ESS Tech Inc美股招股说明书(2025-10-14版)

Up to $25,000,000 Common Stock This prospectus supplement amends and supplements the information in the prospectus supplement, dated July 11, 2025 andthe base prospectus dated November 17, 2022 (as supplemented from time to time, the “Prospectus”), filed with the Securities andExchange Commission as a part of our registration statement on Form S-3 (File No. 333-268138), relating to the offer and sale of upto $6,643,395 of shares of our common stock, $0.0001 par value per share, pursuant to the Standby Equity Purchase Agreemententered into by ESS Tech, Inc. (the “Company”) with YA II PN, LTD., a Cayman Islands exempt limited company (“Yorkville”), onJuly 9, 2025 (the “SEPA”). This prospectus supplement is registering the offer and sales of up to $25,000,000 of shares of ourcommon stock. This prospectus supplement should be read in conjunction with the Prospectus, and is qualified by reference thereto,except to the extent that the information herein amends or supersedes the information contained in the Prospectus. This prospectussupplement is not complete without, and may only be delivered or utilized in connection with, the Prospectus and any futureamendments or supplements thereto. The prospectus supplement, dated July 11, 2025, indicated that we were, at that time, subject toGeneral Instruction I.B.6. of Form S-3, which limited the amount that we were able to sell under the registration statement of whichthe prospectus forms a part. We are currently no longer subject to the offering limits imposed by General Instruction I.B.6. of Form S-3. If we become subject to the offering limits in General Instruction I.B.6. of Form S-3 in the future, we will file another prospectussupplement. As of the date of this prospectus supplement, we have sold an aggregate of 3,674,940 shares for gross proceeds of $6,294,377pursuant to the SEPA. As a result of such prior sales, as of the date of this prospectus supplement, shares having an aggregate offeringprice of up to $18,705,623 remain available for offer and sale under the SEPA through the Prospectus. Our shares of common stock are listed on the NYSE under the symbol “GWH.” On October 13, 2025, the closing sale price of ourcommon stock was $9.05 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 14, 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 and in the documents incorporatedby reference herein and therein. We and Yorkville take no responsibility for, and can provide no assurance as to the reliabilityof, any other information that others may give you. We are not making an offer of these securities in any state or jurisdictionwhere the offer is not permitted. You should assume that the information contained in or incorporated by reference in thisprospectus supplement or the Prospectus is accurate only as of their respective dates.