STWO / ACON S2 Acquisition Corp - Class A - تصريحات هيئة الأوراق المالية والبورصات، التقرير السنوي، بيان الوكيل

13,059 Shares of Common Stock

Filed Pursuant to Rule 424(b)(2) Registration No. 333-268138 Prospectus Supplement No. 7 (to Prospectus dated November 17, 2022 and Prospectus Supplement dated July 11, 2025) 13,059 Shares of Common Stock Pursuant to this prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectus dated November 17, 2022 (as supplemented from time to time, the “Prospectus”), we are

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 29, 2025 ESS TECH, INC. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 29, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

34,950 Shares of Common Stock

Filed Pursuant to Rule 424(b)(2) Registration No. 333-268138 Prospectus Supplement No. 6 (to Prospectus dated November 17, 2022 and Prospectus Supplement dated July 11, 2025) 34,950 Shares of Common Stock Pursuant to this prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectus dated November 17, 2022 (as supplemented from time to time, the “Prospectus”), we are

110,000 Shares of Common Stock

Filed Pursuant to Rule 424(b)(2) Registration No. 333-268138 Prospectus Supplement No. 5 (to Prospectus dated November 17, 2022 and Prospectus Supplement dated July 11, 2025) 110,000 Shares of Common Stock Pursuant to this prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectus dated November 17, 2022 (as supplemented from time to time, the “Prospectus”), we ar

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 12, 2025 ESS TECH, INC. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 12, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

125,000 Shares of Common Stock

Filed Pursuant to Rule 424(b)(2) Registration No. 333-268138 Prospectus Supplement No. 4 (to Prospectus dated November 17, 2022 and Prospectus Supplement dated July 11, 2025) 125,000 Shares of Common Stock Pursuant to this prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectus dated November 17, 2022 (as supplemented from time to time, the “Prospectus”), we ar

Kate Suhadolnik Offer Letter, dated

Exhibit 10.3 Offer Letter 26440 SW Parkway., Wilsonville OR 97070 T: 855-423-9920 We are pleased to offer you, Kate Suhadolnik the position of SEC Reporting Manager, with ESS Tech., Inc. (the “Company”) effective upon your signing of this letter, and the Employee Proprietary Information and Inventions Assignment Agreement (EPIIAA) explained below. •Your full-time, [X] exempt employment with the Co

ESS Tech, Inc. Announces Second Quarter 2025 Financial Results Secured up to $31 million in new capital, strengthening balance sheet and extending operational runway Proposal activity exceeding 1.1 GWh following Energy Base launch Strengthened our le

Exhibit 99.1 ESS Tech, Inc. Announces Second Quarter 2025 Financial Results Secured up to $31 million in new capital, strengthening balance sheet and extending operational runway Proposal activity exceeding 1.1 GWh following Energy Base launch Strengthened our leadership team to advance the company vision with the appointment of Jigish Trivedi as COO Operating cash burn reduced by ~80% in June com

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 14, 2025 ESS TECH, INC. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 14, 2025 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

dated July 10, 2025, by and between the

CERTAIN INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY [***], HAS BEEN OMITTED BECAUSE IT IS BOTH (I) NOT MATERIAL AND (II) IS THE TYPE THAT THE COMPANY TREATS AS PRIVATE OR CONFIDENTIAL.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001

orm of Warrant to P

Exhibit 4.8 THIS WARRANT AND THE UNDERLYING SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR UNDER THE SECURITIES LAWS OF ANY STATE. THESE SECURITIES MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED EXCEPT AS PERMITTED UNDER THE ACT AND APPLICABLE STATE SECURITIES LAWS IN ACCORDANCE WITH APPLICABLE REGISTRATION REQUIREMENTS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 1, 2025 ESS TECH, INC. (Ex

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 1, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

500,000 Shares of Common Stock

Filed Pursuant to Rule 424(b)(2) Registration No. 333-268138 Prospectus Supplement No. 3 (to Prospectus dated November 17, 2022 and Prospectus Supplement dated July 11, 2025) 500,000 Shares of Common Stock Pursuant to this prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectus dated November 17, 2022 (as supplemented from time to time, the “Prospectus”), we ar

500,000 Shares of Common Stock

Filed Pursuant to Rule 424(b)(2) Registration No. 333-268138 Prospectus Supplement No. 2 (to Prospectus dated November 17, 2022 and Prospectus Supplement dated July 11, 2025) 500,000 Shares of Common Stock Pursuant to this prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectus dated November 17, 2022 (as supplemented from time to time, the “Prospectus”), we ar

214,633 Shares of Common Stock

Filed Pursuant to Rule 424(b)(2) Registration No. 333-268138 Prospectus Supplement No. 1 (to Prospectus dated November 17, 2022 and Prospectus Supplement dated July 11, 2025) 214,633 Shares of Common Stock Pursuant to this prospectus supplement, the prospectus supplement dated July 11, 2025 and the base prospectus dated November 17, 2022 (as supplemented from time to time, the “Prospectus”), we ar

The date of this Supplement No. 1 is July 11, 2025.

Filed Pursuant to Rule 424(b)(3) Registration No. 333-268138 SUPPLEMENT NO. 1 TO PROSPECTUS SUPPLEMENT DATED MARCH 31, 2025 (To Prospectus dated November 17, 2022) This Supplement No. 1 to Prospectus Supplement (this “Supplement No. 1”) amends and supplements the information in the prospectus, dated November 17, 2022, (the “Prospectus”), and the prospectus supplement, dated March 31, 2025 (the “AT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): July 9, 2025 ESS TECH, INC. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): July 9, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I

ESS Announces $31M Insider-Led Funding Package to Continue Execution of Strategic Shift and Secures First Energy Base Order

Exhibit 99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE ESS Announces $31M Insider-Led Funding Package to Continue Execution of Strategic Shift and Secures First Energy Base Order Wilsonville, Ore.– July 11, 2025 - ESS Tech, Inc. (“ESS” or the “Company”) (NYSE:GWH), a leading manufacturer of iron flow long-duration energy storage (LDES) systems for commercial- and utility-scale applications, today announc

Standby Equity Purchase Agreement, dated July 9, 2025, by and between ESS Tech, Inc. and YA II PN, LTD.

Exhibit 10.1 Execution Version STANDBY EQUITY PURCHASE AGREEMENT THIS STANDBY EQUITY PURCHASE AGREEMENT (this “Agreement”) dated as of July 9, 2025, is made by and between YA II PN, LTD., a Cayman Islands exempt limited company (the “Investor”), and ESS TECH, INC., a company incorporated under the laws of the State of Delaware (the “Company”). The Investor and the Company may be referred to herein

Up to $6,643,395 Common Stock

As filed pursuant to Rule 424(b)(2) Registration No. 333-268138 PROSPECTUS SUPPLEMENT (To Prospectus dated November 17, 2022) Up to $6,643,395 Common Stock ESS Tech, Inc. (the “Company”) entered into a Standby Equity Purchase Agreement with YA II PN, LTD., a Cayman Islands exempt limited company (“Yorkville”), on July 9, 2025 (the “SEPA”). The Company shall have the right, but not the obligation,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): June 3, 2025 ESS TECH, INC. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): June 3, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM SD SPECIALIZED DISCLOSURE REPORT ESS Tech, Inc. (Exact name of the registrant as specified in its charter)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM SD SPECIALIZED DISCLOSURE REPORT ESS Tech, Inc. (Exact name of the registrant as specified in its charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I.R.S. Employer Identification No.) 26440 SW Parkway Ave., Bldg. 83 Wilsonville, Oregon 97070 (Address of princip

Conflict Minerals Report of ESS Tech, Inc. for the year ended December 31, 202

EXHIBIT 1.01 Conflict Minerals Report of ESS Tech, Inc. For the Year Ended December 31, 2024 Introduction This Conflict Minerals Report (this "Report) has been prepared by ESS Tech, Inc. (“ESS,” the “Company,” “we,” “us,” and “our”) in accordance with Rule 13p-1 under the Securities Exchange Act of 1934, as amended, and the requirements of Form SD (collectively, the “Rule”). All terms used but not

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 27, 2025 ESS TECH, INC. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 27, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I

ESS Tech, Inc. Announces First Quarter 2025 Financial Results In Contracting for 50 MWh Energy Base Award with Arizona based Utility Proposal Activity up to ~1.2 GWh and Growing following Energy Base Product Launch Energy Warehouse Startup Completed

Exhibit 99.1 ESS Tech, Inc. Announces First Quarter 2025 Financial Results In Contracting for 50 MWh Energy Base Award with Arizona based Utility Proposal Activity up to ~1.2 GWh and Growing following Energy Base Product Launch Energy Warehouse Startup Completed in the Second Quarter for California Irrigation District systems ESS’ Made in the USA batteries Well Positioned to Navigate Tariff Volati

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 15, 2025 ESS TECH, INC. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 15, 2025 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 00

Kelly Goodman Offer Letter

Exhibit 10.16 February 14, 2022 Dear Kelly, As discussed, we are extending to you an offer of employment as Vice President of Legal reporting Eric Dresselhuys with a tentative start date of March 14, 2022. Compensation: •Your annual salary will be $255,000, paid out on a bi-monthly basis of $10,625. •As a part of accepting this offer, you will be granted restricted stock units valued at $600,000.

