ESS TECH INC

Item 1.01 Entry into a Material Definitive Agreement. On July 16, 2026, ESS Tech, Inc. (the “Company”) entered into an amendment to its Sales Agreement (the “Amendment Agreement”) for its “at the market offering” program (the “ATM Program”) to sell $75 million shares of the Company’s common stock (the “Shares”) which was previously entered into with Yorkville Ives & Co., LLC (formerly Yorkville Securities, LLC) (“Yorkville Ives”), BMO Capital Markets Corp. (“BMO”), Canaccord Genuity LLC (“Canaccord”), Needham & Company, LLC (“Needham”) and Stifel, Nicolaus & Company, Incorporated (“Stifel”) on November 13, 2025 (the “Original Sales Agreement”). Under the Amendment, the Company has (i) terminated the Original Sales Agreement with respect to BMO, Canaccord, Needham and Stifel; (ii) added Roth Capital Partners, LLC (“Roth”) as an additional sales agent under the Amended Sales Agreement (as defined below) and (iii) Roth has assumed the responsibilities of acting as a “qualified independent underwriter” within the meaning of Rule 5121 of the Financial Industry Regulatory Authority in connection with this offering, replacing Canaccord as “qualified independent underwriter” (collectively, the “Amendments”). The amended Original Sales Agreement is hereinafter referred to as the “Amended Sales Agreement.” In connection with the Amendments, the Company has filed an amendment to the prospectus supplement filed with the Securities and Exchange Commission (the “SEC”) on December 11, 2025 relating to the Company’s ATM Program. The foregoing summary of the Amendment Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Amendment Agreement, a copy of which is filed as Exhibit 1.1 hereto and incorporated herein by reference. The provisions of the Original Sales Agreement and Amendment Agreement, including the representations and warranties contained therein, are not for the benefit of any party other than the parties to such Original Sales Agreement and Amendment Agreement and are not intended as a document for investors and the public to obtain factual information about the Company’s current state of affairs. Rather, investors and the public should look to other disclosures contained in the Company’s filings with the SEC. This Current Report on Form 8-K shall not constitute an offer to sell or the solicitation of an offer to buy any Shares under the Amended Sales Agreement, nor shall there be any sale of such Shares in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. YA II PN, Ltd., an affiliate of Yorkville Ives, was a party to the Company’s Standby Equity Purchase Agreement, and an affiliate of Yorkville Ives is the lender under the Promissory Note between the Company and YA II PN, Ltd. Furthermore, Yorkville Ives and Roth and/or one of their respective affiliates may in the future provide certain commercial banking, financial advisory, and investment banking services in the ordinary course of business for the Company for which they will receive customary fees and commissions.