ESS Tech, Inc.

For the period ended Dec 31, 2025. Filed Mar 5, 2026.

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A company's yearly report to the SEC, with audited financial statements. It is the fullest account a company gives of its business, its finances and the risks it sees.

FY2025 · Filed Mar 5, 2026

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Contents

Item 15. Exhibits and Financial Statement Schedules

(a)Financial Statements and Schedules

The financial statements are set forth under“Part II - Item 8. Financial Statements and Supplementary Data” of this Annual Report on Form 10-K. Financial statement schedules have been omitted since they are either not required, not applicable, or the information is otherwise included.

(b) Exhibit Listing

Incorporated by Reference
Exhibit	Description	Form	File No.	Exhibit No.	Filing Date	Filed Herewith
2.1#	Merger Agreement, dated as of May 6, 2021, by and among ACON S2 Acquisition Corp., SCharge Merger Sub, Inc. and ESS Tech, Inc.	8-K	001-39525	2.1	May 7, 2021
3.1	Certificate of Incorporation of ESS	8-K	001-39525	3.1	October 15, 2021
3.2	Certificate of Amendment to the Certificate of Incorporation	8-K	001-39525	3.1	May 22, 2023
3.3	Certificate of Amendment to the Certificate of Incorporation	8-K	001-39525	3.1	August 23, 2024
3.4	Amended and Restated Bylaws of ESS	10-Q	001-39525	3.2	November 3, 2022
4.1	Warrant Agreement, dated September 16, 2020, by and between ACON S2 Acquisition Corp. and Continental Stock Transfer & Trust Company	S-4	333-257232	4.1	June 21, 2021
4.2	Description of Securities					X
4.3	Assignment, Assumption and Amendment Agreement to the Warrant Agreement, dated October 8, 2021	8-K	001-39525	4.2	October 15, 2021
4.4	Warrant to Purchase Stock, dated September 16, 2022, by and between the Company and Sacramento Municipal Utility District	10-Q	001-39525	4.3	November 3, 2022
4.5	Investment Warrant, dated September 21, 2023	10-Q	001-39525	4.4	November 14, 2023
4.6	IP Warrant, dated September 21, 2023	10-Q	001-39525	4.5	November 14, 2023
4.7	Performance Warrant, dated September 21, 2023	10-Q	001-39525	4.6	November 14, 2023
4.8	Registration Rights Agreement, dated September 21, 2023, by and between the Company and Honeywell ACS Ventures LLC	10-Q	001-39525	4.7	November 14, 2023
4.9	Form of Warrant to Purchase Common Stock dated July 10, 2025	10-Q	001-39525	4.8	August 14, 2025
4.10	Warrant to Purchase Common Stock, dated October 14, 2025	8-K	001-39525	4.1	October 14, 2025
10.1	Form of Registration Rights Agreement	8-K	001-39525	10.4	May 7, 2021
10.2	Form of Subscription Agreement	8-K	001-39525	10.1	May 7, 2021