Credit Agreement, dated November 1, 2024, by and between ESS Tech, Inc. and Export-Import Bank of the United States

Exhibit 10.14 CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THE EXHIBIT BECAUSE IT IS BOTH NOT MATERIAL AND IS THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. Execution Version CREDIT AGREEMENT dated as of November 1, 2024 among ESS TECH, INC. as Borrower and EXPORT-IMPORT BANK OF THE UNITED STATES EXIM Bank Transaction No. AP089503XX EXIM Bank Transaction No. AP089503XX Te

, 2025, by and between ESS Tech

Exhibit 10.11 SEPARATION AGREEMENT AND RELEASE This Separation Agreement and Release (“Agreement”) is made by and between Eric Dresselhuys (“Executive”) and ESS Tech, Inc. (the “Company”) (jointly referred to as the “Parties” or individually referred to as a “Party”). RECITALS WHEREAS, Executive was employed by the Company at-will; WHEREAS, Executive signed an April 1, 2021 Employment Agreement wi

Up to $13,504,438 Common Stock

Filed Pursuant to Rule 424(b)(5) Registration No. 333-268138 PROSPECTUS SUPPLEMENT (To Prospectus dated November 17, 2022) Up to $13,504,438 Common Stock We have entered into a Sales Agreement, dated March 31, 2025, (the “Sales Agreement”), with Robert W. Baird & Co. Incorporated relating to shares of our common stock, $0.0001 par value per share, offered by this prospectus supplement and the acco

Calculation of Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) ESS Tech, Inc. (Exact name of registrant as specified in its charter) Table 1 - Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered (1) Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $0.0001 par value

As filed with the Securities and Exchange Commission on March 31, 2025

As filed with the Securities and Exchange Commission on March 31, 2025 Registration No.

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): March 31, 2025 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

ESS Tech, Inc. Announces Fourth Quarter and Full Year 2024 Financial Results Completed Commissioning and Grid Interconnection of First Two Energy Centers Delivered Eight Energy Center Systems to Florida Utility Achieved Breakeven Profitability on Ene

Exhibit 99.1 ESS Tech, Inc. Announces Fourth Quarter and Full Year 2024 Financial Results Completed Commissioning and Grid Interconnection of First Two Energy Centers Delivered Eight Energy Center Systems to Florida Utility Achieved Breakeven Profitability on Energy Center Design at the end of Q4, Almost a Year Ahead of Schedule Announced Energy Base, a New Modular, Non-Containerized Gigawatt-Hour

Amended and Restated Outside Director Compensation Policy

Exhibit 10.8 ESS TECH, INC. OUTSIDE DIRECTOR COMPENSATION POLICY ESS Tech, Inc. (the “Company”) believes that providing cash and equity compensation to its members of the Board of Directors (the “Board,” and members of the Board, the “Directors”) represents an effective tool to attract, retain and reward Directors who are not employees of the Company (the “Outside Directors”). This Outside Directo

Exhibit 4.2

Exhibit 4.2 DESCRIPTION OF CAPITAL STOCK The following descriptions of the capital stock of ESS Tech, Inc. (“us,” “our,” “we,” “ESS” or the “Company”) and certain provisions of our certificate of incorporation (as amended, the “certificate of incorporation”) and amended and restated bylaws are summaries and are qualified by reference to the certificate of incorporation and the amended and restated

Sales Agreement, dated March 31, 2025, by and between ESS Tech, Inc. and Robert W. Baird & Co. Incorporated

Exhibit 1.1 CERTAIN OF THE EXHIBITS AND SCHEDULES TO THIS EXHIBIT HAVE BEEN OMITTED IN ACCORDANCE WITH REGULATION S-K ITEM 601(A)(5). ESS TECH, INC. Common Stock ($0.0001 par value per share) Sales Agreement March 31, 2025 Robert W. Baird & Co. Incorporated 777 East Wisconsin Avenue Milwaukee, Wisconsin 53202 Ladies and Gentlemen: ESS Tech, Inc., a Delaware Corporation (the “Company”), confirms it

Compensation Recovery Policy

ESS TECH, INC. COMPENSATION RECOVERY POLICY As adopted on November 1, 2023 ESS Tech, Inc. (the “Company”) is committed to strong corporate governance. As part of this commitment, the Company’s Board of Directors (the “Board”) has adopted this clawback policy called the Compensation Recovery Policy (the “Policy”). This Policy is intended to further the Company’s pay-for-performance philosophy and t

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 OR o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-395

List of Subsidiaries

Exhibit 21.1 LIST OF SUBSIDIARIES None.

ESS Tech, Inc. Insider Trading Policy

ESS TECH, INC. INSIDER TRADING POLICY (As amended on August 8, 2024) A.POLICY OVERVIEW ESS Tech, Inc. (together with any subsidiaries, collectively the “Company”) has adopted this Insider Trading Policy (the “Policy”) to help you comply with the federal and state securities laws and regulations that govern trading in securities and to help the Company minimize its own legal and reputational risk.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 31, 2025 ESS TECH, INC. (Ex

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 31, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 24, 2025 ESS TECH, INC. (Ex

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 24, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

-2-

ESS Tech, Inc. Receives NYSE Notification March 28, 2025 WILSONVILLE, Ore.-(BUSINESS WIRE)- ESS Tech, Inc. (ESS) (NYSE:GWH), a leading manufacturer of iron flow long-duration energy storage (LDES) systems for utility- and commercial- scale applications, today announced that on March 24, 2025, it received a notice (the “Notice”) from the New York Stock Exchange (the “NYSE”) that ESS is not in compl

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 13, 2025 ESS TECH, INC.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 13, 2025 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Numbe

ESS Announces Actions to Position the Company for the Future Kelly Goodman appointed interim CEO and Board Engages Financial Advisors

Exhibit 99.1 ESS Announces Actions to Position the Company for the Future Kelly Goodman appointed interim CEO and Board Engages Financial Advisors Wilsonville, Ore.– February 13, 2025 - ESS Tech, Inc. (ESS) (NYSE:GWH), a leading manufacturer of iron flow long-duration energy storage (LDES) systems for utility- and commercial- scale applications, today announced changes with the intent to take the

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file numbe

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): November 13, 2024 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Numbe

ESS Tech, Inc. Announces Third Quarter 2024 Financial Results Installed and Commissioned Second Energy Center

Exhibit 99.1 ESS Tech, Inc. Announces Third Quarter 2024 Financial Results Installed and Commissioned Second Energy Center WILSONVILLE, Ore. – November 13, 2024 – ESS Tech, Inc. (“ESS,” “ESS, Inc.” or the “Company”) (NYSE: GWH), a leading manufacturer of long-duration energy storage systems (LDES) for commercial and utility-scale applications, today announced financial results for its third quarte

Entry into a Material Definitive Agreement, Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 1, 2024 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number

ACON / Aclarion, Inc. / Evans Craig E - SC 13D/A Activist Investment

SC 13D/A 1 ess-schedule13daevanssong.htm SC 13D/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D UNDER THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 1)* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 26916J106 (CUSIP Number) Craig Evans Julia Song ESS Tech, Inc. 26440 SW Parkway Ave., Bldg. 83 Wils

Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K/A (Amendment No. 1) CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 23, 2024 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Com

Regulation FD Disclosure, Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Material Modification to Rights of Security Holders, Financial Statements and Exhibits, Other Events, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 23, 2024 ESS TECH, INC. (Exact name of registrant as specified in charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

ESS Tech, Inc. Announces Reverse Stock Split August 23, 2024

Exhibit 99.1 ESS Tech, Inc. Announces Reverse Stock Split August 23, 2024 WILSONVILLE, Ore. - ESS Tech, Inc. (“ESS,” “ESS Inc.”) (NYSE:GWH), a leading manufacturer of long-duration energy storage systems (LDES) for commercial and utility-scale applications, today announced that it will effect a 1-for-15 reverse stock split of ESS’ issued and outstanding common stock, par value $0.0001 per share. T

Certificate of Amendment to the Certificate of Incorporation

Exhibit 3.1 CERTIFICATE OF AMENDMENT OF CERTIFICATE OF INCORPORATION OF ESS TECH, INC. ESS Tech, Inc., a Delaware corporation (the “Company”), hereby certifies as follows: 1. The name of the Company is ESS Tech, Inc. and the Company was first formed on July 21, 2020, under the laws of the Cayman Islands, under the name “ACON S2 Acquisition Corp.” 2. The Company filed a certificate of domestication

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 14, 2024 ESS TECH, INC. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 14, 2024 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

ESS Tech, Inc. Announces Second Quarter 2024 Financial Results Finalizing Funding Agreement for up to $50 Million with Export-Import Bank of the United States Began Production of Second Energy Center for Portland General Electric Energy Warehouse Bec

Exhibit 99.1 ESS Tech, Inc. Announces Second Quarter 2024 Financial Results Finalizing Funding Agreement for up to $50 Million with Export-Import Bank of the United States Began Production of Second Energy Center for Portland General Electric Energy Warehouse Becomes First Operational Long-Duration Energy Storage at an Airport Exited Q2 with Cash and Short-Term Investments over $74 Million; Expect

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

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 State

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

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 Defin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

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 Defin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM SD SPECIALIZED DISCLOSURE REPORT ESS Tech, Inc. (Exact name of the registrant as specified in its charter)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM SD SPECIALIZED DISCLOSURE REPORT ESS Tech, Inc. (Exact name of the registrant as specified in its charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I.R.S. Employer Identification No.) 26440 SW Parkway Ave., Bldg. 83 Wilsonville, Oregon 97070 (Address of princip

Conflict Minerals Report of ESS Tech, Inc. for the year ended December 31, 2023, as required by Items 1.01 and 1.02 of this Form SD.

