ESS Tech Inc美股招股说明书(2025-10-07版)

630,000 Shares of Common Stock Pursuant to this prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectus datedNovember 17, 2022 (as supplemented from time to time, the “Prospectus”), we are offering 630,000 shares of our common stock toYA II PN, Ltd., a Cayman Islands exempt limited partnership (“Yorkville”), at a price of approximately $1.49 per share, pursuant toour previously announcedStandby Equity Purchase Agreement with Yorkville dated July 9, 2025 (the “SEPA”). These shares arebeing issued as part of the commitment by Yorkville to purchase from time to time shares of our common stock pursuant to the SEPA.The total purchase price of the shares is approximately $935,865. We intend to use the net proceeds to continue normal businessoperations related to our strategic pivot focused on the Energy Base product and ongoing contracting activities. We expect to issue theshares to Yorkville on or about October 7, 2025. In addition to our issuance of our shares to Yorkville pursuant to the SEPA, this Prospectus also covers the resale of these sharesby Yorkville to the public. Though we have been advised by Yorkville, and Yorkville represents in the SEPA, that Yorkville ispurchasing the shares for its own account, for investment purposes in which it takes investment risk (including, without limitation, therisk of loss), and without any view or intention to distribute such shares in violation of the Securities Act of 1933, as amended (the“Securities Act”), or any other applicable securities laws, the Securities and Exchange Commission (the “SEC”) may take the positionthat Yorkville may be deemed an “underwriter” within the meaning of Section 2(a)(11) of the Securities Act and any profits on thesales of shares of our common stock by Yorkville and any discounts, commissions or concessions received by Yorkville are deemed tobe underwriting discounts and commissions under the Securities Act. For additional information on the methods of sale that may beused by Yorkville, see the section entitled “Plan of Distribution” on page S-12 of the prospectus supplement dated July 11, 2025 andpage 33 of the base prospectus dated November 17, 2022. Our shares of common stock are listed on the NYSE under the symbol “GWH.” On October 6, 2025, the closing sale price of ourcommon stock was $2.01 per share. We are an “emerging growth company” and a “smaller reporting company” under federalsecurities laws and, as such, are subject to reduced public company reporting requirements. Investing in our common stock involves risks. Please read “Risk Factors,” beginning on page S-6 of the prospectussupplement dated July 11, 2025. Neither the SEC nor any other regulatory body has approved or disapproved of these securities or passed upon theaccuracy or adequacy of the Prospectus. Any representation to the contrary is a criminal offense. The date of this prospectus supplement is October 6, 2025. Neither we nor Yorkville have authorized anyone to provide you with any information other than the informationcontained in or incorporated by reference in this prospectus supplement, or the prospectus supplement dated July 11, 2025 andbase prospectus dated November 17, 2022 and in the documents incorporated by reference herein and therein. We andYorkville take no responsibility for, and can provide no assurance as to the reliability of, any other information that othersmay give you. We are not making an offer of these securities in any state or jurisdiction where the offer is not permitted. Youshould assume that the information contained in or incorporated by reference in this prospectus supplement, or the prospectussupplement dated July 11, 2025 and base prospectus dated November 17, 2022 is accurate only as of their respective dates. The Offering 630,000 shares of common stock of ESS Tech, Inc. Securities offeredCommon stockoutstanding after theofferingPurchaserPurchase priceProceedsUse of proceeds 16,020,884 YA II PN, Ltd. pursuant to the Standby Equity Purchase Agreement dated July 9, 2025 Approximately $1.49 per share Approximately $935,865 We intend to use the net proceeds, to continue normal business operations related to our strategic pivotfocused on the Energy Base product and ongoing contracting activities. See “Use of Proceeds” on pageS-11 in our prospectus supplement dated July 11, 2025. “GWH” This prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectusdated November 17, 2022 also cover the resale of shares by YA II PN, Ltd. to the public. See “Plan ofDistribution” on page S-12 in our prospectus supplement dated July 11, 2025. WHERE YOU CAN FIND MORE INFORMATION We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are availableto the public over the Internet at the SEC’s website at www.sec.gov. Copies of certain information filed by us with the SEC are alsoavailable on our website at https: