,900	$ 290,200	$ 235,100	$ 267,400	1,065,936	1,047,619	981,624
Operating Segments \| Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									6,912,100	6,986,300
Alternative Revenue Programs									45,900	(47,000)
Other Revenues									18,500	17,900
Operating Revenues									6,976,500	6,957,200	5,542,900
Operating Segments \| Electric Distribution \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									3,723,700	3,766,600
Operating Segments \| Electric Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									2,584,800	2,634,700
Operating Segments \| Electric Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									331,800	351,900
Operating Segments \| Electric Distribution \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									6,640,300	6,753,200
Operating Segments \| Electric Distribution \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Electric Distribution \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									215,700	179,500
Operating Segments \| Electric Distribution \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									54,800	65,900
Operating Segments \| Electric Distribution \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,300	(12,300)
Operating Segments \| Natural Gas Distribution
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,064,000	1,020,300
Alternative Revenue Programs									(4,900)	(1,200)
Other Revenues									3,100	3,100
Operating Revenues									1,062,200	1,022,200	947,300
Operating Segments \| Natural Gas Distribution \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									555,100	542,500
Operating Segments \| Natural Gas Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									347,600	334,800
Operating Segments \| Natural Gas Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									96,900	96,000
Operating Segments \| Natural Gas Distribution \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									999,600	973,300
Operating Segments \| Natural Gas Distribution \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Natural Gas Distribution \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									55,400	57,500
Operating Segments \| Natural Gas Distribution \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									2,800	(2,200)
Operating Segments \| Natural Gas Distribution \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									6,200	(8,300)
Operating Segments \| Electric Transmission
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,306,500	1,321,500
Alternative Revenue Programs									81,800	(35,200)
Other Revenues									700	0
Operating Revenues									1,389,000	1,286,300	1,301,700
Operating Segments \| Electric Transmission \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Electric Transmission \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Electric Transmission \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Electric Transmission \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Electric Transmission \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,293,300	1,308,900
Operating Segments \| Electric Transmission \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Electric Transmission \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									13,200	12,600
Operating Segments \| Electric Transmission \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Water Distribution
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									209,000	206,000
Alternative Revenue Programs									4,600	5,400
Other Revenues									1,000	600
Operating Revenues									214,600	212,000
Operating Segments \| Water Distribution \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									132,300	130,700
Operating Segments \| Water Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									63,900	63,300
Operating Segments \| Water Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									4,500	4,400
Operating Segments \| Water Distribution \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									200,700	198,400
Operating Segments \| Water Distribution \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| Water Distribution \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									4,100	4,100
Operating Segments \| Water Distribution \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									7,000	7,200
Operating Segments \| Water Distribution \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									(2,800)	(3,700)
Operating Segments \| CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									3,626,900	3,607,900
Alternative Revenue Programs									77,500	(65,900)
Other Revenues									10,300	8,500
Operating Segments \| CL&P \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,837,100	1,828,200
Operating Segments \| CL&P \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									922,900	928,100
Operating Segments \| CL&P \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									138,300	147,700
Operating Segments \| CL&P \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									2,898,300	2,904,000
Operating Segments \| CL&P \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									587,100	620,600
Operating Segments \| CL&P \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									105,100	48,300
Operating Segments \| CL&P \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									36,400	35,000
Operating Segments \| CL&P \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									3,396,400	3,491,100
Alternative Revenue Programs									41,600	900
Other Revenues									7,000	8,300
Operating Segments \| NSTAR Electric \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,322,100	1,380,900
Operating Segments \| NSTAR Electric \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,349,400	1,391,500
Operating Segments \| NSTAR Electric \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									115,800	124,900
Operating Segments \| NSTAR Electric \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									2,787,300	2,897,300
Operating Segments \| NSTAR Electric \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									517,300	488,800
Operating Segments \| NSTAR Electric \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									73,100	76,100
Operating Segments \| NSTAR Electric \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									18,700	28,900
Operating Segments \| NSTAR Electric \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Operating Segments \| PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,200,100	1,213,000
Alternative Revenue Programs									8,600	(17,300)
Other Revenues									1,900	1,100
Operating Segments \| PSNH \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									564,500	557,500
Operating Segments \| PSNH \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									314,600	316,900
Operating Segments \| PSNH \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									77,700	79,300
Operating Segments \| PSNH \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									956,800	953,700
Operating Segments \| PSNH \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									188,900	199,500
Operating Segments \| PSNH \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									37,500	56,600
Operating Segments \| PSNH \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									15,600	15,500
Operating Segments \| PSNH \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,300	(12,300)
Other
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									1,028,500	936,300
Alternative Revenue Programs									0	0
Other Revenues									0	0
Operating Revenues									1,028,500	936,300	931,000
Other \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Other \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Other \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Other \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Other \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									61,300	47,300
Other \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Other \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									967,200	889,000
Other \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Eliminations
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									(2,070,100)	(1,997,700)
Alternative Revenue Programs									(74,200)	31,900
Other Revenues									0	0
Operating Revenues									(2,144,300)	(1,965,800)	$ (986,800)
Eliminations \| Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Eliminations \| Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									(4,300)	(4,500)
Eliminations \| Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									(11,600)	(10,000)
Eliminations \| Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									(15,900)	(14,500)
Eliminations \| Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									(1,085,200)	(1,092,200)
Eliminations \| Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Eliminations \| Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									(969,000)	(891,000)
Eliminations \| Reserve for Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers									0	0
Consolidations Eliminations \| CL&P
Disaggregation of Revenue [Line Items]
Operating Revenues									(482,100)	(454,300)
Consolidations Eliminations \| NSTAR Electric
Disaggregation of Revenue [Line Items]
Operating Revenues									(400,400)	(387,400)
Consolidations Eliminations \| PSNH
Disaggregation of Revenue [Line Items]
Operating Revenues									$ (144,700)	$ (149,200)