EXHIBIT 1.01 Conflict Minerals Report of ESS Tech, Inc. For the Year Ended December 31, 2023 Introduction ESS Tech, Inc. (“ESS,” the “Company,” “we,” “us,” and “our”), has prepared this Conflict Minerals Report (this “Report”) pursuant to Rule 13p-1 under the Securities Exchange Act of 1934, as amended, and the requirements of Form SD (collectively, the “Rule”). All terms used but not defined in t

Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 21, 2024 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 00

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 7, 2024 ESS TECH, INC. (Exact

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 7, 2024 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I.

ESS Tech, Inc. Announces First Quarter 2024 Financial Results Q1 Revenue of $2.7 Million Partnered with Sapele Power to Supply LDES in Africa Completed Testing of First Energy Center for Portland General Electric Ordered Second Power Module Automatio

Exhibit 99.1 ESS Tech, Inc. Announces First Quarter 2024 Financial Results Q1 Revenue of $2.7 Million Partnered with Sapele Power to Supply LDES in Africa Completed Testing of First Energy Center for Portland General Electric Ordered Second Power Module Automation Line with 40% Greater Production Capacity Exited Q1 with Cash and Short-Term Investments over $89 million; Expected to Carry ESS Well I

Your Vote Counts! *Please check the meeting materials for any special requirements for meeting attendance. Smartphone users Point your camera here and vote without entering a control number For complete information and to vote, visit www.ProxyVote.co

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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

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 x Filed by a party other than the Registrant o Check the appropriate box: o Preliminary Proxy Statement o Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) x Definitive Proxy State

Description of securities

Exhibit 4.2 DESCRIPTION OF SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 The following descriptions of the capital stock of ESS Tech, Inc. (“us,” “our,” “we,” “ESS” or the “Company”) and certain provisions of our certificate of incorporation (as amended by the certificate of amendment to the certificate of incorporation, the “certificate of incorporation”) and

Amended and Restated Outside Director Compensation Policy

ESS TECH, INC. OUTSIDE DIRECTOR COMPENSATION POLICY ESS Tech, Inc. (the “Company”) believes that providing cash and equity compensation to its members of the Board of Directors (the “Board,” and members of the Board, the “Directors”) represents an effective tool to attract, retain and reward Directors who are not employees of the Company (the “Outside Directors”). This Outside Director Compensatio

Executive Incentive Compensation Plan

ESS TECH, INC. EXECUTIVE INCENTIVE COMPENSATION PLAN 1.Purposes of the Plan. The Plan is intended to increase stockholder value and the success of the Company by motivating Employees to (i) perform to the best of their abilities and (ii) achieve the Company’s objectives. 2.Definitions. (a)“Actual Award” means as to any Performance Period, the actual award (if any) payable to a Participant for the

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023 OR o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-395

ESS Tech, Inc. Announces Fourth Quarter and Full Year 2023 Financial Results Lowered Q4 Adjusted EBITDA loss by More Than 50% year over year Exited 2023 with Cash and Short-Term Investments over $100 million; Expected to Carry ESS Well Into H1’25 Del

Exhibit 99.1 ESS Tech, Inc. Announces Fourth Quarter and Full Year 2023 Financial Results Lowered Q4 Adjusted EBITDA loss by More Than 50% year over year Exited 2023 with Cash and Short-Term Investments over $100 million; Expected to Carry ESS Well Into H1’25 Delivered First Energy Warehouses to Honeywell Energy Warehouse manufacturing cost lowered by 60% in 2023 Target 40% 2024 EW Cost Reduction

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): March 13, 2024 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing, Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): March 6, 2024 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (

ESS Tech, Inc. Receives Continued Listing Standard Notice From NYSE

ESS Tech, Inc. Receives Continued Listing Standard Notice From NYSE WILSONVILLE, OREGON – March 8, 2024 – ESS Tech, Inc. (“ESS,” “ESS, Inc.” or the “Company”) (NYSE:GWH), a leading manufacturer of long-duration energy storage systems (LDES) for commercial and utility-scale applications, today announced that on March 6, 2024, it received notice (the “Notice”) from the New York Stock Exchange (the “

STWO / ACON S2 Acquisition Corp - Class A / Cycle Capital Fund III, L.P. - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1)* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 26916J106 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule

JOINT FILING AGREEMENT

EX-99.1 2 tm246081d1ex99-1.htm EXHIBIT 99.1 EXHIBIT 99.1 CUSIP No. 26916J106 JOINT FILING AGREEMENT THIS JOINT FILING AGREEMENT is entered into as of February 14, 2024, by and among the parties signatories hereto. The undersigned hereby agree that the Statement on Schedule 13D with respect to the shares of Common Stock of ESS Tech, Inc. is, and any amendment thereafter signed by each of the unders

Calculation of Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) ESS Tech, Inc. (Exact name of registrant as specified in its charter) Table 1 - Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered (1) Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $0.0001 par value

As filed with the Securities and Exchange Commission on February 9, 2024

As filed with the Securities and Exchange Commission on February 9, 2024 Registration No.

STWO / ACON S2 Acquisition Corp - Class A / Pangaea Ventures Fund III, LP Passive Investment

SC 13G/A 1 formsc13ga.htm UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 3)* ESS Tech, Inc. (Name of Issuer) Common stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate bo

Up to 16,491,754 Shares of Common Stock Warrants to Purchase up to 17,677,348 Shares of Common Stock Up to 17,677,348 Shares of Common Stock Underlying Warrants

Filed Pursuant to Rule 424(b)(3) Registration No. 333-275552 PROSPECTUS Up to 16,491,754 Shares of Common Stock Warrants to Purchase up to 17,677,348 Shares of Common Stock Up to 17,677,348 Shares of Common Stock Underlying Warrants This prospectus relates to the resale from time to time by the selling securityholders described in this prospectus or their permitted transferees (the “Selling Securi

ESS Tech, Inc. 26440 SW Parkway Ave., Bldg. 83 Wilsonville, Or, 97070

ESS Tech, Inc. 26440 SW Parkway Ave., Bldg. 83 Wilsonville, Or, 97070 December 12, 2023 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporation Finance 100 F Street, N.E. Washington, D.C. 20549 Attention: Erin Donahue Jay Ingram Re: ESS Tech, Inc. Registration Statement on Form S-3 File No. 333-275552 Acceleration Request Requested Date: December 14, 2023 Requested Time: 4:30 p.m

December 7, 2023

Wilson Sonsini Goodrich & Rosati Professional Corporation 650 Page Mill Road Palo Alto, California 94304-1050 o: 650.

As filed with the Securities and Exchange Commission on December 7, 2023

As filed with the Securities and Exchange Commission on December 7, 2023 Registration No.

Investment Warrant, dated September 21, 2023

Execution Version THIS WARRANT AND THE UNDERLYING SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR UNDER THE SECURITIES LAWS OF ANY STATE.

Performance Warrant, dated September 21, 2023

Execution Version THIS WARRANT AND THE UNDERLYING SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR UNDER THE SECURITIES LAWS OF ANY STATE.

As filed with the Securities and Exchange Commission on November 14, 2023

As filed with the Securities and Exchange Commission on November 14, 2023 Registration No.

IP Warrant, dated September 21, 2023

Execution Version THIS WARRANT AND THE UNDERLYING SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR UNDER THE SECURITIES LAWS OF ANY STATE.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file numbe

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Table Form S-3 (Form Type) ESS TECH, INC. (Exact Name of Registrant as Specified in its Charter) Table 1 - Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price Per Security Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Fees to be Paid Equity Common Stock,

Common Stock and Warrant Purchase Agreement, dated September 21, 2023, by and between the Company and Honeywell ACS Ventures LLC

Execution Version COMMON STOCK AND WARRANT PURCHASE AGREEMENT This Common Stock and Warrant Purchase Agreement (this “Agreement”) is dated as of September 21, 2023, by and between ESS Tech, Inc.

Registration Rights Agreement, dated September 21, 2023, by and between the Company and Honeywell ACS Ventures LLC

Execution Version REGISTRATION RIGHTS AGREEMENT This Registration Rights Agreement (this “Agreement”) is made and entered into as of September 21, 2023 (the “Effective Date”) by and between ESS Tech, Inc.

