Eos Energy Enterprises, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Schedule 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

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Filed by a party other than the Registrant☐

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☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☒ Definitive Proxy Statement

☐ Definitive Additional Materials

☐ Soliciting Material Under §240.14a-12

EOS ENERGY ENTERPRISES, INC.

(Exact Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

☒ No fee required.

☐ Fee paid previously with preliminary materials.

☐ Fee computed on table in exhibit required by Item 25 (b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

3920 Park Avenue

Edison, New Jersey 08820

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 15, 2025

To the Stockholders of Eos Energy Enterprises, Inc.:

NOTICE IS HEREBY GIVEN that the Annual Meeting of Stockholders (the “Annual Meeting”) of Eos Energy Enterprises, Inc., a Delaware corporation (the “Company”), will be a virtual meeting conducted exclusively via live webcast at www.virtualshareholdermeeting.com/EOSE2025 on May 15, 2025, at 10:00 a.m. Eastern time for the following purposes:

1. to elect three directors as Class II directors of Eos Energy Enterprises, Inc., each to serve for three years and until his successor has been elected and qualified, or until his earlier death, resignation or removal;

2. to ratify the selection of Deloitte & Touche LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2025;

3. to approve a non-binding advisory resolution approving the compensation of the named executive officers; and

4. to approve an amendment to our Second Amended and Restated 2020 Incentive Plan.

The Company will also transact such other business as may properly come before the Annual Meeting or any adjournment or postponement thereof.

The foregoing items of business are more fully described in the Proxy Statement accompanying this Notice of Annual Meeting of Stockholders. Only stockholders who owned common stock of the Company at the close of business on March 19, 2025 (the “Record Date”) can vote at this meeting or any adjournments that take place. The Company will begin mailing the Notice of Internet Availability to our stockholders of record as of the Record Date for the first time on or about March 27, 2025.

The Board of Directors recommends that you vote:

Proposal 1: FOR the election of the three director nominees;

Proposal 2: FOR the ratification of the appointment of Deloitte & Touche LLP, as the independent registered public accounting firm;

Proposal 3: FOR the approval of the non-binding advisory resolution to approve the compensation of our named executive officers; and

Proposal 4: FOR an amendment to our Second Amended and Restated 2020 Incentive Plan.

2025 Virtual Annual Stockholder Meeting

The Board of Directors has determined to hold the annual meeting virtually in order to facilitate stockholder attendance and participation by stockholders from all locations at no cost. We believe this is the right choice for the Company at this time, as it enables engagement with our stockholders, regardless of size, resources, or physical location while safeguarding the health of our stockholders, Board, and management. We are committed to ensuring that stockholders will be afforded the same rights and opportunities to participate as they would at an in-person meeting. You will be able to attend the meeting online, vote your shares electronically and submit questions during the meeting by visiting www.virtualshareholdermeeting.com/EOSE2025 at the meeting date and time. The meeting webcast will begin promptly at 10:00 a.m. Eastern Time. We encourage you to access the meeting prior to the start time. Online check-in will begin at 9:45 a.m. Eastern Time, and you should allow ample time for the check-in procedures. If you experience technical difficulties during the check-in process or during the meeting, please call the technical support number that will be posted on the virtual Annual Meeting login page for assistance. Technical assistance will be available through the conclusion of the Annual Meeting.

YOUR VOTE IS IMPORTANT. WHETHER OR NOT YOU PLAN TO ATTEND THE VIRTUAL MEETING ONLINE, WE ENCOURAGE YOU TO READ THE ACCOMPANYING PROXY STATEMENT AND OUR ANNUAL REPORT ON FORM 10-K FOR THE FISCAL YEAR ENDED DECEMBER 31, 2024, AND SUBMIT YOUR PROXY AS SOON AS POSSIBLE USING ONE OF THE THREE CONVENIENT VOTING METHODS DESCRIBED IN “INFORMATION ABOUT THE PROXY PROCESS AND VOTING” IN THE PROXY STATEMENT. IF YOU RECEIVE MORE THAN ONE SET OF PROXY MATERIALS OR NOTICE OF INTERNET AVAILABILITY BECAUSE YOUR SHARES ARE REGISTERED IN DIFFERENT NAMES OR ADDRESSES, EACH PROXY SHOULD BE SIGNED AND SUBMITTED TO ENSURE THAT ALL OF YOUR SHARES WILL BE VOTED.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 15, 2025

The Notice of Annual Meeting of Stockholders to be held on May 15, 2025, the accompanying Proxy Statement and the Company’s 2024 Annual Report on Form 10-K are available, free of charge, athttp://www.proxyvote.com.

The Notice contains instructions on how to access our proxy materials and vote over the internet at www.proxyvote.com and how stockholders can receive a paper copy of our proxy materials, including the accompanying Proxy Statement, a proxy card or voting instruction card and our fiscal year ended December 31, 2024 Annual Report on Form 10-K. Stockholders can also request to receive future proxy materials in printed form by mail or electronically by email by contacting Investor Relations Department at 862-207-7955 or email ir@eose.com.

By Order of the Board of Directors

/s/Michael Willis Silberman

Michael Willis Silberman

Chief Legal Officer and Corporate Secretary

March 27, 2025

TABLE OF CONTENTS

3920 PARK AVENUE

EDISON, NEW JERSEY 08820

PROXY STATEMENT

FOR THE 2025 ANNUAL MEETING OF STOCKHOLDERS

MAY 15, 2025

We have made available our proxy materials because the Board of Directors (the “Board”) of Eos Energy Enterprises, Inc. (referred to herein as the “Company,” “Eos,” “we,” “us” or “our”) is soliciting your proxy to vote at our 2025 Annual Meeting of Stockholders (the “Annual Meeting”) to be held on May 15, 2025, at 10:00 a.m. Eastern Time, atwww.virtualshareholdermeeting.com/EOSE2025.

◦This Proxy Statement summarizes information about the proposals to be considered at the Annual Meeting and other information you may find useful in determining how to vote.

◦The Proxy Card is the means by which you actually authorize another person to vote your shares in accordance with your instructions.

In addition to solicitations by mail, our directors, officers and employees, without additional remuneration, may solicit proxies by telephone, e-mail and personal interviews. All costs of solicitation of proxies will be borne by us. Brokers, custodians and fiduciaries will be requested to forward proxy soliciting material to the owners of stock held in their names, and we will reimburse them for their reasonable out-of-pocket expenses incurred in connection with the distribution of proxy materials.

Pursuant to the rules adopted by the Securities and Exchange Commission (the “SEC”), we have elected to provide access to our Annual Meeting materials, which include this Proxy Statement and our Annual Report on Form 10-K for the fiscal year ended December 31, 2024 (the “Form 10-K”), over the internet in lieu of mailing printed copies. We will begin mailing the Notice of Internet Availability to our stockholders of record as of March 19, 2025 (the “Record Date”) for the first time on or about April 4, 2025.

The Notice of Internet Availability will contain instructions on how to access and review the Annual Meeting materials and will also contain instructions on how to request a printed copy of the Annual Meeting materials. Additionally, we have provided brokers, dealers, banks, voting trustees and their nominees, at our expense, with additional copies of our proxy materials and our Annual Report on Form 10-K so that they can supply these materials to the beneficial owners of shares of our common stock as of the Record Date. Our Annual Report on Form 10-K and the 2025 Proxy Statement are available, free of charge, at proxyvote.com.