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) $ in Millions	12 Months Ended
SEGMENT INFORMATION - Narrative (Details) $ in Millions	Dec. 31, 2019USD ($)segment
Segment Reporting Information [Line Items]
Amount of natural gas transmission purchased \| $	$ 62.5
CL&P
Segment Reporting Information [Line Items]
Number of reportable segments	1
NSTAR Electric
Segment Reporting Information [Line Items]
Number of reportable segments	1
PSNH
Segment Reporting Information [Line Items]
Number of reportable segments	1

SEGMENT INFORMATION - Schedule

SEGMENT INFORMATION - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating Revenues	$ 2,050,400	$ 2,175,800	$ 1,884,500	$ 2,415,800	$ 2,034,900	$ 2,271,400	$ 1,853,900	$ 2,288,000	$ 8,526,470	$ 8,448,201	$ 7,751,952
Depreciation and Amortization									(1,080,700)	(1,072,000)	(863,800)
Impairment of Northern Pass Transmission			(239,600)						(239,644)	0	0
Other Operating Expenses									(5,615,700)	(5,676,300)	(5,000,000)
Operating Income	435,600	509,200	151,000	494,700	400,000	466,000	391,400	442,500	1,590,491	1,699,930	1,888,249
Interest Expense									(533,197)	(498,805)	(421,755)
Interest Income									12,800	18,100	8,300
Other Income/(Loss), Net									120,000	110,300	99,700
Income Tax (Expense)/Benefit									(273,499)	(288,972)	(578,892)
Net Income	251,900	320,800	33,300	310,600	233,200	291,300	244,600	271,400	916,572	1,040,519	995,515
Net Income Attributable to Noncontrolling Interests									(7,519)	(7,519)	(7,519)
Net Income/(Loss) Attributable to Common Shareholders	250,000	$ 318,900	$ 31,500	$ 308,700	231,300	$ 289,400	$ 242,800	$ 269,500	909,053	1,033,000	987,996
Total Assets (as of)	41,123,915				38,241,256				41,123,915	38,241,256
Cash Flows Used for Investments in Plant									2,911,489	2,569,936	2,348,105
Operating Segments \| Electric Distribution
Segment Reporting Information [Line Items]
Operating Revenues									6,976,500	6,957,200	5,542,900
Depreciation and Amortization									(651,300)	(671,800)	(542,600)
Impairment of Northern Pass Transmission									0
Other Operating Expenses									(5,525,100)	(5,548,600)	(4,072,600)
Operating Income									800,100	736,800	927,700
Interest Expense									(206,400)	(202,800)	(186,300)
Interest Income									13,300	18,700	7,300
Other Income/(Loss), Net									46,800	67,500	41,600
Income Tax (Expense)/Benefit									(135,900)	(160,200)	(288,300)
Net Income									517,900	460,000	502,000
Net Income Attributable to Noncontrolling Interests									(4,600)	(4,600)	(4,600)
Net Income/(Loss) Attributable to Common Shareholders									513,300	455,400	497,400
Total Assets (as of)	22,541,900				21,389,100				22,541,900	21,389,100
Cash Flows Used for Investments in Plant									1,104,200	961,300	1,020,700
Operating Segments \| Natural Gas Distribution
Segment Reporting Information [Line Items]
Operating Revenues									1,062,200	1,022,200	947,300
Depreciation and Amortization									(68,300)	(75,000)	(72,900)
Impairment of Northern Pass Transmission									0
Other Operating Expenses									(830,800)	(787,600)	(716,400)
Operating Income									163,100	159,600	158,000
Interest Expense									(47,400)	(44,100)	(43,100)
Interest Income									100	0	100
Other Income/(Loss), Net									1,600	7,100	3,800
Income Tax (Expense)/Benefit									(21,200)	(29,400)	(44,200)
Net Income									96,200	93,200	74,600
Net Income Attributable to Noncontrolling Interests									0	0	0
Net Income/(Loss) Attributable to Common Shareholders									96,200	93,200	74,600
Total Assets (as of)	4,345,500				3,904,900				4,345,500	3,904,900
Cash Flows Used for Investments in Plant									460,200	351,500	298,200
