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

Filed by the Registrant☒

Filed by a party other than the Registrant☐

Check the appropriate box:

☐ 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.

Stockholder Engagement

Proxy StatementFor the 2026 Annual Meeting of StockholdersJune 3, 2026

3920 Park Avenue

Edison, New Jersey 08820

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 2026 Annual Meeting of Stockholders (the “Annual Meeting”) to be held on June 3, 2026, at 10:00 a.m. Eastern Time, at www.virtualshareholdermeeting.com/EOSE2026.

•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, 2025 (the “Form 10-K”), over the internet in lieu of mailing printed copies. 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 April 14, 2026.

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 2026 Proxy Statement are available, free of charge, at proxyvote.com.

Director Skills and Qualifications