Fuelcell Energy Inc — Additional Proxy Materials (DEFA14A)

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Preliminary Proxy Statement

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material under §240.14a-12

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Your Vote Counts! Smartphone users Point your camera here and vote without entering a control number For complete information and to vote, visit www.ProxyVote.com Control # V83277-P40097 *Please check the meeting materials for any special requirements for meeting attendance. FUELCELL ENERGY, INC. 2026 Annual Meeting Vote by April 1, 2026 11:59 PM ET You invested in FUELCELL ENERGY, INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy materials for the stockholder meeting to be held on April 2, 2026. Vote Virtually at the Meeting* April 2, 2026 1:00 p.m. Eastern Daylight Time Virtually at: www.virtualshareholdermeeting.com/FCEL2026 Get informed before you vote View the Notice, Proxy Statement and Annual Report online OR you can receive a free paper or email copy of the material(s) by requesting prior to March 19, 2026. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. FUELCELL ENERGY, INC. 3 GREAT PASTURE ROAD DANBURY, CT 06810 ATTN: CORPORATE SECRETARY

Vote at www.ProxyVote.com Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Delivery Settings”. Voting Items Board Recommends V83278-P40097 THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. 1. To elect eight directors to serve until the 2027 Annual Meeting of Stockholders and until their successors are duly elected and qualified Nominees: 1a. James H. England For 1b. Jason Few For 1c. Matthew F. Hilzinger For 1d. Natica von Althann For 1e. Cynthia Hansen For 1f. Donna Sims Wilson For 1g. Betsy Bingham For 1h. Tyrone Michael Jordan For 2. To approve, on a non-binding advisory basis, the compensation of FuelCell Energy, Inc.’s named executive officers as set forth in the “Executive Compensation” section of the Proxy Statement For 3. To ratify the selection of KPMG LLP as FuelCell Energy, Inc.’s independent registered public accounting firm for the fiscal year ending October 31, 2026 For 4. To approve the amendment and restatement of the FuelCell Energy, Inc. Fifth Amended and Restated 2018 Omnibus Incentive Plan For 5. To approve the amendment and restatement of the FuelCell Energy, Inc. 2018 Employee Stock Purchase Plan, as amended and restated For NOTE: To transact such other business as may properly come before the Annual Meeting or any adjournment thereof.