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): November 7, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number

ESS Tech, Inc. Announces Third Quarter 2023 Financial Results Announced Strategic Partnership with Honeywell

Exhibit 99.1 ESS Tech, Inc. Announces Third Quarter 2023 Financial Results Announced Strategic Partnership with Honeywell WILSONVILLE, Ore. – November 7, 2023 – ESS Tech, Inc. (“ESS,” “ESS, Inc.” or the “Company”) (NYSE: GWH), a leading manufacturer of long-duration energy storage systems for commercial and utility-scale applications, today announced financial results for its third quarter ended S

STWO / ACON S2 Acquisition Corp - Class A / HONEYWELL INTERNATIONAL INC - SC 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 ESS Tech, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 26916J106 (CUSIP Number) September 21, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: ¨ Rule

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Unregistered Sales of Equity Securities, Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): September 25, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Numb

HONEYWELL AND ESS TECH, INC. COLLABORATE TO ACCELERATE COMMERCIAL DEPLOYMENT OF IRON FLOW BATTERY ENERGY STORAGE SYSTEMS

Media Contacts: Honeywell: Mike Hockey +1 (832) 285-4933 [email protected] ESS: Morgan Pitts +1 (503) 568-0755 [email protected] HONEYWELL AND ESS TECH, INC. COLLABORATE TO ACCELERATE COMMERCIAL DEPLOYMENT OF IRON FLOW BATTERY ENERGY STORAGE SYSTEMS CHARLOTTE, NC and WILSONVILLE, OR – September 25, 2023 - Honeywell (Nasdaq: HON) today announced a strategic collaboration with ESS Tech

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 28, 2023 ESS TECH, INC. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 28, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

Harry Quarls Joins ESS Board of Directors as Chairman Energy industry veteran to further accelerate growth

Harry Quarls Joins ESS Board of Directors as Chairman Energy industry veteran to further accelerate growth WILSONVILLE, Ore.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 8, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

ESS Tech, Inc. Announces Second Quarter 2023 Financial Results Record Revenue of $2.8 Million Delivered Energy Warehouses™ to Four New Customers Announces Partnership with LEAG

Exhibit 99.1 ESS Tech, Inc. Announces Second Quarter 2023 Financial Results Record Revenue of $2.8 Million Delivered Energy Warehouses™ to Four New Customers Announces Partnership with LEAG WILSONVILLE, Ore. – August 8, 2023 – ESS Tech, Inc. (“ESS,” “ESS, Inc.” or the “Company”) (NYSE: GWH), a leading manufacturer of long-duration energy storage systems for commercial and utility-scale application

STWO / ACON S2 Acquisition Corp - Class A / Evans Craig E - SC 13D Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D UNDER THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. )* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 26916J106 (CUSIP Number) Craig Evans Julia Song ESS Tech, Inc. 26440 SW Parkway Ave., Bldg. 83 Wilsonville, Oregon 97070 (855) 423-9920 (Name, Address

Joint Filing Agreement, dated July 13, 2023, by and between Craig Evans and Dr. Julia Song.

Exhibit 3 JOINT FILING AGREEMENT In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree to the joint filing on behalf of each of them of a statement on Schedule 13D (including amendments thereto) with respect to the common stock, par value $0.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM SD SPECIALIZED DISCLOSURE REPORT ESS Tech, Inc. (Exact name of the registrant as specified in its charter)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM SD SPECIALIZED DISCLOSURE REPORT ESS Tech, Inc. (Exact name of the registrant as specified in its charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I.R.S. Employer Identification No.) 26440 SW Parkway Ave., Bldg. 83 Wilsonville, Oregon 97070 (Address of princip

Conflict Minerals Report of ESS Tech, Inc. for the year ended December 31, 2022, as required by Items 1.01 and 1.02 of this Form SD.

EXHIBIT 1.01 Conflict Minerals Report of ESS Tech, Inc. For the Year Ended December 31, 2022 Introduction ESS Tech, Inc. (“ESS,” the “Company,” “we,” “us,” and “our”), has prepared this Conflict Minerals Report (this “Report”) pursuant to Rule 13p-1 under the Securities Exchange Act of 1934, as amended, and the requirements of Form SD (collectively, the “Rule”). All terms used but not defined in t

Certificate of Amendment to the Certificate of Incorporation

Exhibit 3.1 CERTIFICATE OF AMENDMENT TO THE CERTIFICATE OF INCORPORATION OF ESS TECH, INC. (Pursuant to Section 242 of the General Corporation Law of the State of Delaware) ESS Tech, Inc., a corporation organized and existing under the laws of the State of Delaware, DOES HEREBY CERTIFY: FIRST: That the name of the corporation is ESS Tech, Inc. (the “Corporation”) and that the Corporation was first

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 22, 2023 ESS TECH, INC. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 22, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 00

ESS Tech, Inc. Announces First Quarter 2023 Financial Results Announces Partnership with Coldwell Solar

Exhibit 99.1 ESS Tech, Inc. Announces First Quarter 2023 Financial Results Announces Partnership with Coldwell Solar WILSONVILLE, Ore. – May 9, 2023 – ESS Tech, Inc. (“ESS,” “ESS, Inc.” or the “Company”) (NYSE: GWH), a leading manufacturer of long-duration energy storage systems for commercial and utility-scale applications, today announced financial results for its first quarter of 2023 ended Mar

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 9, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

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 x Filed by a party other than the Registrant o Check the appropriate box: o Preliminary Proxy Statement o Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) o Definitive Proxy State

Letter from Ernst & Young LLP

May 3, 2023 Securities and Exchange Commission 100 F Street, N.E. Washington, DC 20549 Ladies and Gentlemen: Refer to our letter issued with Item 4.01 of Form 8-K dated 14 April 2023 of ESS Tech, Inc. /s/ Ernst & Young LLP

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

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 x Filed by a party other than the Registrant o Check the appropriate box: o Preliminary Proxy Statement o Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) o Definitive Proxy State

Financial Statements and Exhibits, Changes in Registrant's Certifying Accountant

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 3, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): April 10, 2023 ESS TECH, INC. (Ex

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): April 10, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

Letter from Ernst & Young LLP

April 14, 2023 Securities and Exchange Commission 100 F Street, N.E. Washington, DC 20549 Ladies and Gentlemen: We have read Item 4.01 of Form 8-K dated 14 April 2023, of ESS Tech, Inc. and are in agreement with the statements contained in the first, second, third, and fourth paragraph on page two therein. Regarding the registrant’s statement concerning the lack of internal control to prepare fina

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

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 x Filed by a party other than the Registrant o Check the appropriate box: o Preliminary Proxy Statement o Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) x Definitive Proxy State

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

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 x Filed by a party other than the Registrant o Check the appropriate box: o Preliminary Proxy Statement o Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) o Definitive Proxy State

STWO / ACON S2 Acquisition Corp - Class A / Cycle Capital Fund III, L.P. - SC 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 26916J106 (CUSIP Number) March 29, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursua

JOINT FILING AGREEMENT

EXHIBIT 99.1 CUSIP No. 26916J106 JOINT FILING AGREEMENT THIS JOINT FILING AGREEMENT is entered into as of March 29, 2023, by and among the parties signatories hereto. The undersigned hereby agree that the Statement on Schedule 13D with respect to the shares of Common Stock of ESS Tech, Inc. is, and any amendment thereafter signed by each of the undersigned shall be, filed on behalf of each undersi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

PRE 14A 1 a2022esstechinc-preliminar.htm PRE 14A 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 x Filed by a party other than the Registrant o Check the appropriate box: x Preliminary Proxy Statement o Confidential, for Use of the Commission Only (as permit

2021 Employee Stock Purchase Plan

ESS TECH, INC. 2021 EMPLOYEE STOCK PURCHASE PLAN 1.Purpose. The purpose of the Plan is to provide employees of the Company and its Designated Companies with an opportunity to purchase Shares through accumulated Contributions. The Company intends for the Plan to have two components: a component that is intended to qualify as an “employee stock purchase plan” under Section 423 of the Code (the “423

Description of securities

Exhibit 4.2 DESCRIPTION OF SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 The following descriptions of the capital stock of ESS Tech, Inc. (“us,” “our,” “we,” “ESS” or the “Company”) and certain provisions of our amended and restated certificate of incorporation and amended and restated bylaws are summaries and are qualified by reference to the amended and res

Calculation of Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) ESS Tech, Inc. (Exact name of registrant as specified in its charter) Table 1 – Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $0.0001 par value

As filed with the Securities and Exchange Commission on March 2, 2023

As filed with the Securities and Exchange Commission on March 2, 2023 Registration No.

