FuelCell Energy (FCEL) 424B5Prospectus supplement for primary offering

We have not designated any amount of the net proceeds, if any, we will receive from the exercise of the Registered Warrants for any particular purpose. Accordingly, our management will have broad discretion as to the application of such net proceeds and could use them for purposes other than those contemplated at the time of this offering. Our stockholders may not agree with the manner in which our management chooses to allocate and spend such net proceeds. In addition, such proceeds could be applied in ways that do not improve our operating results or increase the value of your investment. Our failure to apply these funds effectively could have a material adverse effect on our business, delay the development of our products and cause the price of our common stock to decline.

In order to raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the exercise price of the Registered Warrants. We may sell shares of our common stock or other securities convertible or exchangeable into our common stock in any other offering at a price per share that is less than the exercise price of the Registered Warrants, and investors purchasing shares of our common stock or other securities in the future could have rights superior to existing stockholders. The exercise of our outstanding options and warrants, including the Registered Warrants, may adversely affect our stock price due to sales of a large number of shares of our common stock or the perception that such sales could occur. These factors also could make it more difficult to raise funds through future offerings of our securities, and could adversely impact the terms under which we could obtain additional equity capital. Exercise of outstanding options and warrants or any future issuance of additional shares of our common stock or other equity securities, including but not limited to options, warrants, restricted stock units or other derivative

The validity of the shares of common stock being offered hereby will be passed upon for us by Foley & Lardner LLP, Boston, Massachusetts.

The consolidated financial statements of FuelCell Energy, Inc. as of October 31, 2020 and 2019, and for each of the years in the three-year period ended October 31, 2020, have been incorporated by reference herein and in the registration statement in reliance upon the report of KPMG LLP, independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

The audit report covering the October 31, 2020 financial statements refers to changes in the Company’s methods of accounting for leases and revenue due to the adoption of new accounting guidance.

This prospectus supplement and the accompanying prospectus are part of a registration statement that we have filed with the SEC relating to the securities to be offered. This prospectus supplement and the accompanying prospectus do not contain all of the information we have included in the registration statement and the accompanying exhibits and schedules in accordance with the rules and regulations of the SEC, and we refer you to the omitted information. The statements this prospectus supplement makes pertaining to the content of any contract, agreement or other document that is an exhibit to the registration statement necessarily are summaries of their material provisions and do not describe all provisions, exceptions and qualifications contained in those contracts, agreements or documents. You should read those contracts, agreements and documents for information that may be important to you. The registration statement, exhibits and schedules are available on the SEC’s Internet web site.

The SEC allows us to incorporate by reference much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus supplement is considered to be part of this prospectus supplement. Because we are incorporating by reference future filings with the SEC, this prospectus supplement is continually updated and those future filings may modify or supersede some of the information included or incorporated in this prospectus supplement. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus supplement or in any document previously incorporated by reference have been modified or superseded. This prospectus supplement incorporates by reference the documents listed below and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (in each case, other than those documents or the portions of those documents not deemed to be filed) prior to the termination of the offering:

This prospectus is part of a registration statement that FuelCell Energy, Inc. (“FuelCell Energy,” the “Company,” “we,” “our,” “us” or similar terms) filed with the Securities and Exchange Commission (the “SEC”) using a “shelf” registration process. Under this shelf registration process, we may from time to time sell shares of our common stock in one or more offerings. Each time we sell securities, we will, to the extent required by law, provide a prospectus supplement that will contain specific information about the terms of the offering. We may also add, update or change in any accompanying prospectus supplement any of the information contained in this prospectus. To the extent there is a conflict between the information contained in this prospectus and the prospectus supplement, you should rely on the information in the prospectus supplement, provided that if any statement in one of these documents is inconsistent with a statement in another document having a later date — for example, a document incorporated by reference in this prospectus or any prospectus supplement — the statement in the document having the later date modifies or supersedes the earlier statement. This prospectus, together with any accompanying prospectus supplement and any other document we may authorize to be delivered to you, includes all material information relating to the offering of our common stock.

As permitted by the rules and regulations of the SEC, the registration statement, of which this prospectus forms a part, includes additional information not contained in this prospectus. You may read the registration statement and the other reports we file with the SEC at the SEC’s web site or at the SEC’s offices as described below under the heading “Where You Can Find Additional Information.”