Operating Segments \| Electric Transmission
Segment Reporting Information [Line Items]
Operating Revenues									1,389,000	1,286,300	1,301,700
Depreciation and Amortization									(253,300)	(231,800)	(209,400)
Impairment of Northern Pass Transmission									(239,600)
Other Operating Expenses									(411,200)	(375,500)	(382,800)
Operating Income									484,900	679,000	709,500
Interest Expense									(125,700)	(120,600)	(115,100)
Interest Income									1,500	2,400	1,800
Other Income/(Loss), Net									29,200	31,100	27,300
Income Tax (Expense)/Benefit									(130,500)	(161,800)	(228,700)
Net Income									259,400	430,100	394,800
Net Income Attributable to Noncontrolling Interests									(2,900)	(2,900)	(2,900)
Net Income/(Loss) Attributable to Common Shareholders									256,500	427,200	391,900
Total Assets (as of)	10,904,000				10,285,000				10,904,000	10,285,000
Cash Flows Used for Investments in Plant									987,000	976,200	867,600
Operating Segments \| Water Distribution
Segment Reporting Information [Line Items]
Operating Revenues									214,600	212,000	15,900
Depreciation and Amortization									(46,900)	(46,500)	(3,700)
Impairment of Northern Pass Transmission									0
Other Operating Expenses									(101,000)	(99,800)	(8,300)
Operating Income									66,700	65,700	3,900
Interest Expense									(34,600)	(34,300)	(3,100)
Interest Income									0	0	100
Other Income/(Loss), Net									400	(400)	0
Income Tax (Expense)/Benefit									2,400	(100)	(2,100)
Net Income									34,900	30,900	(1,200)
Net Income Attributable to Noncontrolling Interests									0	0	0
Net Income/(Loss) Attributable to Common Shareholders									34,900	30,900	(1,200)
Total Assets (as of)	2,351,700				2,253,000				2,351,700	2,253,000
Cash Flows Used for Investments in Plant									118,000	102,300	16,000
Other
Segment Reporting Information [Line Items]
Operating Revenues									1,028,500	936,300	931,000
Depreciation and Amortization									(63,200)	(49,100)	(37,400)
Impairment of Northern Pass Transmission									0
Other Operating Expenses									(891,300)	(831,500)	(806,600)
Operating Income									74,000	55,700	87,000
Interest Expense									(170,300)	(129,300)	(90,000)
Interest Income									48,700	30,300	15,700
Other Income/(Loss), Net									1,041,500	1,185,300	1,113,000
Income Tax (Expense)/Benefit									11,700	62,500	(15,500)
Net Income									1,005,600	1,204,500	1,110,200
Net Income Attributable to Noncontrolling Interests									0	0	0
Net Income/(Loss) Attributable to Common Shareholders									1,005,600	1,204,500	1,110,200
Total Assets (as of)	20,469,600				17,874,200				20,469,600	17,874,200
Cash Flows Used for Investments in Plant									242,100	178,600	145,600
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues									(2,144,300)	(1,965,800)	(986,800)
Depreciation and Amortization									2,300	2,200	2,200
Impairment of Northern Pass Transmission									0
Other Operating Expenses									2,143,700	1,966,700	986,700
Operating Income									1,700	3,100	2,100
Interest Expense									51,200	32,300	15,800
Interest Income									(50,800)	(33,300)	(16,700)
Other Income/(Loss), Net									(999,500)	(1,180,300)	(1,086,000)
Income Tax (Expense)/Benefit									0	0	(100)
Net Income									(997,400)	(1,178,200)	(1,084,900)
Net Income Attributable to Noncontrolling Interests									0	0	0
Net Income/(Loss) Attributable to Common Shareholders									(997,400)	(1,178,200)	(1,084,900)
Total Assets (as of)	$ (19,488,800)				$ (17,464,900)				(19,488,800)	(17,464,900)
Cash Flows Used for Investments in Plant									$ 0	$ 0	$ 0