Employment Agreement, dated November 1, 2022, by and between ESS Tech, Inc. and Anthony Rabb

26440 SW Parkway., Wilsonville OR 97070 Exhibit 10.14 T: 855-423-9920 www.essinc.com OFFER LETTER October 31, 2022 Anthony Rabb Dear Anthony, As discussed, we are extending to you an offer of employment as Chief Financial Officer, reporting to Eric Dresselhuys with a start date of November 1, 2022. Compensation: •Your annual salary will be $415,000, paid out on a bi-monthly basis of $17,291.67 •As

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2022 OR o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-395

2021 Equity Incentive Plan and form of award agreements thereunder

ESS TECH, INC. 2021 EQUITY INCENTIVE PLAN 1.Purposes of the Plan. The purposes of this Plan are: •to attract and retain the best available personnel for positions of substantial responsibility, •to provide additional incentive to Employees, Directors and Consultants, and •to promote the success of the Company’s business. The Plan permits the grant of Incentive Stock Options, Nonstatutory Stock Opt

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): March 1, 2023 ESS TECH, INC. (Exa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): March 1, 2023 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (

ESS Tech, Inc. Announces Fourth Quarter and Full Year 2022 Financial Results Record Unit Deliveries in Q4 Ended Full Year 2022 with Almost 800 MWhs of Annual Production Capacity

Exhibit 99.1 ESS Tech, Inc. Announces Fourth Quarter and Full Year 2022 Financial Results Record Unit Deliveries in Q4 Ended Full Year 2022 with Almost 800 MWhs of Annual Production Capacity WILSONVILLE, OREGON – March 1, 2023 – ESS Tech, Inc. (“ESS,” “ESS, Inc.” or the “Company”) (NYSE:GWH), a leading manufacturer of long-duration energy storage systems for commercial and utility-scale applicatio

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SC 13G/A 1 d426911dsc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 2)* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 26916J106 (CUSIP Number) December 31, 2022 (Date of Event Which Requires Filing of this Statement) Check the A

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SC 13G/A 1 d304574dsc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 2)* ESS Tech, Inc. (Name of Issuer) Common stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) February 2, 2023 (Date of Event Which Requires Filing of this Statement) Check the ap

STWO / ACON S2 Acquisition Corp. Class A / Pangaea Ventures Fund III, LP - SC 13G/A Passive Investment

SC 13G/A 1 d414413dsc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 2)* ESS Tech, Inc. (Name of Issuer) common stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) December 31, 2022 (Date of Event Which Requires Filing of this Statement) Check the a

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): November 25, 2022 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Numbe

130,044,756 Shares of Common Stock

424B3 1 esstech-424b3.htm 424B3 Filed Pursuant to Rule 424(b)(3) Registration No. 333-263316 Registration No. 333-260693 130,044,756 Shares of Common Stock This prospectus relates to the registration of common stock, par value $0.0001 per share (“Common Stock”), of ESS Tech, Inc. as described herein. This prospectus relates to the resale from time to time by the selling stockholders described in t

November 15, 2022

November 15, 2022 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporation Finance 100 F Street, N.E. Washington, D.C. 20549 Attention: Gregory Herbers Re: ESS Tech, Inc. Registration Statement on Form S-3 Filed November 3, 2022 File No. 333-268138 Acceleration Request Requested Date: November 17, 2022 Requested Time: 4:30 p.m. (Eastern Time) Ladies and Gentlemen: Pursuant to Rule

As filed with the Securities and Exchange Commission on November 3, 2022

As filed with the Securities and Exchange Commission on November 3, 2022 Registration No.

As filed with the Securities and Exchange Commission on November 3, 2022

As filed with the Securities and Exchange Commission on November 3, 2022 Registration No.

Amended and Restated Bylaws of ESS

AMENDED AND RESTATED BYLAWS OF ESS TECH, INC. (effective October 20, 2022) TABLE OF CONTENTS Page ARTICLE I - CORPORATE OFFICES 1 1.1 REGISTERED OFFICE 1 1.2 OTHER OFFICES 1 ARTICLE II - MEETINGS OF STOCKHOLDERS 1 2.1 PLACE OF MEETINGS 1 2.2 ANNUAL MEETING 1 2.3 SPECIAL MEETING 1 2.4 ADVANCE NOTICE PROCEDURES 2 2.5 NOTICE OF STOCKHOLDERS? MEETINGS 10 2.6 QUORUM 10 2.7 ADJOURNED MEETING; NOTICE 11

Form of Indenture

Exhibit 4.3 ESS TECH, INC. INDENTURE Dated as of , 20 [] Trustee TABLE OF CONTENTS Page ARTICLE I DEFINITIONS AND INCORPORATION BY REFERENCE 1 Section 1.1 Definitions 1 Section 1.2 Other Definitions 6 Section 1.3 Incorporation by Reference of Trust Indenture Act 6 Section 1.4 Rules of Construction 6 ARTICLE II THE SECURITIES 7 Section 2.1 Issuable in Series 7 Section 2.2 Establishment of Terms of

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): November 3, 2022 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number

ESS Tech, Inc. Announces Third Quarter 2022 Financial Results Appoints Anthony Rabb as CFO

Exhibit 99.1 ESS Tech, Inc. Announces Third Quarter 2022 Financial Results Appoints Anthony Rabb as CFO WILSONVILLE, Ore. ? November 3, 2022 ? ESS Tech, Inc. (?ESS,? ?ESS, Inc.? or the ?Company?) (NYSE:GWH), a leading manufacturer of long-duration iron flow batteries for commercial and utility-scale energy storage applications, today announced financial results for its third quarter of 2022 ended

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Table Form S-3 (Form Type) ESS TECH, INC. (Exact Name of Registrant as Specified in its Charter) Table 1 - Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1)(2) Proposed Maximum Offering Price Per Security(3)(4) Maximum Aggregate Offering Price(4) Fee Rate Amount of Registration Fee Equity Common Stock, par

Warrant to Purchase Stock, dated September 16, 2022, by and between the Company and Sacramento Municipal Utility District

Certain information has been omitted from this exhibit in places marked ?[***]? because it contains personally identifiable information omitted from this exhibit pursuant to Item 601(a)(6) under Regulation S-K.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file numbe

130,044,756 Shares of Common Stock

PROSPECTUS SUPPLEMENT NO. 4 Filed Pursuant to Rule 424(b)(3) (to prospectus dated March 17, 2022) Registration No. 333-263316 Registration No. 333-260693 130,044,756 Shares of Common Stock This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated March 17, 2022 (as supplemented from time to time, the ?Prospectus?), with the information con

Amended and Restated Bylaws of ESS Tech, Inc. dated October 20, 2022

AMENDED AND RESTATED BYLAWS OF ESS TECH, INC. (effective October 20, 2022) TABLE OF CONTENTS Page ARTICLE I - CORPORATE OFFICES 1 1.1 REGISTERED OFFICE 1 1.2 OTHER OFFICES 1 ARTICLE II - MEETINGS OF STOCKHOLDERS 1 2.1 PLACE OF MEETINGS 1 2.2 ANNUAL MEETING 1 2.3 SPECIAL MEETING 1 2.4 ADVANCE NOTICE PROCEDURES 2 2.5 NOTICE OF STOCKHOLDERS? MEETINGS 10 2.6 QUORUM 10 2.7 ADJOURNED MEETING; NOTICE 11

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): October 21, 2022 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 26, 2022 (August 24, 2022) ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commi

130,044,756 Shares of Common Stock

PROSPECTUS SUPPLEMENT NO. 3 Filed Pursuant to Rule 424(b)(3) (to prospectus dated March 17, 2022) Registration No. 333-263316 Registration No. 333-260693 130,044,756 Shares of Common Stock This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated March 17, 2022 (as supplemented from time to time, the ?Prospectus?), with the information con

130,044,756 Shares of Common Stock

424B3 1 a2022q2esstechincformx424b3.htm 424B3 PROSPECTUS SUPPLEMENT NO. 2 Filed Pursuant to Rule 424(b)(3) (to prospectus dated March 17, 2022) Registration No. 333-263316 Registration No. 333-260693 130,044,756 Shares of Common Stock This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated March 17, 2022 (as supplemented from time to tim

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001

ESS Inc. Announces Second Quarter 2022 Financial Results Achieved Revenue Recognition on Energy WarehousesTM Announces Partnership with Energy Storage Industries Asia Pacific Announces Energy Center Deal with Tampa Electric Company

Exhibit 99.1 ESS Inc. Announces Second Quarter 2022 Financial Results Achieved Revenue Recognition on Energy WarehousesTM Announces Partnership with Energy Storage Industries Asia Pacific Announces Energy Center Deal with Tampa Electric Company WILSONVILLE, OREGON ? August 11, 2022 ? ESS Tech, Inc. (?ESS,? ?ESS, Inc.? or the ?Company?) (NYSE:GWH), a leading manufacturer of long-duration iron flow

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 11, 2022 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

130,044,756 Shares of Common Stock

PROSPECTUS SUPPLEMENT NO. 1 Filed Pursuant to Rule 424(b)(3) and Rule 424(b)(8) (to prospectus dated March 17, 2022) Registration No. 333-263316 Registration No. 333-260693 130,044,756 Shares of Common Stock This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated March 17, 2022 (as supplemented from time to time, the ?Prospectus?), with

Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): June 1, 2022 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 00

ESS Inc. Announces First Quarter 2022 Financial Results Expanded Company Operations to European Market

Exhibit 99.1 ESS Inc. Announces First Quarter 2022 Financial Results Expanded Company Operations to European Market WILSONVILLE, OREGON ? May 12, 2022 ? ESS Tech, Inc. (?ESS,? ?ESS, Inc.? or the ?Company?) (NYSE:GWH), a U.S. manufacturer of long-duration batteries for utility-scale and commercial energy storage applications, today announced financial results for its first quarter of 2022 ended Mar

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 12, 2022 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number) (I

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

DEF 14A 1 a2022esstechincproxya.htm DEF 14A 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 x Filed by a party other than the Registrant o Check the appropriate box: o Preliminary Proxy Statement o Confidential, for Use of the Commission Only (as permitted b

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): March 30, 2022 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

130,044,756 Shares of Common Stock

Table of Contents Filed Pursuant to Rule 424(b)(3) Registration No. 333-263316 Registration No. 333-260693 130,044,756 Shares of Common Stock This prospectus relates to the registration of common stock, par value $0.0001 per share (?Common Stock?), of ESS Tech, Inc. as described herein. This prospectus relates to the resale from time to time by the selling stockholders described in this prospectus

March 14, 2022

CORRESP 1 filename1.htm March 14, 2022 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporation Finance, Office of Manufacturing 100 F Street, N.E. Washington, D.C. 20549-3720 Attn: Gregory Herbers Re: ESS Tech, Inc. Registration Statement on Form S-1 (File No. 333-263316) Acceleration Request Requested Date: March 16, 2021 Requested Time: 4:30 P.M. Eastern Time Ladies and Gentlem

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2021 OR o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-395

As filed with the Securities and Exchange Commission on March 4, 2022

As filed with the Securities and Exchange Commission on March 4, 2022 Registration No.

