X0306 4 2022-03-01 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 2022-03-01 4 P 0 20000 5.0084 A 530235 D Common Stock 568312 I See footnote Common Stock 227407 I See footnote Common Stock 85228 I See footnote Common Stock 85228 I See footnote Common Stock 85228 I See footnote Common Stock 85228 I See footnote The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $4.93 to $5.07, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price. Reflects an increase of 16 shares pursuant to an adjustment of earnout shares reported on a Form 4 filed on November 12, 2021. Reflects an increase of 10 shares pursuant to an adjustment of earnout shares reported on a Form 4 filed on November 12, 2021. The shares are held of record by the Linda Naviaux Niggli Trust for which the reporting person's spouse serves as trustee. Reflects an increase of seven shares pursuant to an adjustment of earnout shares reported on a Form 4 filed on November 12, 2021. The shares are held of record by the Michael R. Niggli Family Trust for which the reporting person serves as trustee. Reflects an increase of three shares pursuant to an adjustment of earnout shares reported on a Form 4 filed on November 12, 2021 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. /s/ Amir Moftakhar, by power of attorney 2022-03-03