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Exhibit 4.1

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THE OFFER AND SALE OF THIS SECURITY AND THE SHARES OF COMMON STOCK ISSUABLE UPON EXERCISE OF THIS SECURITY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND THIS SECURITY AND SUCH SHARES MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED EXCEPT (A) PURSUANT TO A REGISTRATION STATEMENT THAT IS EFFECTIVE UNDER THE SECURITIES ACT; OR (B) PURSUANT TO AN EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT.

TRANSFERS, PLEDGES OR OTHER DISPOSITIONS HEREOF, OR OF ANY BENEFICIAL INTEREST HEREIN, ARE SUBJECT TO RESTRICTIONS SET FORTH IN THE WARRANT AGREEMENT REFERRED TO HEREIN. ANY PURPORTED TRANSFER, PLEDGE OR OTHER DISPOSITION IN VIOLATION OF SUCH RESTRICTIONS WILL BE VOID AND OF NO FORCE OR EFFECT.

WARRANT AGREEMENT

WARRANT AGREEMENT, dated as of June 22, 2026 (the “Effective Date”), between FuelCell Energy, Inc., a Delaware corporation, as issuer (the “Company”), and FIT Energy USA LP (“FIT”), as the initial Holder (as defined in this Warrant Agreement).

In consideration of the mutual agreements herein contained, each party to this Warrant Agreement (as defined below) agrees as follows.

 As used herein, the terms set forth below shall have the following meanings:

 “Affiliate” with respect to any person means any other person directly or indirectly controlling or controlled by or under direct or indirect common control with such specified person. For the purposes of this definition, “control” when used with respect to any person, means the power to direct the management and policies of such person, directly or indirectly, whether through the ownership of voting securities, by contract or otherwise and the terms “controlling” and “controlled” have meanings correlative to the foregoing.

“Aggregate Strike Price” means, with respect to the Exercise of any Warrant, an amount equal to the product of (a) the number of Underlying Shares of such Warrant that are being so Exercised; and (b) the Strike Price on the Exercise Date for such Exercise.

“Authorized Denomination” means, with respect to a Warrant, either (a) such Warrant in its entirety, representing all of the Underlying Shares thereof; or (b) any portion of such Warrant that represents a whole number of the Underlying Shares thereof.

“Block Systems” means power generation platforms manufactured by the Company.

“Business Day” means any day other than a Saturday, a Sunday or any day on which the Federal Reserve Bank of New York is authorized or required by law or executive order to close or be closed.

“Certificate” means any Electronic Certificate or Physical Certificate.

“Close of Business” means 5:00 p.m., New York City time.

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“Commercial Agreement” means that certain Capital Equipment Purchase Agreement, dated as of the date hereof, between the Company and FIT.

“Common Stock” means the common stock, $0.0001 par value per share, of the Company, subject to Section 13.

“Company” means FuelCell Energy, Inc., a Delaware corporation.

“Effective Date” means the date first set forth above.

“Electronic Certificate” means any electronic book entry maintained by the Company in the Register that represents one (1) or more Warrants.

“Exchange Act” means the U.S. Securities Exchange Act of 1934, as amended.

“Exercise” means a Mandatory Exercise or an Optional Exercise. The terms “Exercised” and “Exercisable” will have a meaning correlative to the foregoing.

“Exercise Date” means, with respect to an Optional Exercise, the first Business Day on which the requirements set forth in Section 5(a) for such Optional Exercise are satisfied, and with respect to a Mandatory Exercise, an Exercise Date designated with respect to any Warrant pursuant to Section 6.

“Exercise Period” means (a) with respect to any First Tranche Warrant, the First Tranche Exercise Period; (b) with respect to any Second Tranche Warrant, the Second Tranche Exercise Period; and (c) with respect to any Third Tranche Warrant, the Third Tranche Exercise Period.

“Exercise Period Expiration Date” means (a) with respect to any First Tranche Warrant, the date that is twenty-four (24) months following the First Tranche Vesting Date; (b) with respect to any Second Tranche Warrant, the date that is twenty-four (24) months following the Second Tranche Vesting Date; and (c) with respect to any Third Tranche Warrant, the date that is twenty-four (24) months following the Third Tranche Vesting Date; provided, however, that if any such date is not a Business Day, the Exercise Period Expiration Date shall be the immediately following Business Day.

“First Tranche Deposit” means the payment by the Holder (or its Affiliates) of a non-refundable deposit equal to sixteen percent (16%) of the order value for the initial 100 MW of Block Systems pursuant to the Commercial Agreement.