Filing Fee Table (filed herewith).

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) ESS Tech, Inc. (Exact name of registrant as specified in its charter) Table 1 ? Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $0.0001 par value

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables FORM S-1 (Form Type) ESS TECH, INC. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered (1)(2) Proposed Maximum Offering Price Per Unit (3) Maximum Aggregate Offering Price Fee Rate Amount of Registration F

As filed with the Securities and Exchange Commission on March 4, 2022

As filed with the Securities and Exchange Commission on March 4, 2022 Registration No.

ESS Inc. Announces Fourth Quarter and Full Year 2021 Financial Results First Gen2 Energy Warehouse Shipped to Customer Has Been Fully Accepted and is Operational

Exhibit 99.1 ESS Inc. Announces Fourth Quarter and Full Year 2021 Financial Results First Gen2 Energy Warehouse Shipped to Customer Has Been Fully Accepted and is Operational WILSONVILLE, OREGON ? February 24, 2022 ? ESS Tech, Inc. (?ESS,? ?ESS, Inc.? or the ?Company?) (NYSE:GWH), a U.S. manufacturer of long-duration batteries for utility-scale and commercial energy storage applications, today ann

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): February 24, 2022 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Numbe

ESS Inc. Appoints Claudia Gast to its Board of Directors Private equity and financial expert to help guide company growth; venture investor Shirley Speakman steps down

Exhibit 99.1 FOR IMMEDIATE RELEASE ESS Inc. Appoints Claudia Gast to its Board of Directors Private equity and financial expert to help guide company growth; venture investor Shirley Speakman steps down Wilsonville, OR ? February 17, 2022: ESS Tech, Inc. (?ESS? or the ?Company?) (NYSE:GWH), a U.S. manufacturer of long-duration batteries for utility-scale and commercial energy storage applications,

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): February 17, 2022 (February 14, 2022) ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (C

STWO / ACON S2 Acquisition Corp. Class A / ACON S2 Sponsor, L.L.C. - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 1)* ESS TECH, INC. (Name of Issuer) COMMON STOCK, $0.0001 PAR VALUE PER SHARE (Title of Class of Securities) 26916J106 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the Appropriate Box to Designate the Rule Pu

JOINT FILING AGREEMENT

EXHIBIT A JOINT FILING AGREEMENT This will confirm the agreement by and among the undersigned that the Schedule 13G filed with the Securities and Exchange Commission on or about the date hereof with respect to the beneficial ownership by the undersigned of the shares of Common Stock, $0.

STWO / ACON S2 Acquisition Corp. Class A / GLAZER CAPITAL, LLC Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 ESS Tech, Inc. formerly known as ACON S2 Acquisition Corp (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) G00748106 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate bo

STWO / ACON S2 Acquisition Corp. Class A / RP Investment Advisors LP - AMENDMENT NO. 1 TO SCHEDULE 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* ACON S2 Acquisition Corp. (Name of Issuer) Class A ordinary shares, $0.0001 par value (Title of Class of Securities) G00748106 (CUSIP Number) December 31, 2021 (Date of Event which Requires Filing of this Statement) Check the appropriate box to designate

STWO / ACON S2 Acquisition Corp. Class A / BASF Venture Capital GmbH - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* ESS Tech, Inc. (Name of Issuer) Common stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pu

JOINT FILING AGREEMENT February 11, 2022

EXHIBIT 99.1 JOINT FILING AGREEMENT February 11, 2022 Pursuant to and in accordance with the Securities Exchange Act of 1934, as amended (the ?Exchange Act?), and the rules and regulations thereunder, each party hereto hereby agrees to the joint filing, on behalf of each of them, of any filing required by such party under Section 13 or Section 16 of the Exchange Act or any rule or regulation there

STWO / ACON S2 Acquisition Corp. Class A / Weiss Asset Management LP Passive Investment

CUSIP NO. 26916J106 SCHEDULE 13G/ PAGE 1 OF 10 PAGES =============================================================================== UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No.1)* ESS TECH, INC. (FORMERLY KNOWN AS ACON S2 ACQUISITION CORP.) - (Name of Issuer) Common Stock, $0.0001 par value per shar

26440 SW Parkway., Wilsonville OR 97070

RW 1 d238534drw.htm RW 26440 SW Parkway., Wilsonville OR 97070 T: 855-423-9920 www.essinc.com February 8, 2022 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporation Finance 100 F Street, NE Washington, D.C. 20549 Re: ESS Tech, Inc. Request for Withdrawal of Registration Statement on Form S-1 Registration No. 333-261900 Ladies and Gentlemen: On December 27, 2021, ESS Tech, Inc.

STWO / ACON S2 Acquisition Corp. Class A / Pangaea Ventures Fund III, LP - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* ESS Tech, Inc. (Name of Issuer) common stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pu

As filed with the Securities and Exchange Commission on December 27, 2021 Registration No. 333- SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT Under The Securities Act of 1933 ESS TECH, INC. (Exact name of R

Table of Contents Table of Contents As filed with the Securities and Exchange Commission on December 27, 2021 Registration No.

125,952,180 Shares of Common Stock

424B3 1 d456442d424b3.htm 424B3 Table of Contents Filed Pursuant to Rule 424(b)(3) Registration No. 333-260693 125,952,180 Shares of Common Stock This prospectus relates to the registration of common stock, par value $0.0001 per share (“Common Stock”), of ESS Tech, Inc. as described herein. This prospectus relates to the resale from time to time by the selling stockholders named in this prospectus

As filed with the Securities and Exchange Commission on December 14, 2021

S-8 1 d420614ds8.htm S-8 Table of Contents As filed with the Securities and Exchange Commission on December 14, 2021 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-8 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 ESS TECH, INC. (Exact name of Registrant as specified in its charter) Delaware 98-1550150 (State or other jurisdiction of in

Letter from Marcum LLP

Exhibit 16.2 December 9, 2021 Securities and Exchange Commission 100 F Street, N.E. Washington, DC 20549 Commissioners: We have read the statements made by ESS Tech, Inc. (formerly ACON S2 Acquisition Corp.) regarding our Firm?s dismissal included on pages 81 and 82 of the Post-Effective Amendment No. 1 to Form S-1 dated December 9, 2021. We agree with the statements concerning our Firm?s dismissa

As filed with the Securities and Exchange Commission on December 9, 2021 Registration No. 333-260693 SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-1 REGISTRATION STATEMENT Under The Securities Act

Table of Contents Table of Contents As filed with the Securities and Exchange Commission on December 9, 2021 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q/A (Amendment No. 1) (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 O

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q/A (Amendment No. 1) (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q/A (Amendment No. 1) (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2021 OR

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q/A (Amendment No. 1) (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commis

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K/A

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K/A (Amendment No. 2) (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2020 ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to ESS Tech, Inc

125,952,180 Shares of Common Stock

PROSPECTUS SUPPLEMENT NO. 3 Filed Pursuant to Rule 424(b)(3) (to prospectus dated November 10, 2021) Registration No. 333-260693 125,952,180 Shares of Common Stock This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated November 10, 2021 (as supplemented from time to time, the ?Prospectus?), with the information contained in the Current

125,952,180 Shares of Common Stock

Filed Pursuant to Rule 424(b)(3) Registration No. 333-260693 PROSPECTUS SUPPLEMENT NO. 4 (to prospectus dated November 10, 2021) 125,952,180 Shares of Common Stock This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated November 10, 2021 (as supplemented from time to time, the ?Prospectus?), with the information contained in the Current

Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K/A AMENDMENT NO. 1 CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 November 22, 2021 (September 30, 2021) (Date of Report (date of earliest event reported) ESS TECH, INC. (Exact name of registrant as specified in its charter) Delaware 001-39525 98-1550150 (State or other jurisdicti

STWO / ACON S2 Acquisition Corp. Class A / Cycle Capital Fund III, L.P. - SCHEDULE 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D/A (Rule 13d-101) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO ? 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO ? 240.13d-2(a) (Amendment No. 1)* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 26916J106 (CUSIP Number) Cycle Capital Fund

STWO / ACON S2 Acquisition Corp. Class A / BREAKTHROUGH ENERGY INVESTMENTS LLC - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D/A (Rule 13d-101) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO ? 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO ? 240.13d-2(a) (Amendment No. 1)* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 26916J106 (CUSIP Number) Breakthrough Energy

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2021 OR ☐ TRANSITION R

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Numbe

ESS MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

Exhibit 99.2 ESS MANAGEMENT?S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS Capitalized terms used but not defined in this Exhibit 99.2 shall have the meanings ascribed to them in the Current Report on Form 8-K (the ?Form 8-K?) filed with the Securities and Exchange Commission (the ?SEC?) on October 15, 2021 and, if not defined in the Form 8-K, the proxy statement/prospe

JOINT FILING AGREEMENT

EXHIBIT 99.1 CUSIP No. 26916J106 JOINT FILING AGREEMENT THIS JOINT FILING AGREEMENT is entered into as of November 22, 2021, by and among the parties signatories hereto. The undersigned hereby agree that the Statement on Schedule 13D with respect to the shares of Common Stock of ESS Tech, Inc. is, and any amendment thereafter signed by each of the undersigned shall be, filed on behalf of each unde

Changes in Registrant's Certifying Accountant, Non-Reliance on Previously Issued Financial Statements or a Related Audit Report or Completed Interim Review, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): November 22, 2021 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Numbe

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

Exhibit 99.3 UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION Defined terms included below shall have the same meaning as terms defined and included elsewhere in the Company?s Current Report on Form 8-K filed with the Securities and Exchange Commission on October 15, 2021, as amended on November 22, 2021 and, if not defined in the Form 8-K, the proxy statement/prospectus (File No. 333-

Exhibit 3              Joint Filing Agreement.