ACQUISITION OF AQUARION AND G_3

ACQUISITION OF AQUARION AND GOODWILL - Narrative (Details) - USD ($)	Oct. 01, 2019	Dec. 04, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Acquisition of Aquarion			$ 0	$ 0	$ 877,652,000
Operating Revenues					15,900,000
Pre-tax income					1,100,000
Impairment loss	$ 0
Aquarion Water Company
Business Acquisition [Line Items]
Consideration transferred		$ 1,675,000,000
Acquisition of Aquarion		880,000,000
Consideration transferred, liabilities incurred		795,000,000
Equity interest		745,000,000
Aquarion shareholder loan paid at closing		$ 135,000,000
Operating Revenues					$ 7,947,700,000

ACQUISITION OF AQUARION AND G_4

ACQUISITION OF AQUARION AND GOODWILL - Schedule of Pro Forma Information (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / shares
Business Acquisition [Line Items]
Operating Revenues	$ 15.9
Aquarion Water Company
Business Acquisition [Line Items]
Operating Revenues	7,947.7
Net Income Attributable to Common Shareholders	$ 1,019.1
Basic EPS (in dollars per share) \| $ / shares	$ 3.21
Diluted EPS (in dollars per share) \| $ / shares	$ 3.20

ACQUISITION OF AQUARION AND G_5

ACQUISITION OF AQUARION AND GOODWILL - Schedule of Goodwill by Reportable Segments (Details) $ in Billions	12 Months Ended
	Dec. 31, 2019USD ($)
Business Acquisition [Line Items]
Goodwill	$ 4.4
Electric Distribution
Business Acquisition [Line Items]
Goodwill	2.5
Electric Transmission
Business Acquisition [Line Items]
Goodwill	0.6
Natural Gas Distribution
Business Acquisition [Line Items]
Goodwill	0.4
Water Distribution
Business Acquisition [Line Items]
Goodwill	$ 0.9