“First Tranche Exercise Period” means the period from, and including, the First Tranche Vesting Date to, and including, the Exercise Period Expiration Date applicable to the First Tranche Warrants.

“First Tranche Vesting Date” means the date on which the First Tranche Vesting Event occurs.

“First Tranche Vesting Event” means the Company’s receipt of the First Tranche Deposit.

“First Tranche Warrants” has the meaning set forth in Section 3(a).

 “Fundamental Transaction” shall have the meaning specified in Section 13(a).

“Holder” means a person in whose name any Warrant is registered on the Register.

“Initial Issue Date” means the Effective Date.

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“Last Reported Sale Price” of the Common Stock for any Trading Day means the closing sale price per share (or, if no closing sale price is reported, the average of the last bid price and the last ask price per share or, if more than one in either case, the average of the average last bid prices and the average last ask prices per share) of the Common Stock on such Trading Day as reported in composite transactions for the principal U.S. national or regional securities exchange on which the Common Stock is then listed. If the Common Stock is not listed on a U.S. national or regional securities exchange on such Trading Day, then the Last Reported Sale Price will be the last quoted bid price per share of Common Stock on such Trading Day in the over-the-counter market as reported by OTC Markets Group Inc. or a similar organization. If the Common Stock is not so quoted on such Trading Day, then the Last Reported Sale Price will be the average of the mid-point of the last bid price and the last ask price per share of Common Stock on such Trading Day from each of at least three nationally recognized independent investment banking firms the Company selects.

“Mandatory Exercise” has the meaning set forth in Section 6(a).

“Mandatory Exercise Condition” has the meaning set forth in Section 6(a).

“Mandatory Exercise Date” means an Exercise Date designated with respect to any Warrant pursuant to Section 6(a).

“Mandatory Exercise Notice” has the meaning set forth in Section 6(b).

“Mandatory Exercise Notice Date” means, with respect to a Mandatory Exercise, the date on which the Company sends the Mandatory Exercise Notice for such Mandatory Exercise pursuant to Section 6(b).

“Mandatory Exercise Right” has the meaning set forth in Section 6(a).

“Market Disruption Event” means, with respect to any date, the occurrence or existence, during the one-half hour period ending at the scheduled close of trading on such date on the principal U.S. national or regional securities exchange or other market on which the Common Stock is listed for trading or trades, of any material suspension or limitation imposed on trading (by reason of movements in price exceeding limits permitted by the relevant exchange or otherwise) in the Common Stock or in any options contracts or futures contracts relating to the Common Stock.

“Optional Exercise” means the exercise of any Warrant other than a Mandatory Exercise.

“Optional Exercise Date” means, with respect to the Optional Exercise of any Warrant, the first Business Day on which the requirements set forth in Section 5(a) for such Optional Exercise are satisfied.

“Permitted Transferee” means, with respect to any Holder: (a) any Affiliate of such Holder; (b) any limited partner, member, stockholder or other direct or indirect equity holder of such Holder, in connection with a distribution in-kind of securities by such Holder (including upon dissolution or liquidation of such Holder or any fund of which such Holder is an Affiliate); or (c) any successor entity resulting from a merger, consolidation, reorganization or similar transaction involving such Holder in which substantially all of the assets of such Holder are transferred to such successor; provided, that in each case any such Permitted Transferee agrees in writing to be bound by the terms of this Warrant Agreement.

“Person” or “person” means any individual, corporation, partnership, limited liability company, joint venture, association, joint-stock company, trust, unincorporated organization or government or other agency or political subdivision thereof.

“Physical Certificate” means any certificate (other than an Electronic Certificate), which may be represented in .pdf format only, representing any Warrants, which certificate is substantially in the form set forth in Exhibit A, registered in the name of the Holder of such Warrants and duly executed by the Company.

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“Register” has the meaning set forth in Section 3(e).

“Registration Rights Agreement” means that certain registration rights agreement dated the date hereof between the Company and FIT, as may be amended from time to time.

“Second Tranche Deposit” means the payment by the Holder (or its Affiliates) of a non-refundable deposit for the second tranche of 125 MW of Block Systems pursuant to the Commercial Agreement.

“Second Tranche Exercise Period” means the period from, and including, the Second Tranche Vesting Date to, and including, the Exercise Period Expiration Date applicable to the Second Tranche Warrants.

“Second Tranche Vesting Date” means the date on which the Second Tranche Vesting Event occurs.

“Second Tranche Vesting Event” means the Company’s receipt of the Second Tranche Deposit.

“Second Tranche Warrants” has the meaning set forth in Section 3(a).