EX-3 2 tm2132816d1ex3.htm EXHIBIT 3 EXHIBIT 3 JOINT FILING AGREEMENT THIS JOINT FILING AGREEMENT is entered into as of November 22, 2021, by and among the parties signatories hereto. The undersigned hereby agree that the Statement on Schedule 13D with respect to the shares of Common Stock of ESS Tech, Inc. is, and any amendment thereafter signed by each of the undersigned shall be, filed on behalf

- 1 -

Exhibit 99.1 ESS TECH SUBSIDIARY, INC. (formerly known as ESS Tech, Inc.). Unaudited Condensed Financial Statements as of and for the Three and Nine Months Ended September 30, 2021 and 2020 ESS TECH SUBSIDARY, INC. TABLE OF CONTENTS PAGE UNAUDITED CONDENSED FINANCIAL STATEMENTS: CONDENSED BALANCE SHEETS AS OF SEPTEMBER 30, 2021 AND DECEMBER 31, 2020 2 CONDENSED STATEMENTS OF OPERATIONS AND COMPREH

STWO / ACON S2 Acquisition Corp. Class A / SOFTBANK GROUP CORP - SC 13D/A Activist Investment

SC 13D/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D (Rule 13d-101) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(a) (Amendment No. 1)* ESS Tech, Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) John T. Gaffne

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 12b-25 NOTIFICATION OF LATE FILING (Check One) ☐ Form 10-K ☐ Form 20-F ☐ Form 11-K ☒ Form 10-Q ☐ Form 10-D ☐ Form N-SAR ☐ Form N-CSR For Period Ended: September 30, 2021 ☐ T

NT 10-Q 1 d251002dnt10q.htm NT 10-Q SEC FILE NUMBER 001-39525 CUSIP NUMBER 26916J106 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 12b-25 NOTIFICATION OF LATE FILING (Check One) ☐ Form 10-K ☐ Form 20-F ☐ Form 11-K ☒ Form 10-Q ☐ Form 10-D ☐ Form N-SAR ☐ Form N-CSR For Period Ended: September 30, 2021 ☐ Transition Report on Form 10-K ☐ Transition Report on Form 20-F ☐

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): November 15, 2021 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Numbe

ESS Inc. Announces Third Quarter 2021 Financial Results Product shipments and deployments remain on schedule

Exhibit 99.1 ESS Inc. Announces Third Quarter 2021 Financial Results Product shipments and deployments remain on schedule WILSONVILLE, OREGON ? November 15, 2021 ? ESS Tech, Inc. (NYSE:GWH) (?ESS? or ?ESS Inc.?), a U.S. manufacturer of long-duration batteries for commercial and utility-scale energy storage applications, today announced financial results for its third quarter of 2021 ended Septembe

125,952,180 Shares of Common Stock

PROSPECTUS SUPPLEMENT NO. 1 Filed Pursuant to Rule 424(b)(3) (to prospectus dated November 10, 2021) Registration No. 333-260693 125,952,180 Shares of Common Stock This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated November 10, 2021 (as supplemented from time to time, the ?Prospectus?), with the information contained in the Current

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): November 9, 2021 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number

125,952,180 Shares of Common Stock

Filed Pursuant to Rule 424(b)(3) Registration No. 333-260693 PROSPECTUS SUPPLEMENT NO. 2 (to prospectus dated November 10, 2021) 125,952,180 Shares of Common Stock This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated November 10, 2021 (as supplemented from time to time, the ?Prospectus?), with the information contained in the Current

125,952,180 Shares of Common Stock

424B3 1 d238244d424b3.htm 424B3 Table of Contents Filed Pursuant to Rule 424(b)(3) Registration No. 333-260693 125,952,180 Shares of Common Stock This prospectus relates to the registration of common stock, par value $0.0001 per share (“Common Stock”), of ESS Tech, Inc. as described herein. This prospectus relates to the resale from time to time by the selling stockholders named in this prospectus

November 8, 2021

November 8, 2021 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporation Finance, Office of Manufacturing 100 F Street, N.E. Washington, D.C. 20549-3720 Attn: Gregory Herbers Re: ESS Tech, Inc. Registration Statement on Form S-1 File No. 333-260693 Acceleration Request Requested Date: November 10, 2021 Requested Time: 4:30 P.M. Eastern Time Ladies and Gentlemen: Pursuant to Rule

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): October 28, 2021 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number

As filed with the Securities and Exchange Commission on November 2 , 2021 Registration No. 333- SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT Under The Securities Act of 1933 ESS TECH, INC. (Exact name of R

Table of Contents As filed with the Securities and Exchange Commission on November 2 , 2021 Registration No.

List of Subsidiaries

Exhibit 21.1 ESS Tech, Inc. List of Subsidiaries (as of October 8, 2021) Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization ESS Tech Subsidiary, Inc. Delaware

Financial Statements and Exhibits, Changes in Registrant's Certifying Accountant

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): October 22, 2021 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number

Letter from Marcum LLP

EX-16.1 2 d198598dex161.htm EX-16.1 Exhibit 16.1 October 28, 2021 Securities and Exchange Commission 100 F Street, N.E. Washington, DC 20549 Commissioners: We have read the statements made by ESS Tech, Inc. (f/k/a ACON S2 Acquisition Corp.) under Item 4.01 of its Form 8-K dated October 28, 2021. We agree with the statements concerning our Firm in such Form 8-K; we are not in a position to agree or

JOINT FILING AGREEMENT

Exhibit 5 JOINT FILING AGREEMENT The undersigned hereby agree that the foregoing statement on Schedule 13D is filed on behalf of each of the undersigned, and any amendments thereto executed by the undersigned shall be filed on behalf of each of the undersigned without the necessity of filing any additional joint filing agreement.

SOFI / SoFi Technologies, Inc. / SOFTBANK GROUP CORP - SC 13D Activist Investment

SC 13D UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D (Rule 13d-101) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(a) (Amendment No. )* ESS Tech, Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) John T. Gaffney G

JOINT FILING AGREEMENT

Exhibit 1 JOINT FILING AGREEMENT In accordance with Rule 13d-1(k) promulgated under the Securities Exchange Act of 1934, as amended, each of the undersigned individually acknowledges and agrees that the foregoing statement on Schedule 13G is filed on behalf of such person and that subsequent amendments to this statement on Schedule 13G may be filed on behalf of such person without the necessity of filing an additional joint filing agreement.

STWO / ACON S2 Acquisition Corp / Pangaea Ventures Fund III, LP - SC 13G Passive Investment

SC 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* ESS Tech, Inc. (Name of Issuer) common stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) October 8, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rul

STWO / ACON S2 Acquisition Corp / BASF Venture Capital GmbH - SC 13G Passive Investment

SC 13G 1 d146382dsc13g.htm SC 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* ESS Tech, Inc. (Name of Issuer) Common stock, par value $0.0001 per share (Title of Class of Securities) 26916J106 (CUSIP Number) October 8, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropria

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 20, 2021 ESS TECH, INC. (Exact name of registrant as specified in its charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation or organizat

ESS Inc. Welcomes Alexi Wellman to Board of Directors Will also serve as Chair of the ESS Board Audit Committee

EX-99.1 2 d246830dex991.htm EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE ESS Inc. Welcomes Alexi Wellman to Board of Directors Will also serve as Chair of the ESS Board Audit Committee Wilsonville, OR—October 20, 2021: ESS Tech, Inc. (NYSE:GWH) (“ESS” or “ESS Inc.”), a U.S. manufacturer of long-duration batteries for commercial and utility-scale energy storage applications, announces the appointment

JOINT FILING AGREEMENT

EXHIBIT 99.1 CUSIP No. 26916J106 JOINT FILING AGREEMENT THIS JOINT FILING AGREEMENT is entered into as of October 18, 2021, by and among the parties signatories hereto. The undersigned hereby agree that the Statement on Schedule 13D with respect to the shares of Common Stock of ESS Tech, Inc. is, and any amendment thereafter signed by each of the undersigned shall be, filed on behalf of each under

