X0206 3 2021-10-08 0 0001819438 ESS Tech, Inc. GWH 0001377160 NIGGLI MICHAEL R C/O ESS TECH, INC. 26440 SW PARKWAY AVE., BLDG. 83 WILSONVILLE OR 97070 1 0 0 0 Common Stock 414414 D Common Stock 196260 I See footnote Common Stock 490480 I See footnote Common Stock 73555 I See footnote Common Stock 73555 I See footnote Common Stock 73555 I See footnote Common Stock 73555 I See footnote Stock Option (right to buy) 0.3061 2028-10-18 Common Stock 177785 D Restricted Stock Units 2026-04-08 Common Stock 30053 D Pursuant to an "earnout" provision of the Agreement and Plan of Merger, dated as of May 6, 2021 (the "Merger Agreement"), by and among ACON S2 Acquisition Corp, SCharge Merger Sub, Inc., and ESS Tech, Inc., the reporting person is entitled to receive additional shares of common stock, for no additional consideration, if the volume weighted average price of the common stock over twenty trading days within any thirty trading day period exceeds certain thresholds (the "Earnout Rights"). Of these Earnout Rights, one half will be issued if the volume weighted average price of the common stock over twenty trading days within any thirty trading day period is greater than or equal to $12.50, and one half will be issued if the volume weighted average price of the common stock over twenty trading days within any thirty trading day period is greater than or equal to $15.00. The shares are held of record by the Michael R. Niggli Family Trust for which the reporting person serves as trustee. The shares are held of record by the Linda Naviaux Niggli Trust for which the reporting person's spouse serves as trustee. The shares are held of record by the Chloe D. Niggli Gift Trust for which the reporting person serves as trustee. The shares are held of record by the Ian M. Niggli 2021 Gift Trust for which the reporting person serves as trustee. The shares are held of record by the Lorelei A. Niggli 2021 Gift Trust for which the reporting person serves as trustee. The shares are held of record by the Michael R. Niggli Jr. 2021 Gift Trust for which the reporting person serves as trustee. The shares subject to the option vest in 48 equal monthly installments beginning on August 20, 2018. Each restricted stock unit, or RSU, represents a contingent right to receive one share of common stock. The RSUs vest if the common stock exceeds the same thresholds as the Earnout Rights described in footnote (1). Exhibit 24 - Power of Attorney /s/ Amir Moftakhar, by power of attorney 2021-10-18