“Securities Act” means the U.S. Securities Act of 1933, as amended.

“Strike Price” initially means $26.44 per share; provided, however, that the Strike Price is subject to adjustment pursuant to Section 13. Each reference in this Warrant Agreement or any Certificate to the Strike Price as of a particular date without setting forth a particular time on such date will be deemed to be a reference to the Strike Price immediately after the Close of Business on such date.

“Third Tranche Deposit” means the payment by the Holder (or its Affiliates) of a non-refundable deposit for the third tranche of 125 MW of Block Systems pursuant to the Commercial Agreement.

“Third Tranche Exercise Period” means the period from, and including, the Third Tranche Vesting Date to, and including, the Exercise Period Expiration Date applicable to the Third Tranche Warrants.

“Third Tranche Vesting Date” means the date on which the Third Tranche Vesting Event occurs.

“Third Tranche Vesting Event” means the Company’s receipt of the Third Tranche Deposit.

“Third Tranche Warrants” has the meaning set forth in Section 3(a).

“Trading Day” means any day on which (a) trading in the Common Stock generally occurs on the principal U.S. national or regional securities exchange on which the Common Stock is then listed or, if the Common Stock is not then listed on a U.S. national or regional securities exchange, on the principal other market on which the Common Stock is then traded; and (b) there is no Market Disruption Event. If the Common Stock is not so listed or traded, then “Trading Day” means a Business Day.

“Underlying Shares” initially means, with respect to any Warrant, that number of shares of Common Stock identified as the initial number of “Underlying Shares” in the Certificate representing such Warrant, subject to Vesting thereof; provided, however, that (a) the number of Underlying Shares of each Warrant will be subject to adjustment pursuant to Section 13, and (b) upon the Exercise of any Warrant (or any portion thereof representing less than all of the Underlying Shares thereof), the number of Underlying Shares of such Warrant will be reduced, effective as of the time such Warrant ceases to be outstanding, by the number of Underlying Shares so Exercised.

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“Valuation Price” means, with respect to the Exercise of any Warrant, the Last Reported Sale Price per share of Common Stock on the Exercise Date for such Exercise (or, if such Exercise Date is not a Trading Day, the immediately preceding Trading Day).

“Vested” means, with respect to any Warrant, that the applicable Vesting Event for such Warrant has occurred, and “Vesting” shall have a correlative meaning.

“Vesting Event” means (a) with respect to the First Tranche Warrants, the First Tranche Vesting Event; (b) with respect to the Second Tranche Warrants, the Second Tranche Vesting Event; and (c) with respect to the Third Tranche Warrants, the Third Tranche Vesting Event.

“VWAP” means, for the Common Stock for any Trading Day, the per share volume-weighted average price of the Common Stock as displayed under the heading “Bloomberg VWAP” on Bloomberg page “FCEL AQR” (or, if such page is not available, its equivalent successor page) in respect of the period from the scheduled open of trading until the scheduled close of trading of the primary trading session on such Trading Day (or, if such volume-weighted average price is unavailable, the market value of one share of Common Stock on such Trading Day as determined, using a volume-weighted average price method, by a nationally recognized independent investment banking firm retained for this purpose by the Company).

“Warrant” means each warrant issued by the Company pursuant to, and having the terms, and conferring to the Holders thereof the rights, set forth in, this Warrant Agreement. Subject to the terms of this Warrant Agreement, each Warrant will be Exercisable for shares of Common Stock based on the number of Vested Underlying Shares of such Warrant and the Strike Price.

“Warrant Agreement” means this Warrant Agreement, as amended or supplemented from time to time.

For purposes of this Warrant Agreement: (a) “or” is not exclusive; (b) “including” means “including without limitation”; (c) “will” expresses a command; (d) the “average” of a set of numerical values refers to the arithmetic average of such numerical values; (e) words in the singular include the plural and in the plural include the singular, unless the context requires otherwise; (f) “herein,” “hereof” and other words of similar import refer to this Warrant Agreement as a whole and not to any particular section or other subdivision of this Warrant Agreement, unless the context requires otherwise; (g) references to currency mean the lawful currency of the United States of America, unless the context requires otherwise; and (h) the exhibits and schedules to this Warrant Agreement are deemed to form part of this Warrant Agreement.

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For the avoidance of doubt, the number of Underlying Shares of each of the First Tranche Warrant, Second Tranche Warrant and Third Tranche Warrant is subject to adjustment pursuant to Section 13.