This prospectus, any prospectus supplement, the documents incorporated by reference herein and therein and any related free writing prospectuses issued by us may contain forward-looking statements (within the meaning of the Private Securities Litigation Reform Act of 1995 (the “PSLRA”)) about our financial condition, results of operations, plans, objectives, expectations, future performance and business. Statements preceded by, followed by or that include words such as “expects,” “anticipates,” “estimates,” “goals,” “projects,” “intends,” “plans,” “believes,” “predicts,” “should,” “seeks,” “will,” “could,” “would,” “may,” “forecast,” or words or phrases of similar import are intended to identify some of the forward-looking statements and are included, along with this statement, for purposes of complying with the safe harbor provisions of the PSLRA. Forward-looking statements are neither historical facts, nor assurances of future performance. Instead, such statements are based only on our beliefs, expectations and assumptions regarding the future. As such, the realization of matters expressed in forward-looking statements involves inherent risks and uncertainties. Our actual results and future events may differ materially from those set forth in or contemplated by the forward-looking statements due to, among other factors, the risks and uncertainties described in or incorporated by reference into this prospectus, including under the heading “Risk Factors,” as well as any risks or uncertainties described in or incorporated by reference into any prospectus supplement. Any forward-looking statement contained in this prospectus, any prospectus supplement, the documents incorporated by reference herein and therein, and any related free writing prospectuses issued by us speaks only as of the date on which the statement was made, and we undertake no obligation to update publicly or revise any forward-looking statements for any reason, whether as a result of new information, future events or otherwise. New risks emerge from time to time, and we cannot predict all of the risks that may impact our business or the extent to which any particular risk, or combination of risks, may cause actual results to differ materially from those contained in any forward-looking statement.

Market data and industry forecasts and projections used in this prospectus and documents incorporated by reference herein have been obtained from independent industry sources. Forecasts, projections and other forward-looking information obtained from such sources are subject to similar qualifications and uncertainties as other forward-looking statements in this prospectus and documents incorporated by reference herein.

The SEC allows us to “incorporate by reference” the information that we file with it, which means that we can disclose important information to you by referring you to other documents. The information

In this prospectus, unless otherwise stated or the context otherwise requires, references to “FuelCell Energy,” the “Company,” “we,” “us” and “our” and similar references refer to FuelCell Energy, Inc. and our consolidated subsidiaries.

An investment in our common stock involves a high degree of risk. You should carefully consider the risk factors incorporated herein by reference to our most recent Annual Report on Form 10-K and the other information contained in this prospectus, as updated by our Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and subsequent filings under the Exchange Act and the risk factors and other information contained in the applicable prospectus supplement before acquiring any of our securities.

Unless otherwise provided in the applicable prospectus supplement, we currently intend to use the net proceeds from our sale of common stock under this prospectus for general corporate purposes, which may include future investments in businesses, products, services and/or technologies, including strategic growth opportunities, the repayment, redemption or refinancing of indebtedness, research with respect to and the development of our products, working capital, capital expenditures, and acquisitions and repurchases of our securities. We may set forth additional information on the use of proceeds from the sale of the common stock we offer under this prospectus in a prospectus supplement relating to the specific offering. We have not determined the amount of net proceeds to be used specifically for the foregoing purposes. As a result, our management will have broad discretion in the allocation of the net proceeds.

The following description of our capital stock is a summary and does not purport to be complete. It is subject to, and qualified in its entirety by reference to, our Certificate of Incorporation, as amended (the “Certificate of Incorporation”), and our Amended and Restated By-laws (the “By-laws”), each of which is incorporated by reference as an exhibit to the registration statement of which this prospectus is a part. We encourage you to read our Certificate of Incorporation, our By-laws and the applicable provisions of the Delaware General Corporation Law (“DGCL”) for additional information.

Under our Certificate of Incorporation, we are authorized to issue 337,500,000 shares of common stock, par value $0.0001 per share, and 250,000 shares of preferred stock, par value $0.01 per share, in one or more series designated by our board of directors, of which 105,875 shares of our preferred stock have been designated as 5% Series B Cumulative Convertible Perpetual Preferred Stock (“Series B Preferred Stock”). Pursuant to our Certificate of Incorporation, our undesignated shares of preferred stock include all of our shares of preferred stock that were previously designated as Series C Convertible Preferred Stock and Series D Convertible Preferred Stock, as all such shares have been retired and therefore have the status of authorized and unissued shares of preferred stock undesignated as to series.