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10.3	Stockholders’ Agreement, dated as of May 6, 2021, by and among ESS, SBE and BEV	8-K	001-39525	10.5	October 15, 2021
10.4#	Framework Agreement, dated as of March 31, 2021, by and between SBE US Holdings One, Inc. and ESS Tech, Inc.	S-4	333-257232	10.13	June 21, 2021
10.5	Office Lease Agreement, dated July 24, 2017, by and between ESS Tech, Inc. and Parkway Woods Business Park, LLC	S-4	333-257232	10.8	June 21, 2021
10.6†	2021 Equity Incentive Plan and form of award agreements thereunder	10-K	001-39525	10.9	March 2, 2023
10.7†	2021 Employee Stock Purchase Plan	10-K	001-39525	10.10	March 2, 2023
10.8†	Amended and Restated Outside Director Compensation Policy	10-K	001-39525	10.8	March 31, 2025
10.9†	Form of Indemnification Agreement	8-K	001-39525	10.2	October 15, 2021
10.10†	Employment Agreement, dated January 1, 2026, by and between ESS Tech, Inc. and Drew Buckley					X
10.11†	Separation and Release Agreement, dated February 13, 2025, by and between ESS Tech, Inc. and Eric Dresselhuys	10-K	001-39525	10.11	March 31, 2025
10.12	Common Stock and Warrant Purchase Agreement, dated September 21, 2023, by and between the Company and Honeywell ACS Ventures LLC	10-Q	001-39525	10.1	November 14, 2023
10.13†	Executive Incentive Compensation Plan	10-K	001-39525	10.17	March 13, 2024
10.14#	Credit Agreement, dated November 1, 2024, by and between ESS Tech, Inc. and Export-Import Bank of the United States	10-K	001-39525	10.15	March 31, 2025
10.15†	Kelly Goodman Offer Letter	10-K	001-39525	10.16	March 31, 2025
10.16†	Kate Suhadolnik Offer Letter, dated August 16, 2021	10-Q	001-39525	10.3	November 13, 2025
10.17†	Employment Agreement by and between the Company and Jigish Trivedi, dated August 12, 2025	10-Q	001-39525	10.4	November 13, 2025
10.18	Standby Equity Purchase Agreement, dated July 9, 2025, by and between ESS Tech, Inc. and YA II PN, LTD.	8-K	001-39525	10.1	July 11, 2025
10.19	Sale and Leaseback Agreement, dated July 10, 2025, by and between the Company and UOP LLC	10-Q	001-39525	10.2	August 14, 2025
10.20	Promissory Note, dated October 14, 2025	8-K	001-39525	10.1	October 14, 2025
10.21	Amendment No. 1 to Promissory Note, dated November 12, 2025	10-Q	001-39525	10.6	November 13, 2025

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10.22	Amendment No. 2 to Promissory Note, dated December 4, 2025	8-K	001-39525	10.1	December 5, 2025
10.23	Sales Agreement, dated November 13, 2025, by and between ESS Tech, Inc. and Yorkville Securities, LLC, BMO Capital Markets Corp., Canaccord Genuity LLC, Needham & Company, LLC and Stifel, Nicolaus & Company, Incorporated	8-K	001-39525	1.1	November 13, 2025
10.24	Amendment No. 3 to Promissory Note, dated February 27, 2026					X
19.1	ESS Tech, Inc. Insider Trading Policy	10-K	001-39525	19.1	March 31, 2025
21.1	List of Subsidiaries					X
23.1	Consent of KPMG LLP, Independent Registered Public Accounting Firm					X
24.1	Power of Attorney (contained in the signature page to this Annual Report on Form 10-K)					X
31.1	Certification of Principal Executive Officer pursuant to Rule 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as amended, with respect to the Company’s Annual Report on Form 10-K for the year ended December 31, 2025					X
31.2	Certification of Principal Financial Officer pursuant to Rule 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as amended, with respect to the Company’s Annual Report on Form 10-K for the year ended December 31, 2025					X
32.1*	Certification of Principal Executive Officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, with respect to the Company’s Annual Report on Form 10-K for the year ended December 31, 2025					X
32.2*	Certification of Principal Financial Officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, with respect to the Company’s Annual Report on Form 10-K for the year ended December 31, 2025					X
97.1	Compensation Recovery Policy	10-K	001-39525	97.1	March 31, 2025
101.INS	Inline XBRL Instance Document – the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document					X

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101.SCH	Inline XBRL Taxonomy Extension Schema Document	X
101.CAL	Inline XBRL Taxonomy Extension Calculation Linkbase Document	X
101.LAB	Inline XBRL Taxonomy Extension Label Linkbase Document	X
101.PRE	Inline XBRL Taxonomy Extension Presentation Linkbase Document	X
104	Cover Page Interactive Data File (formatted as inline XBRL with applicable taxonomy extension information contained in Exhibits 101)	X
†	Indicates management contract or compensatory plan or arrangement.
#	Portions of this exhibit have been omitted in accordance with Item 601 of Regulation S-K.
*	These exhibits are furnished with this Annual Report on Form 10-K and are not deemed filed with the Securities and Exchange Commission and are not incorporated by reference in any filing of ESS Tech, Inc. under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, whether made before or after the date hereof and irrespective of any general incorporation language contained in such filings.

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