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“THE OFFER AND SALE OF THIS SECURITY AND THE SHARES OF COMMON STOCK ISSUABLE UPON EXERCISE OF THIS SECURITY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND THIS SECURITY AND SUCH SHARES MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED EXCEPT (A) PURSUANT TO A REGISTRATION STATEMENT THAT IS EFFECTIVE UNDER THE SECURITIES ACT; OR (B) PURSUANT TO AN EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT.”

“TRANSFERS, PLEDGES OR OTHER DISPOSITIONS HEREOF, OR OF ANY BENEFICIAL INTEREST HEREIN, ARE SUBJECT TO RESTRICTIONS SET FORTH IN THE WARRANT AGREEMENT REFERRED TO HEREIN. ANY PURPORTED TRANSFER, PLEDGE OR OTHER DISPOSITION IN VIOLATION OF SUCH RESTRICTIONS WILL BE VOID AND OF NO FORCE OR EFFECT.”

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Notwithstanding anything to the contrary in this Warrant Agreement, no shares of Common Stock will be issued or delivered upon Exercise of any Warrant of any Holder, and no Warrant of any Holder will be Exercisable, in each case to the extent, and only to the extent, that such issuance, delivery, Exercise or exercisability would result in such Holder, or a “person” or “group” (within the meaning of Section 13(d)(3) of the Exchange Act) that includes such Holder, beneficially owning, after giving effect to the issuance of the shares of Common Stock to be issued upon such Exercise, in excess of nineteen and ninety-nine hundredths percent (19.99%) of the then-outstanding shares of Common Stock as so increased.

Subject to the first sentence of Section 5(b), the Holder shall not be entitled to vote or receive dividends or be deemed the holder of Common Stock or any other securities of the Company that may at any time be issuable on the exercise of any Warrant for any purpose, nor shall anything contained herein be construed to confer upon the Holder, as such, any of the rights of a stockholder of the Company or any right to vote for the election of directors or upon any matter submitted to stockholders at any meeting thereof, or to give or withhold consent to any corporate action (whether upon any recapitalization, issuance of stock, reclassification of stock, change of par value, or change of stock to no par value, consolidation, merger, conveyance, or otherwise) or to receive notice of meetings, or to receive dividends or subscription rights or otherwise until such Warrant shall have been exercised as provided herein.

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The Company covenants that during the period any Warrant is outstanding and Exercisable, the Company will reserve from its authorized and unissued Common Stock a sufficient number of shares to provide for the issuance of Common Stock upon the Vesting and exercise of all Warrants then outstanding. The Company further covenants that all shares that may be issued upon the exercise of rights represented by any Warrant, all as set forth herein, will be duly authorized, validly issued, fully paid and nonassessable and shall be free from all preemptive rights, taxes, liens and charges in respect of the issue thereof (other than taxes in respect of any transfer occurring contemporaneously or otherwise specified herein). The Company agrees that its issuance of any Warrant shall constitute full authority to its officers who are charged with the duty of executing stock certificates or registering book-entry shares to execute and issue the necessary certificates or register the necessary book-entry shares for shares of Common Stock upon the exercise of any Warrant.

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then, and in each such case, the Company will promptly send notice to the Holder(s) specifying, as the case may be, (A) the date on which a record is to be taken for the purpose of such dividend, distribution or right, and stating the amount and character of such dividend, distribution or right, or (B) the date on which such reorganization, reclassification, consolidation, merger, conveyance, dissolution, liquidation or winding-up is to take place, and the time, if any is to be fixed, as of which the holders of record of Common Stock (or such stock or securities at the time receivable upon the exercise of any Warrant) shall be entitled to exchange their shares of Common Stock (or such other stock or securities) for securities or other property deliverable upon such reorganization, reclassification, consolidation, merger, conveyance, dissolution, liquidation or winding-up. Such notice shall be mailed at least fifteen (15) days prior to the date therein specified.

The Strike Price and the number of shares purchasable hereunder are subject to adjustment from time to time as follows:

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The Underlying Shares issued upon exercise of this Warrant shall benefit from certain resale shelf registration rights as set forth in the Registration Rights Agreement.

This Warrant shall be governed by and construed in accordance with the laws of the State of Delaware.

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IN WITNESS WHEREOF, FUELCELL ENERGY, INC. and FIT ENERGY USA LP have caused this Warrant Agreement to be executed by their respective officers thereunto duly authorized as of the date first written above.

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EXHIBIT A

FORM OF WARRANT

THE OFFER AND SALE OF THIS SECURITY AND THE SHARES OF COMMON STOCK ISSUABLE UPON EXERCISE OF THIS SECURITY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND THIS SECURITY AND SUCH SHARES MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED EXCEPT (A) PURSUANT TO A REGISTRATION STATEMENT THAT IS EFFECTIVE UNDER THE SECURITIES ACT; OR (B) PURSUANT TO AN EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT.”