QUARTERLY FINANCIAL DATA (UNA_3

QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data [Line Items]
Operating Revenues	$ 2,050,400	$ 2,175,800	$ 1,884,500	$ 2,415,800	$ 2,034,900	$ 2,271,400	$ 1,853,900	$ 2,288,000	$ 8,526,470	$ 8,448,201	$ 7,751,952
Operating Income	435,600	509,200	151,000	494,700	400,000	466,000	391,400	442,500	1,590,491	1,699,930	1,888,249
Net Income	251,900	320,800	33,300	310,600	233,200	291,300	244,600	271,400	916,572	1,040,519	995,515
Net Income Attributable to Common Shareholders	$ 250,000	$ 318,900	$ 31,500	$ 308,700	$ 231,300	$ 289,400	$ 242,800	$ 269,500	$ 909,053	$ 1,033,000	$ 987,996
Basic EPS (in dollars per share)	$ 0.77	$ 0.98	$ 0.10	$ 0.97	$ 0.73	$ 0.91	$ 0.76	$ 0.85	$ 2.83	$ 3.25	$ 3.11
Diluted EPS (in dollars per share)	$ 0.76	$ 0.98	$ 0.10	$ 0.97	$ 0.73	$ 0.91	$ 0.76	$ 0.85	$ 2.81	$ 3.25	$ 3.11
Impairment of Northern Pass Transmission			$ 239,600						$ 239,644	$ 0	$ 0
CL&P
Quarterly Financial Data [Line Items]
Operating Revenues	$ 788,700	$ 853,900	740,800	$ 849,200	$ 751,300	$ 865,000	$ 694,900	$ 785,000	3,232,551	3,096,174	2,887,359
Operating Income	152,700	190,300	166,800	171,800	142,800	172,700	163,100	157,200	681,649	635,837	683,354
Net Income	83,900	111,700	104,800	110,500	79,100	100,300	99,700	98,600	410,852	377,717	376,726
NSTAR Electric
Quarterly Financial Data [Line Items]
Operating Revenues	686,400	878,700	681,900	797,600	712,600	939,500	690,700	770,100	3,044,642	3,112,926	2,980,629
Operating Income	135,500	219,400	134,200	137,800	126,000	205,500	133,600	119,000	626,890	584,123	688,440
Net Income	93,400	154,900	89,700	94,000	77,500	140,600	87,900	77,100	431,956	383,090	374,726
PSNH
Quarterly Financial Data [Line Items]
Operating Revenues	268,200	280,400	240,900	276,400	254,900	290,200	235,100	267,400	1,065,936	1,047,619	981,624
Operating Income	56,000	64,500	46,300	49,700	37,200	56,500	46,900	55,800	216,467	196,414	265,873
Net Income	$ 33,400	$ 40,900	$ 26,900	$ 32,800	$ 14,300	$ 40,700	$ 25,800	$ 35,100	$ 134,048	$ 115,876	$ 135,996

