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Founding chair Michael Niggli to leave ESS Tech (NYSE: GWH) board

Filing Impact
(Moderate)
Filing Sentiment
(Neutral)
Form Type
8-K

Rhea-AI Filing Summary

ESS Tech, Inc. reported that director and Founding Chairman Michael Niggli has notified the company he will resign from its Board of Directors, Audit Committee, and Nominating and Corporate Governance Committee, effective as of the 2026 annual meeting of stockholders on May 29, 2026.

The company stated that Mr. Niggli’s resignation is not due to any disagreement regarding operations, policies, or practices. ESS Tech expressed gratitude for his leadership as Founding Chairman and his years of service and contributions to the company.

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Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers Governance
Key personnel changes including departures, elections, or appointments of directors and executive officers.
Annual meeting date May 29, 2026 Effective date of Michael Niggli’s resignation
Par value $0.0001 per share Common stock par value
Warrant exercise price $172.50 per share Exercise price for each whole warrant
Emerging growth company regulatory
"Emerging growth company"
An emerging growth company is a recently public or smaller public firm that qualifies for temporary, lighter regulatory and disclosure rules to reduce the cost and effort of being public. For investors, it means the company may provide less historical financial detail and face fewer reporting requirements than larger firms, so it can grow more quickly but also carries higher uncertainty—like buying a promising early-stage product with fewer user reviews.
Audit Committee financial
"Board of Directors, Audit Committee and Nominating and Corporate Governance Committee"
A company's audit committee is a small group of board members who act like independent inspectors for the firm's finances, overseeing how financial reports are prepared, monitoring internal controls, and managing the relationship with external auditors. Investors care because a strong audit committee reduces the risk of accounting errors, fraud, or misleading statements, making financial statements more trustworthy and helping protect shareholder value.
Nominating and Corporate Governance Committee financial
"Board of Directors, Audit Committee and Nominating and Corporate Governance Committee"
A nominating and corporate governance committee is a group within a company's board of directors responsible for selecting and recommending individuals to serve as company leaders, such as directors or executives. They also develop and oversee policies to ensure the company is run fairly, ethically, and transparently. This committee matters to investors because it helps ensure the company is well-managed and guided by qualified, responsible leadership.
Founding Chairman other
"leadership on its board of directors as the Founding Chairman of the Company"
0001819438False00018194382026-04-102026-04-100001819438wk:CommonStock0.0001ParValuePerShareMember2026-04-102026-04-100001819438wk:WarrantsEachWholeWarrantExercisableForOneShareOfCommonStockAtAnExercisePriceOf11.50Member2026-04-102026-04-10

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, 2026
ESS TECH, INC.
(Exact Name of Registrant as Specified in Charter)
Delaware001-3952598-1550150
(State or other jurisdiction
of incorporation)
(Commission
File Number)
(I.R.S. Employer
Identification Number)
26440 SW Parkway Ave., Bldg. 83
Wilsonville, Oregon
 97070
(Address of principal executive offices) (Zip code)
(855) 423-9920
(Registrant’s telephone number, including area code)
Not Applicable
(Former name or former address, if changed since last report)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the Registrant under any of the following provisions:
Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))
Securities registered pursuant to Section 12(b) of the Act:
Title of each class
Trading
Symbol(s)
Name of each exchange
on which registered
Common Stock, $0.0001 par value per shareGWHThe New York Stock Exchange
Warrants, each whole warrant exercisable for one share of common stock at an exercise price of $172.50GWH.WThe New York Stock Exchange
Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).
Emerging growth company
If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐




Item 5.02    Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.
Resignation of Director
On April 10, 2026, Michael Niggli notified ESS Tech, Inc. (the “Company”) that he is resigning from the Company’s Board of Directors (the “Board”), Audit Committee and Nominating and Corporate Governance Committee, effective as of the date of the Company’s 2026 annual meeting of stockholders to be held on May 29, 2026.
The resignation of Mr. Niggli was not the result of any disagreement with the Company on any matter relating to its operations, policies, or practices.
The Company is grateful for Mr. Niggli’s leadership on its board of directors as the Founding Chairman of the Company and for his years of service and valuable contributions to the Company.



SIGNATURE
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, hereunto duly authorized.
Dated: April 15, 2026
ESS TECH, INC.
By:/s/ Kate Suhadolnik
Name:Kate Suhadolnik
Title:Chief Financial Officer

FAQ

What board change did ESS Tech (GWH) disclose in this 8-K?

ESS Tech disclosed that director and Founding Chairman Michael Niggli will resign from the Board, Audit Committee, and Nominating and Corporate Governance Committee, effective as of the 2026 annual meeting of stockholders scheduled for May 29, 2026.

When will Michael Niggli’s resignation from ESS Tech (GWH) become effective?

Michael Niggli’s resignation becomes effective as of ESS Tech’s 2026 annual meeting of stockholders, which is scheduled to be held on May 29, 2026. He will continue to serve on the Board and its committees until that meeting.

Did Michael Niggli cite any disagreement with ESS Tech (GWH) in his resignation?

No. ESS Tech stated that Michael Niggli’s resignation was not the result of any disagreement with the company on matters relating to its operations, policies, or practices. The company emphasized its appreciation for his leadership and contributions.

What positions did Michael Niggli hold at ESS Tech (GWH)?

Michael Niggli served on ESS Tech’s Board of Directors and was the company’s Founding Chairman. He also sat on the Audit Committee and the Nominating and Corporate Governance Committee, roles he will hold until the May 29, 2026 annual meeting.

Who signed the ESS Tech (GWH) 8-K announcing the board resignation?

The 8-K was signed on behalf of ESS Tech by Chief Financial Officer Kate Suhadolnik. Her signature indicates that she is the authorized officer submitting the report regarding Michael Niggli’s planned resignation from the board and its committees.

Filing Exhibits & Attachments

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