“TRANSFERS, PLEDGES OR OTHER DISPOSITIONS HEREOF, OR OF ANY BENEFICIAL INTEREST HEREIN, ARE SUBJECT TO RESTRICTIONS SET FORTH IN THE WARRANT AGREEMENT REFERRED TO HEREIN. ANY PURPORTED TRANSFER, PLEDGE OR OTHER DISPOSITION IN VIOLATION OF SUCH RESTRICTIONS WILL BE VOID AND OF NO FORCE OR EFFECT.

FuelCell Energy, Inc.

Warrants

Certificate No. [___]

FuelCell Energy, Inc., a Delaware corporation (the “Company”), certifies that [___] is the registered owner of the Warrant represented by this certificate (this “Certificate”). The initial number of Underlying Shares of the Warrant represented by this Certificate is [___] shares of Common Stock, which number is subject to adjustment as provided in the Warrant Agreement referred to below. This Warrant represents a [First]/[Second]/[Third] Tranche Warrant (as defined in the Warrant Agreement).

The terms of the Warrants are set forth in the Warrant Agreement, dated as of June 22, 2026, between the Company and FIT Energy USA LP (the “Warrant Agreement”). Capitalized terms used in this Certificate without definition have the respective meanings ascribed to them in the Warrant Agreement.

Additional terms of this Certificate are set forth on the other side of this Certificate.

[The Remainder of This Page Intentionally Left Blank; Signature Page Follows]

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IN WITNESS WHEREOF, FuelCell Energy, Inc. has caused this instrument to be duly executed as of the date set forth below.

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FuelCell Energy, Inc.

Warrant

This Certificate represents a duly issued and outstanding Warrant having an initial number of Underlying Shares as set forth on the face of this Certificate. Certain terms of the Warrants are summarized below. Notwithstanding anything to the contrary in this Certificate, to the extent that any provision of this Certificate conflicts with the provisions of the Warrant Agreement, the provisions of the of the Warrant Agreement will control. This Warrant represents a [First]/[Second]/[Third] Tranche Warrant (as defined in the Warrant Agreement).

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To request a copy of the Warrant Agreement, which the Company will provide to any Holder at no charge, please send a written request to the following address:

FuelCell Energy, Inc.

3 Great Pasture Road,

Danbury, Connecticut

Attention: Amanda Schreiber

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EXHIBIT B

NOTICE OF EXERCISE

 To: FUELCELL ENERGY, INC.

 (1)           The undersigned hereby elects to purchase                    shares of Common Stock of FuelCell Energy, Inc. (the “Company”), pursuant to the terms of the Warrant Agreement, dated as of June 22, 2026, between the Company and FIT Energy USA LP (the “Warrant Agreement”), and tenders herewith payment of the Aggregate Strike Price for such shares in full by wire transfer of immediately available funds.

 (2)           Please issue a certificate or certificates representing said shares of Common Stock in the name of the undersigned or in such other name as is specified below:

 (3)           Please issue a new Warrant for the unexercised portion of the attached Warrant in the name of the undersigned or in such other name as is specified below.

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Exhibit 10.1

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REGISTRATION RIGHTS AGREEMENT

by and among

FUELCELL ENERGY, INC.,

AND

THE OTHER HOLDERS FROM TIME TO TIME PARTIES
HERETO

Dated as of June 22, 2026

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TABLE OF CONTENTS

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REGISTRATION RIGHTS AGREEMENT

This REGISTRATION RIGHTS AGREEMENT (this “Agreement”), dated as of June 22, 2026, is by and among (i) FuelCell Energy, Inc., a Delaware corporation (“Company”) and the Holders (as defined herein) party hereto for which an authorized signatory has provided a signature across from such Holder’s name on Schedule A hereto (each a “Party” and, collectively, the “Parties”).

WHEREAS, the Company has entered into that certain Warrant Agreement (the “Warrant Agreement”) with FIT Energy USA LP, a Delaware limited partnership (“FIT”) and the Holders, dated the date hereof, and has agreed to provide the Holders with certain resale shelf registration rights with respect to the Registrable Securities (as hereinafter defined) received by the Holders pursuant to the Warrant Agreement; and

NOW THEREFORE, in consideration of the mutual covenants and agreements contained herein, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, and intending to be legally bound hereby, the parties hereto mutually agree as follows:

“1933 Act” means the Securities Act of 1933, as amended.