SCHEDULE I - FINANCIAL INFORM_2

SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - BALANCE SHEET (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash	$ 15,432	$ 108,068
Prepayments and Other Current Assets	342,135	260,995
Total Current Assets	2,414,539	2,292,224
Deferred Debits and Other Assets:
Investments in Subsidiary Companies, at Equity	871,633	464,286
Goodwill	4,427,266	4,427,266
Other Long-Term Assets	512,238	398,407
Total Deferred Debits and Other Assets	11,123,906	10,338,604
Total Assets	41,123,915	38,241,256
Current Liabilities:
Notes Payable	889,084	910,000
Long-Term Debt – Current Portion	327,411	837,319
Other Current Liabilities	836,834	823,006
Total Current Liabilities	3,605,563	4,112,882
Total Deferred Credits and Other Liabilities	10,421,838	9,653,913
Capitalization:
Long-Term Debt	13,770,828	12,248,743
Common Shareholders' Equity:
Common Shares	1,729,292	1,669,392
Capital Surplus, Paid in	7,087,768	6,241,222
Retained Earnings	4,177,048	3,953,974
Accumulated Other Comprehensive Loss	(65,059)	(60,000)
Treasury Stock	(299,055)	(317,771)
Common Shareholders' Equity	12,629,994	11,486,817	$ 11,086,242	$ 10,711,734
Total Liabilities and Capitalization	41,123,915	38,241,256
Eversource
Current Assets:
Cash	1,469	591	$ 521	$ 93
Accounts Receivable from Subsidiaries	25,070	32,175
Notes Receivable from Subsidiaries	1,376,000	991,400
Prepayments and Other Current Assets	33,546	26,861
Total Current Assets	1,436,085	1,051,027
Deferred Debits and Other Assets:
Investments in Subsidiary Companies, at Equity	13,162,337	12,009,659
Notes Receivable from Subsidiaries	157,000	323,500
Accumulated Deferred Income Taxes	27,578	40,454
Goodwill	3,231,811	3,231,811
Other Long-Term Assets	92,394	73,669
Total Deferred Debits and Other Assets	16,671,120	15,679,093
Total Assets	18,107,205	16,730,120
Current Liabilities:
Notes Payable	878,584	631,500
Long-Term Debt – Current Portion	23,933	378,883
Accounts Payable to Subsidiaries	4,333	8,432
Other Current Liabilities	62,385	57,877
Total Current Liabilities	969,235	1,076,692
Total Deferred Credits and Other Liabilities	149,637	134,614
Capitalization:
Long-Term Debt	4,358,339	4,031,997
Common Shareholders' Equity:
Common Shares	1,729,292	1,669,392
Capital Surplus, Paid in	7,087,768	6,241,222
Retained Earnings	4,177,048	3,953,974
Accumulated Other Comprehensive Loss	(65,059)	(60,000)
Treasury Stock	(299,055)	(317,771)
Common Shareholders' Equity	12,629,994	11,486,817
Total Liabilities and Capitalization	$ 18,107,205	$ 16,730,120

SCHEDULE I - FINANCIAL INFORM_3

SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENTS OF INCOME (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Income Statements, Captions [Line Items]
Operating Revenues	$ 2,050,400	$ 2,175,800	$ 1,884,500	$ 2,415,800	$ 2,034,900	$ 2,271,400	$ 1,853,900	$ 2,288,000	$ 8,526,470	$ 8,448,201	$ 7,751,952
Operating Expenses:
Other									1,363,113	1,335,213	1,307,052
Operating Income	435,600	509,200	151,000	494,700	400,000	466,000	391,400	442,500	1,590,491	1,699,930	1,888,249
Interest Expense									533,197	498,805	421,755
Other Income, Net:
Equity in Earnings of Subsidiaries									42,200	3,800	27,400
Other Income, Net									132,777	128,366	107,913
Income Before Income Tax Expense									1,190,071	1,329,491	1,574,407
Income Tax Benefit									273,499	288,972	578,892
Net Income	$ 251,900	$ 320,800	$ 33,300	$ 310,600	$ 233,200	$ 291,300	$ 244,600	$ 271,400	$ 916,572	$ 1,040,519	$ 995,515
Basic Earnings Per Common Share (in dollars per share)	$ 0.77	$ 0.98	$ 0.10	$ 0.97	$ 0.73	$ 0.91	$ 0.76	$ 0.85	$ 2.83	$ 3.25	$ 3.11
Diluted Earnings Per Common Share (in dollars per share)	$ 0.76	$ 0.98	$ 0.10	$ 0.97	$ 0.73	$ 0.91	$ 0.76	$ 0.85	$ 2.81	$ 3.25	$ 3.11
Weighted Average Common Shares Outstanding:
Basic (in shares)									321,416,086	317,370,369	317,411,097
Diluted (in shares)									322,941,636	317,993,934	318,031,580
Eversource
Condensed Income Statements, Captions [Line Items]
Operating Revenues									$ 0	$ 0	$ 0
Operating Expenses:
Other									50,100	(6,552)	(32,189)
Operating Income									(50,100)	6,552	32,189
Interest Expense									163,937	123,638	80,700
Other Income, Net:
Equity in Earnings of Subsidiaries									1,001,526	1,049,748	993,063
Other, Net									68,137	47,581	23,339
Other Income, Net									1,069,663	1,097,329	1,016,402
Income Before Income Tax Expense									855,626	980,243	967,891
Income Tax Benefit									(53,427)	(52,757)	(20,105)
Net Income									$ 909,053	$ 1,033,000	$ 987,996
Basic Earnings Per Common Share (in dollars per share)									$ 2.83	$ 3.25	$ 3.11
Diluted Earnings Per Common Share (in dollars per share)									$ 2.81	$ 3.25	$ 3.11
Weighted Average Common Shares Outstanding:
Basic (in shares)									321,416,086	317,370,369	317,411,097
Diluted (in shares)									322,941,636	317,993,934	318,031,580

