Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption “Experts” in the Registration Statement (Post-Effective Amendment No. 2 to Form S-1 on Form S-3 No. 333-263316 and Post-Effective Amendment No. 3 to Form S-1 on Form S-3 No. 333-260693) and related Prospectus of ESS Tech, Inc. for the registration of 130,044,756 shares of its common stock and to the incorporation by reference therein of our report dated March 3, 2022, with respect to the consolidated financial statements of ESS Tech, Inc., included in its Annual Report (Form 10-K) for the year ended December 31, 2021, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Portland, Oregon

November 3, 2022