“1934 Act” means the Securities Exchange Act of 1934, as amended.

“Affiliate” of any specified Person means any other Person directly or indirectly controlling, controlled by or under direct or indirect common control with such specified Person.  For the purposes of this definitions “control” when used with respect to any Person means the power to direct the management and policies of such Persons directly or indirectly, whether through the ownership of voting securities, by contract or otherwise; and the terms “controlling” and “controlled” have meanings correlative to the foregoing; provided, that (i) “Affiliate” shall not include any portfolio company of any specified Person and (ii) with respect to the Company, “Affiliates” means the Company and any Person that is controlled, directly or indirectly, by the Company.

“Business Day” means each Monday, Tuesday, Wednesday, Thursday and Friday that is not a day on which banking institutions in the City of New York are authorized or obligated by law or executive order to close.

“Commission” means the U. S. Securities and Exchange Commission.

“Common Stock” means the shares of common stock, par value $0.0001 per share, of the Company (NASDAQ:FCEL).

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“Holder” means any holder from time to time of Registrable Securities that is a Party to this Agreement.

“Joinder Agreement” means a joinder agreement to this Agreement, a form of which is attached hereto as Exhibit A.

“Permitted Transferee” means, with respect to any Holder: (a) any Affiliate of such Holder; (b) any limited partner, member, stockholder or other direct or indirect equity holder of such Holder, in connection with a distribution in-kind of securities by such Holder (including upon dissolution or liquidation of such Holder or any fund of which such Holder is an Affiliate); or (c) any successor entity resulting from a merger, consolidation, reorganization or similar transaction involving such Holder in which substantially all of the assets of such Holder are transferred to such successor.

“Person” means an individual, a corporation, a partnership, limited liability entity, an association, a trust or any other entity or organization, including a government, a political subdivision or an agency or instrumentality thereof.

“Registrable Securities” means (i) the Common Stock issuable to a Holder upon exercise of a Warrant received by such Holder pursuant to the Warrant Agreement and (ii) any other common securities issued and issuable therefor or with respect thereto, whether by way of stock split, stock dividend, reclassification, subdivision or reorganization, recapitalization, merger, consolidation, distribution or similar event (it being understood that, for purposes of this Agreement, a Person shall be deemed to be a Holder of Registrable Securities whenever such Person in its sole discretion has the right to then acquire or obtain from the Company any Registrable Securities, whether or not such acquisition or other transfer has actually been effected). As to any particular Registrable Securities, such securities shall cease to constitute Registrable Securities when (1) a registration statement with respect to the offering of such securities by the Holder thereof shall have been declared effective under the 1933 Act and such securities shall have been sold, transferred or disposed of pursuant to such registration statement, (2) such securities have been sold pursuant to a Rule 144 Transfer, (3) such securities shall have been repurchased by the Company or ceased to be outstanding, (4) such securities shall have been otherwise transferred by such Holder to an entity or Person that is not a Permitted Transferee of such Holder, new certificates for such securities not bearing (or book-entry positions not subject to) a 1933 Act legend restricting further transfer shall have been delivered by the Company and subsequent disposition of them shall not require registration or qualification of them under the 1933 Act or any state securities or blue sky law then in effect or (5) such Holder is able to dispose of all of its Registrable Securities pursuant to Rule 144 without volume limitation or other restrictions on transfer thereunder and without the requirement for the Company to be in compliance with Rule 144(c)(1).

“Rule 144” means Rule 144 under the 1933 Act (or any successor Rule).

“Rule 144 Transfer” means any transfer for value conducted in accordance with Rule 144 (or any successor rule promulgated thereafter by the Commission).

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“Warrant” means each warrant issued by the Company pursuant to, and having the terms, and conferring to the holders thereof the rights set forth in, the Warrant Agreement.

TermSection

AdviceSection 2.02

AgreementPreamble

Blackout PeriodSection 2.06

CompanyPreamble

Filing DeadlineSection 2.01 (a)

Opt-Out RequestSection 3.01

Shelf RegistrationSection 2.01 (a)

Shelf Registration StatementSection 2.01 (a)

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The Holders, upon receipt of any notice from the Company of the happening of any event of the kind described in Section 2.02(d) will forthwith discontinue disposition of the securities until the Holders’ receipt of the copies of the supplemented or amended prospectus contemplated by Section 2.02(d) or until it is advised in writing (the “Advice”) by the Company that the use of the prospectus may be resumed, and has received copies of any additional or supplemental filings which are incorporated by reference in the prospectus, and, if so directed by the Company, each Holder will deliver to the Company (at the Company’s sole expense) all copies, other than permanent file copies then in such Holder’s possession, of the prospectus covering such securities current at the time of receipt of such notice.