JOINT FILING AGREEMENT

EX-99.1 2 tm2130211d1ex99-1.htm EXHIBIT 99.1 EXHIBIT 99.1 CUSIP No. 26916J106 JOINT FILING AGREEMENT THIS JOINT FILING AGREEMENT is entered into as of October 18, 2021, by and among the parties signatories hereto. The undersigned hereby agree that the Statement on Schedule 13D with respect to the shares of Common Stock of ESS Tech, Inc. is, and any amendment thereafter signed by each of the unders

STWO / ACON S2 Acquisition Corp / Cycle Capital Fund III, L.P. - SCHEDULE 13D Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D (Rule 13d-101) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO ? 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO ? 240.13d-2(a) (Amendment No. )* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 26916J106 (CUSIP Number) Cycle Capital Fund III

STWO / ACON S2 Acquisition Corp / BREAKTHROUGH ENERGY INVESTMENTS LLC - SCHEDULE 13D Activist Investment

SC 13D 1 tm2130211d2sc13d.htm SCHEDULE 13D UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D (Rule 13d-101) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2(a) (Amendment No. )* ESS Tech, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 2691

Assignment, Assumption and Amendment Agreement to the Warrant Agreement, dated October 8, 2021, by and among ESS, STWO, Continental Stock Transfer & Trust Company, Computershare Trust Company, N.A. and Computershare, Inc.

Exhibit 4.2 ASSIGNMENT, ASSUMPTION AND AMENDMENT AGREEMENT THIS ASSIGNMENT, ASSUMPTION AND AMENDMENT AGREEMENT (the ?Agreement?) is entered into and effective as of October 8, 2021 by and among ACON S2 Acquisition Corp., a Cayman Islands exempted company (?STWO?) (to be renamed ?ESS Tech, Inc.? effective as of the Closing (as defined below), or ?New ESS?), ESS Tech, Inc., a Delaware corporation (?

Outside Director Compensation Policy

EX-10.12 7 d231955dex1012.htm EX-10.12 Exhibit 10.12 ESS TECH, INC. OUTSIDE DIRECTOR COMPENSATION POLICY ESS Tech, Inc. (the “Company”) believes that providing cash and equity compensation to its members of the Board of Directors (the “Board,” and members of the Board, the “Directors”) represents an effective tool to attract, retain and reward Directors who are not employees of the Company (the “O

Form of Indemnification Agreement

Exhibit 10.2 ESS TECH, INC. INDEMNIFICATION AGREEMENT This Indemnification Agreement (this ?Agreement?) is dated as of , 2021, and is between ESS Tech, Inc., a Delaware corporation (the ?Company?), and [insert name of indemnitee] (?Indemnitee?). RECITALS A. Indemnitee?s service to the Company substantially benefits the Company. B. Individuals are reluctant to serve as directors or officers of corp

Stockholders’ Agreement, dated as of May 6, 2021, by and among ESS, SBE and BEV

Exhibit 10.5 STOCKHOLDERS? AGREEMENT This Stockholders? Agreement (this ?Agreement?) is made as of May 6, 2021, by and among ESS Tech, Inc., a Delaware corporation (the ?Company?), SB Energy Global Holdings One Ltd., a United Kingdom Limited corporation (the ?SBE Stockholder?) and Breakthrough Energy Ventures, LLC, a Delaware limited liability company (the ?BEV Stockholder?) (collectively, togethe

Amended and Restated Bylaws of ESS

Exhibit 3.2 AMENDED AND RESTATED BYLAWS OF ESS TECH, INC. (effective October 8, 2021) TABLE OF CONTENTS Page ARTICLE I - CORPORATE OFFICES 1 1.1 REGISTERED OFFICE 1 1.2 OTHER OFFICES 1 ARTICLE II - MEETINGS OF STOCKHOLDERS 1 2.1 PLACE OF MEETINGS 1 2.2 ANNUAL MEETING 1 2.3 SPECIAL MEETING 1 2.4 ADVANCE NOTICE PROCEDURES 2 2.5 NOTICE OF STOCKHOLDERS? MEETINGS 9 2.6 QUORUM 9 2.7 ADJOURNED MEETING; N

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

EX-99.1 8 d231955dex991.htm EX-99.1 Exhibit 99.1 UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION Defined terms included below shall have the same meaning as terms defined and included elsewhere in this Current Report on Form 8-K and, if not defined in the Form 8-K, the Registration Statement on Form S-4/A (File No. 333-257232) (the “Registration Statement”). Unless the context otherwi

Amended and Restated Certification of Incorporation of ESS

Exhibit 3.1 Delaware Page 1 The First State I, JEFFREY W. BULLOCK, SECRETARY OF STATE OF THE STATE OF DELAWARE, DO HEREBY CERTIFY THE ATTACHED IS A TRUE AND CORRECT COPY OF THE CERTIFICATE OF DOMESTICATION OF ?ACON S2 ACQUISITION CORP.?, FILED IN THIS OFFICE THE EIGHTH DAY OF OCTOBER, A.D. 2021, AT 12:40 O`CLOCK P.M. Jeffrey W. Bullock, Secretary of State 6288483 8100D Authentication: 204363952 SR

Regulation FD Disclosure, Changes in Control of Registrant, Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Amendment to Registrant's Code of Ethics, or Waiver of a Provision of the Code of Ethics, Change in Shell Company Status, Entry into a Material Definitive Agreement, Material Modification to Rights of Security Holders, Unregistered Sales of Equity Securities, Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing, Financial Statements and Exhibits, Completion of Acquisition or Disposition of Assets

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): October 8, 2021 ESS TECH, INC. (Exact Name of Registrant as Specified in Charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation) (Commission File Number)

ESS Inc. and ACON S2 Acquisition Corp. Announce Closing of Business Combination Creates First Publicly Traded U.S. Long-duration Storage Company Begins Trading on the NYSE on October 11, 2021 Under the Ticker “GWH”

Exhibit 99.1 ESS Inc. and ACON S2 Acquisition Corp. Announce Closing of Business Combination Creates First Publicly Traded U.S. Long-duration Storage Company Begins Trading on the NYSE on October 11, 2021 Under the Ticker ?GWH? WILSONVILLE, Ore. & WASHINGTON, Oct. 11, 2021 (GLOBE NEWSWIRE) ? October 11, 2021 ? ESS Inc. (?ESS? or the ?Company?), a U.S. manufacturer of long-duration batteries for co

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 11, 2021 ESS TECH, INC. (Exact name of registrant as specified in its charter) Delaware 001-39525 98-1550150 (State or other jurisdiction of incorporation or organizat

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-A FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES PURSUANT TO SECTION 12(b) OR (g) OF THE SECURITIES EXCHANGE ACT OF 1934 ESS TECH, INC. (Exact name of Registrant as spe

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-A FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES PURSUANT TO SECTION 12(b) OR (g) OF THE SECURITIES EXCHANGE ACT OF 1934 ESS TECH, INC. (Exact name of Registrant as specified in its charter) Delaware 98-1550150 (State of incorporation or organization) (I.R.S. Employer Identification No.) 26440 SW Parkway Ave., Bldg.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 25 NOTIFICATION OF REMOVAL FROM LISTING AND/OR REGISTRATION UNDER SECTION 12(b) OF THE SECURITIES EXCHANGE ACT OF 1934. Commission File Number 001-39525 ACON S2 ACQUISITION

OMB APPROVAL OMB Number: 3235-0080 Expires: May 31, 2024 Estimated average burden hours per response 1.

Other Events, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 5, 2021 ACON S2 ACQUISITION CORP. (Exact name of registrant as specified in its charter) Cayman Islands 001-39525 98-1550150 (State or other jurisdiction of incorporat

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 1, 2021 ACON S2 ACQUISITION CORP. (Exact name of registrant as specified in its charter) Cayman Islands 001-39525 98-1550150 (State or other jurisdiction of incorporat

IRREVOCABLE PROXY AND POWER OF ATTORNEY

Exhibit 99.1 IRREVOCABLE PROXY AND POWER OF ATTORNEY This IRREVOCABLE PROXY AND POWER OF ATTORNEY (this ?Proxy Agreement?) is entered into as of September 30, 2021, by and among SB Energy Global Holdings One Ltd. (?SoftBank?), ACON S2 Acquisition Corp. (the ?Company?), ESS Tech, Inc. (?ESS?), and the Secretary of the Company (the ?Proxyholder?). Each of SoftBank, ESS, the Proxyholder and the Compa

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 1, 2021 ACON S2 A

425 1 d220644d425.htm 425 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 1, 2021 ACON S2 ACQUISITION CORP. (Exact name of registrant as specified in its charter) Cayman Islands 001-39525 98-1550150 (State or other

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 28, 2021 ACON S

425 1 d75735d425.htm 425 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 28, 2021 ACON S2 ACQUISITION CORP. (Exact name of registrant as specified in its charter) Cayman Islands 001-39525 98-1550150 (State or othe

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 28, 2021 ACON S2 ACQUISITION CORP. (Exact name of registrant as specified in its charter) Cayman Islands 001-39525 98-1550150 (State or other jurisdiction of incorpo