SCHEDULE I - FINANCIAL INFORM_4

SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENTS OF COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Statement of Income Captions [Line Items]
Net Income	$ 251,900	$ 320,800	$ 33,300	$ 310,600	$ 233,200	$ 291,300	$ 244,600	$ 271,400	$ 916,572	$ 1,040,519	$ 995,515
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments									1,393	1,756	1,974
Changes in Unrealized Gains/(Losses) on Marketable Securities									1,166	(547)	(350)
Change in Funded Status of Pension, SERP and PBOP Benefit Plans									(7,618)	5,194	(2,745)
Other Comprehensive (Loss)/Income, Net of Tax									(5,059)	6,403	(1,121)
Comprehensive Income Attributable to Common Shareholders									903,994	1,039,403	986,875
Eversource
Condensed Statement of Income Captions [Line Items]
Net Income									909,053	1,033,000	987,996
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments									1,393	1,756	1,974
Changes in Unrealized Gains/(Losses) on Marketable Securities									1,166	(547)	(350)
Change in Funded Status of Pension, SERP and PBOP Benefit Plans									(7,618)	5,194	(2,745)
Other Comprehensive (Loss)/Income, Net of Tax									(5,059)	6,403	(1,121)
Comprehensive Income Attributable to Common Shareholders									$ 903,994	$ 1,039,403	$ 986,875