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EACH SUCH NOTICE, REQUEST OR OTHER COMMUNICATION SHALL BE EFFECTIVE (I) IF GIVEN BY EMAIL OR FACSIMILE, WHEN SUCH MESSAGE IS TRANSMITTED TO THE ADDRESS OR NUMBER SPECIFIED ON THE SIGNATURE PAGES TO THIS AGREEMENT OR ANY JOINDER AGREEMENT, (II) IF delivered by overnight courier, the earlier of the first Business Day following the date sent by such overnight courier or upon receipt, (iii) if given by mail, three (3) Business Days after such communication is deposited in the mails registered or certified, return receipt requested, with postage prepaid, addressed as aforesaid, or (iv) if given by any other means, when delivered at the address specified on the signature pages to this Agreement or any Joinder Agreement. Each Holder shall have the right, at any time and from time to time, to elect to not receive any notice that the Company or any other Holders otherwise are required to deliver pursuant to this Agreement by delivering to the Company a written statement signed by such Holder that it does not want to receive any notices hereunder (an “Opt-Out Request”); in which case and notwithstanding anything to the contrary in this Agreement the Company and other Holders shall not be required to, and shall not, deliver any notice or other information required to be provided to Holders hereunder to the extent that the Company or such other Holders reasonably expect would result in a Holder acquiring material non-public information. An Opt-Out Request may state a date on which it expires or, if no such date is specified, shall remain in effect indefinitely. A Holder who previously has given the Company an Opt-Out Request may revoke such request at any time, and there shall be no limit on the ability of a Holder to issue and revoke subsequent Opt-Out Requests; provided that each Holder shall use commercially reasonable efforts to minimize the administrative burden on the Company arising in connection with any such Opt-Out Requests.

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Any such permitted assignment or transfer shall not be deemed to terminate or otherwise affect any rights or obligations under this Agreement, and all references herein to the “Holder” shall be deemed to include such permitted assigns.

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[Signature Pages Follow]

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IN WITNESS WHEREOF, the undersigned have caused this Agreement to be executed as of the date first written above.

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FUELCELL ENERGY, INC.

By: /s/ Jason Few Name: Jason Few Title: President & Chief Executive SIGNATURE PAGE AND JOINDER AGREEMENT TO REGISTRATION RIGHTS AGREEMENT

Officer

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[Signature Page to Registration Rights Agreement]

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Schedule A

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[Signatures and Notice Information]

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EXHIBIT A

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By executing and delivering this Signature Page and Joinder Agreement, the undersigned hereby agrees, to (i) become a party to that certain Registration Rights Agreement, dated as of the date hereof (as amended, modified or supplemented from time to time in accordance with the terms thereof, the “Registration Rights Agreement”), by and among FuelCell Energy, Inc., a Delaware corporation, and the other parties thereto and (ii) be deemed to be and be bound as a Holder (as defined in the Registration Rights Agreement) with such rights (and related obligations and liabilities) in respect of the Registrable Securities (as defined in the Registration Rights Agreement) being acquired by the undersigned in connection with the execution of this Signature Page and Joinder Agreement and subject to the terms and conditions of the Registration Rights Agreement as if an original party thereto.

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By: /s/ Sam Pai Name: Sam Pai Title: General Partner FuelCell Energy and Fit Energy Announce Strategic Agreement for up to 380 MW of Clean Power for Data Centers

Notice Address:

FIT ENERGY USA LP

701 Pk Commerce Blvd

Boca Raton, FL 33487

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Email:

Exhibit 99.1

FOR IMMEDIATE RELEASE

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Initial 30 MW delivery is expected to begin this year.

Danbury, Conn., and Boca Raton, Fla., June 23, 2026 (GLOBE NEWSWIRE) – FuelCell Energy, Inc. (Nasdaq: FCEL), a clean energy technology company that manufactures utility scale power solutions, and Fit Energy USA LP (“Fit Energy”), a developer of reliable power solutions to support advanced computing infrastructure and artificial intelligence, today announced a strategic agreement for up to 380 megawatts (MW) of clean, baseload on-site power for data centers using FuelCell Energy’s utility-scale fuel cell technology. The agreement includes an immediate deposit for an initial 30 MW of power scheduled to begin delivery later this year.