As of November 27, 2020, 294,706,758 shares of our common stock were issued and outstanding and 64,020 shares of our Series B Preferred Stock were issued and outstanding. No other shares of our preferred stock were issued and outstanding.

As of November 27, 2020, we were obligated, if and when the holders exercise their conversion rights, to issue approximately 37,837 shares of our common stock upon conversion of all of the issued and outstanding Series B Preferred Stock.

As of November 27, 2020, there were outstanding options to purchase 23,891 shares of our common stock under our equity incentive plans, 1,195,398 shares of our common stock were reserved for issuance upon time-based vesting of outstanding restricted stock units (“RSUs”) granted under our equity incentive plans, 2,938,564 shares of our common stock were reserved for potential issuance in connection with the settlement of performance-based RSUs under our equity incentive plans, and 30,248 shares of our common stock were reserved for future issuance under our employee stock purchase plan.

As of November 27, 2020, there were outstanding warrants to purchase up to 2,700,000 shares of our common stock held by Orion Energy Credit Opportunities Fund II, L.P., Orion Energy Credit Opportunities Fund II GPFA, L.P., Orion Energy Credit Opportunities Fund II PV, L.P., and Orion Energy Credit Opportunities FuelCell Co-Invest, L.P. These warrants were issued pursuant to our senior secured credit facility with Orion Energy Partners Investment Agent, LLC, as administrative agent and collateral agent, and these affiliated lenders. The exercise price of these warrants is $0.242 per share, and the expiration date of such warrants is November 22, 2028.

No dividends or other distributions may be paid or set apart for payment on our common stock (other than a dividend payable solely in shares of a like or junior ranking), nor may any stock junior to or on parity with the Series B Preferred Stock be redeemed, purchased or otherwise acquired for any consideration (or any money paid to or made available for a sinking fund for such stock) by us or on our behalf  (except by conversion into or exchange for shares of a like or junior ranking), unless all accumulated and unpaid dividends on the Series B Preferred Stock have been paid or funds or shares of common stock have been set aside for payment of such accumulated and unpaid dividends.

The dividend on the Series B Preferred Stock may be paid in cash or, at the option of the holder, in shares of our common stock, which will be registered pursuant to a registration statement to allow for the immediate sale of these shares of common stock into the public market.

We may, at our option, cause shares of Series B Preferred Stock to be automatically converted into that number of shares of our common stock that are issuable at the then-prevailing conversion rate. We may exercise our conversion right only if the closing price of our common stock exceeds 150% of the then-prevailing conversion price ($1,692.00 per share as of July 31, 2020 and October 31, 2020) for 20 trading days during any consecutive 30 trading day period, as described in the Series B Certificate of Designation.

If the holders of Series B Preferred Stock elect to convert their shares in connection with certain “fundamental changes” ​(as defined in the Series B Certificate of Designation and described below), we will in certain circumstances increase the conversion rate by a number of additional shares of common stock upon conversion or, in lieu thereof, we may in certain circumstances elect to adjust the conversion rate and related conversion obligation so that shares of Series B Preferred Stock are converted into shares of the acquiring or surviving company, in each case as described in the Series B Certificate of Designation.

The adjustment of the conversion price is to prevent dilution of the interests of the holders of the Series B Preferred Stock from certain dilutive transactions with holders of our common stock.

Notwithstanding the foregoing, holders of shares of the Series B Preferred Stock will not have the right to require us to redeem their shares if:

Moreover, we will not be required to redeem any Series B Preferred Stock upon the occurrence of a fundamental change if a third party makes an offer to purchase the Series B Preferred Stock in the manner, at the price, at the times and otherwise in compliance with the requirements set forth above and such third party purchases all shares of Series B Preferred Stock validly tendered and not withdrawn.

We may, at our option, elect to pay the redemption price in cash, in shares of our common stock valued at a discount of 5% from the market price of shares of our common stock, or in any combination thereof. Notwithstanding the foregoing, we may only pay such redemption price in shares of our common stock that are registered under the Securities Act of 1933, as amended (the “Securities Act”), and which are eligible for immediate sale in the public market by non-affiliates of our Company.