SCHEDULE I - FINANCIAL INFORM_5

SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENT OF CASH FLOW (Details) - USD ($) $ in Thousands	Dec. 30, 2019	Jun. 04, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Net Income			$ 251,900	$ 320,800	$ 33,300	$ 310,600	$ 233,200	$ 291,300	$ 244,600	$ 271,400	$ 916,572	$ 1,040,519	$ 995,515
Flows Provided by Operating Activities:
Equity in Earnings of Subsidiaries											(42,200)	(3,800)	(27,400)
Deferred Income Taxes											209,812	174,812	491,630
Other											(196,087)	(111,225)	(204,421)
Accounts Receivables from Subsidiaries											(98,716)	(141,433)	(117,155)
Taxes Receivable/Accrued, Net											(16,129)	(67,770)	52,284
Other Current Assets and Liabilities, Net											(11,603)	78,226	91,545
Net Cash Flows Provided by Operating Activities											2,009,577	1,830,543	1,996,202
Investing Activities:
Other Investing Activities											24,204	6,754	5,479
Net Cash Flows Used in Investing Activities											(3,274,288)	(2,437,046)	(3,230,516)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	$ 425,400	$ 426,900									852,254	0	0
Cash Dividends on Common Shares											(663,239)	(640,110)	(602,083)
Issuance of Long-Term Debt											1,520,000	2,200,000	2,500,000
Retirement of Long-Term Debt											(801,078)	(1,050,330)	(745,000)
Increase/(Decrease) in Notes Payable											325,370	(379,310)	72,810
Other Financing Activities											(1,006)	(28,457)	(4,754)
Net Cash Flows Provided by/(Used in) Financing Activities											1,172,450	729,937	1,213,454
Cash, Cash Equivalents and Restricted Cash - Beginning of Year						108,068					108,068
Cash, Cash Equivalents and Restricted Cash - End of Year			15,432				108,068				15,432	108,068
Cash Paid/(Received) During the Year for:
Interest											532,400	503,200	419,100
Income Taxes											56,000	158,800	30,800
Eversource
Operating Activities:
Net Income											909,053	1,033,000	987,996
Flows Provided by Operating Activities:
Equity in Earnings of Subsidiaries											(1,001,526)	(1,049,748)	(993,063)
Cash Dividends Received from Subsidiaries											883,000	569,500	753,300
Deferred Income Taxes											13,382	20,032	37,867
Other											19,584	(31,093)	(36,052)
Accounts Receivables from Subsidiaries											7,105	(28,716)	29,405
Taxes Receivable/Accrued, Net											(605)	(20,207)	1,555
Accounts Payable to Subsidiaries											(4,099)	(9,817)	9,763
Other Current Assets and Liabilities, Net											(2,503)	2,553	7,536
Net Cash Flows Provided by Operating Activities											823,391	485,504	798,307
Investing Activities:
Capital Contributions to Subsidiaries											(1,039,000)	(955,700)	(1,156,731)
Return of Capital from Subsidiary											0	530,000	0
Increase in Notes Receivable from Subsidiaries											(218,100)	(158,210)	(192,100)
Other Investing Activities											(1,799)	(1,149)	1,484
Net Cash Flows Used in Investing Activities											(1,258,899)	(585,059)	(1,347,347)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs											852,254	0	0
Cash Dividends on Common Shares											(663,239)	(640,110)	(602,083)
Issuance of Long-Term Debt											0	1,550,000	1,200,000
Retirement of Long-Term Debt											(350,000)	(450,000)	0
Increase/(Decrease) in Notes Payable											593,370	(347,810)	(42,690)
Other Financing Activities											4,001	(12,455)	(5,759)
Net Cash Flows Provided by/(Used in) Financing Activities											436,386	99,625	549,468
Net Increase/(Decrease) in Cash and Cash Equivalents											878	70	428
Cash, Cash Equivalents and Restricted Cash - Beginning of Year						$ 591				$ 521	591	521	93
Cash, Cash Equivalents and Restricted Cash - End of Year			$ 1,469				$ 591				1,469	591	521
Cash Paid/(Received) During the Year for:
Interest											161,323	118,533	73,868
Income Taxes											$ (63,227)	$ (30,239)	$ (59,526)

SCHEDULE II - VALUATION AND Q_2

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CL&P
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Period of accounts receivable recoverable under financial or medical duress		180 days
Yankee Gas Services Company
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Period of accounts receivable recoverable under financial or medical duress		90 days
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		$ 212,723	$ 195,708	$ 200,630
Additions, Charged to Costs and Expense		63,446	61,337	44,665
Additions, Charged to Other Accounts	[1]	57,223	48,671	47,630
Deductions	[2]	108,571	92,993	97,217
Balance at end of period		224,821	212,723	195,708
Allowance for Doubtful Accounts \| CL&P
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		88,034	78,872	86,391
Additions, Charged to Costs and Expense		15,947	15,831	5,312
Additions, Charged to Other Accounts	[1]	38,935	29,524	25,533
Deductions	[2]	45,568	36,193	38,364
Balance at end of period		97,348	88,034	78,872
Allowance for Doubtful Accounts \| NSTAR Electric
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		74,516	69,666	70,284
Additions, Charged to Costs and Expense		25,079	22,279	21,252
Additions, Charged to Other Accounts	[1]	12,556	14,971	14,273
Deductions	[2]	36,745	32,400	36,143
Balance at end of period		75,406	74,516	69,666
Allowance for Doubtful Accounts \| PSNH
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		11,065	10,481	9,941
Additions, Charged to Costs and Expense		6,726	6,383	6,917
Additions, Charged to Other Accounts	[1]	872	953	464
Deductions	[2]	8,166	6,752	6,841
Balance at end of period		$ 10,497	$ 11,065	$ 10,481

[1]	Amounts relate to uncollectible accounts receivables reserved for that are not charged to bad debt expense. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows NSTAR Electric and NSTAR Gas to recover in rates, amounts associated with certain uncollectible hardship accounts receivable.
[2]	Amounts written off, net of recoveries.