“We are pleased to partner with Fit Energy on its development plans. We’ve engaged with a diverse range of prospective customers across the digital infrastructure landscape, and Fit Energy has distinguished itself through its commitment to ‘energy as a service’ power solutions that support both communities and the environment,” said Jason Few, President and CEO of FuelCell Energy. He added, “This agreement further validates our decision to scale our operations to 500 MW, preserving our ability to serve a broad and growing pipeline of customers.”

Joel Leonoff, CEO of Fit Energy, added, “Today’s announcement marks a critical step in building the power foundation required for the next generation of AI infrastructure. FuelCell Energy’s technology aligns with our growth objectives and our goal of delivering behind-the-meter power solutions to data centers at gigawatt scale.”

Under the arrangement, Fit Energy will be eligible to receive warrants tied to future deployment milestones of up to 380 MW. The warrant structure is designed to align long-term value creation with successful project execution and customer deployment.

Canaccord Genuity served as a financial advisor to FuelCell Energy Inc. on certain aspects of this transaction.

About Fit Energy

Fit Energy is an energy infrastructure company focused on long-term ownership of generation assets formed to deliver near-term, scaled energy solutions for the digital economy. The platform is designed to serve large power requirements through a hybrid model supporting behind-the-meter, microgrid and grid-connected structures ranging from fuel cell technology to natural gas turbines. Learn more about Fit Energy at www.Fitenergygroup.com.

About FuelCell Energy

FuelCell Energy, Inc. (Nasdaq: FCEL) is an American clean energy technology company delivering continuous, scalable baseload power for mission critical applications globally. The company’s fuel cell systems generate electricity directly at the point of use, enabling reliable, low emissions power for data centers, industrial facilities, utilities, and distributed generation customers.

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FuelCell Energy delivers commercially proven, modular, utility-scale systems—backed by global fuel cell deployments approaching one gigawatt. Learn more at www.fuelcellenergy.com.

Cautionary Language

This news release contains forward-looking statements within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 regarding future events or our future financial performance that involve certain contingencies and uncertainties. The forward-looking statements include, without limitation, statements with respect to the Company’s anticipated financial results and statements regarding the Company’s plans and expectations regarding the continuing development, commercialization and financing of its current and future fuel cell technologies, the Company’s business plans and strategies, the Company’s plan to reduce operating costs, the capabilities of the Company’s products, the Company’s potential sales pipeline, opportunities, and partners, and the markets in which the Company expects to operate. Projected and estimated numbers contained herein are not forecasts and may not reflect actual results. These forward-looking statements are not guarantees of future performance, and all forward-looking statements are subject to risks and uncertainties, known and unknown, that could cause actual results and future events to differ materially from those projected. Factors that could cause such a difference include, without limitation: general risks associated with product development and manufacturing; general economic conditions; changes in interest rates, which may impact project financing; supply chain disruptions; changes in the utility regulatory environment; changes in the utility industry and the markets for distributed generation, distributed hydrogen, and fuel cell power plants configured for carbon capture or carbon separation; potential volatility of commodity prices that may adversely affect our projects; availability of government subsidies and economic incentives for alternative energy technologies; our ability to remain in compliance with U.S. federal and state and foreign government laws and regulations; our ability to maintain compliance with the listing rules of The Nasdaq Stock Market; rapid technological change; competition; the risk that our bid awards will not convert to contracts or that our contracts will not convert to revenue; market acceptance of our products; changes in accounting policies or practices adopted voluntarily or as required by accounting principles generally accepted in the United States; factors affecting our liquidity position and financial condition; government appropriations; the ability of the government and third parties to terminate their development contracts at any time; the ability of the government to exercise “march-in” rights with respect to certain of our patents; our ability to successfully market and sell our products internationally; delays in our timeline for bringing commercially viable products to market; our ability to develop additional commercially viable products in the future; our ability to implement our strategy; our ability to reduce our levelized cost of energy and deliver on our cost reduction strategy generally; our ability to protect our intellectual property; litigation and other proceedings; the risk that commercialization of our new products will not occur when anticipated or, if it does, that we will not have adequate capacity to satisfy demand; our need for and the availability of additional financing; our ability to generate positive cash flow from operations; our ability to service our long-term debt; our ability to increase the output and longevity of our platforms and to meet the performance requirements of our contracts; our ability to expand our customer base and maintain relationships with our largest customers and strategic business allies; and our ability to reduce operating costs, as well as other risks set forth in the Company’s filings with the Securities and Exchange Commission, including the Company’s Annual Report on Form 10-K for the fiscal year ended October 31, 2025. The forward-looking statements contained herein speak only as of the date of this press release. The Company expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any such statement contained herein to reflect any change in the Company’s expectations or any change in events, conditions or circumstances on which any such statement is based.

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