National Grid (NGG) FWPFree writing prospectus

Filed Pursuant to Rule 433

Registration Statement No. 333-256888

Dated: June 7, 2023

Pricing Term Sheet

National Grid plc

U.S.$700,000,000 5.602% Notes due 2028

Pricing Term Sheet

*) A securities rating is not a recommendation to buy, sell or hold securities and may be revised or withdrawn at any time.

**) The issuer expects that delivery of the Notes will be made to investors on or about June 12, 2023 (such settlement being referred to as “T+3”). Under Rule 15c6-1 under the Exchange Act, trades in the secondary market are required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade Notes prior to two business days before the delivery of the Notes hereunder may be required, by virtue of the fact that the Notes initially settle in T+3, to specify an alternate settlement arrangement at the time of any such trade to prevent a failed settlement. Purchasers of the Notes who wish to trade the Notes prior to their date of delivery hereunder should consult their advisors.

Capitalized terms used but not defined in this term sheet have the meanings set forth in the base prospectus as supplemented by the preliminary prospectus supplement.

The issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, you may obtain a copy of the base prospectus and the preliminary prospectus supplement from BofA Securities, Inc. by calling toll free 1-800-294-1322, Goldman Sachs & Co. LLC at 1-866-471-2526, Mizuho Securities USA LLC at 1-866-271-7403 or Wells Fargo Securities, LLC at 1-800-645-3751.

National Grid plc

U.S.$800,000,000 5.809% Notes due 2033

Pricing Term Sheet

*) A securities rating is not a recommendation to buy, sell or hold securities and may be revised or withdrawn at any time.

**) The issuer expects that delivery of the Notes will be made to investors on or about June 12, 2023 (such settlement being referred to as “T+3”). Under Rule 15c6-1 under the Exchange Act, trades in the secondary market are required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade Notes prior to two business days before the delivery of the Notes hereunder may be required, by virtue of the fact that the Notes initially settle in T+3, to specify an alternate settlement arrangement at the time of any such trade to prevent a failed settlement. Purchasers of the Notes who wish to trade the Notes prior to their date of delivery hereunder should consult their advisors.

Capitalized terms used but not defined in this term sheet have the meanings set forth in the base prospectus as supplemented by the preliminary prospectus supplement.

The issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, you may obtain a copy of the base prospectus and the preliminary prospectus supplement from BofA Securities, Inc. by calling toll free 1-800-294-1322, Goldman Sachs & Co. LLC at 1-866-471-2526, Mizuho Securities USA LLC at 1-866-271-7403 or Wells Fargo Securities, LLC at 1-800-645-3751.