Sec Form 4 Filing - NIGGLI MICHAEL R @ ESS Tech, Inc. - 2021-11-09

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person NIGGLI MICHAEL R 2. Issuer Name and Ticker or Trading Symbol ESS Tech, Inc. [ GWH] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O ESS TECH, INC., 26440 SW PARKWAY AVE., BLDG. 83 3. Date of Earliest Transaction (MM/DD/YY) 11/09/2021 (Street) WILSONVILLE, OR97070 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 11/09/2021 J( 1 )( 2 ) 65,752( 3 ) A $ 10 480,166 D Common Stock 11/09/2021 J( 1 )( 2 ) 31,140( 4 ) A $ 10 227,400 I See footnote( 5 ) Common Stock 11/09/2021 J( 1 )( 2 ) 11,670( 6 ) A $ 10 85,225 I See footnote( 7 ) Common Stock 11/09/2021 J( 1 )( 2 ) 11,670( 6 ) A $ 10 85,225 I See footnote( 8 ) Common Stock 11/09/2021 J( 1 )( 2 ) 11,670( 6 ) A $ 10 85,225 I See footnote( 9 ) Common Stock 11/09/2021 J( 1 )( 2 ) 11,670( 6 ) A $ 10 85,225 I See footnote( 10 ) Common Stock 490,480 I See footnote( 11 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other NIGGLI MICHAEL R C/O ESS TECH, INC. 26440 SW PARKWAY AVE., BLDG. 83 WILSONVILLE, OR97070 X Signatures /s/ Amir Moftakhar, by power of attorney 11/12/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )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 "Issuer"), the reporting person is entitled to receive additional shares of Issuer common stock, for no additional consideration, if the volume weighted average price of Issuer 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 Issuer 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 Issuer common stock over twenty trading days within any thirty trading day period is greater than or equal to $15.00. Each of these conditions was met as of November 9, 2021. ( 2 )Following the closing of the merger, the Issuer determined that aggregate Transaction Expenses (as defined in the Merger Agreement) were lower than had been estimated at the time of closing. Pursuant to the Merger Agreement, this lower amount of Transaction Expenses resulted in an Expense Shortfall (as defined therein), which increased the Adjusted Equity Value (as defined therein). ( 3 )Effective as of November 9, 2021, the reporting person was entitled to receive 65,228 shares of Issuer common stock pursuant to the Earnout Rights and 524 shares of Issuer common stock pursuant to the Expense Shortfall. ( 4 )Effective as of November 9, 2021, the reporting person was entitled to receive 30,891 shares of Issuer common stock pursuant to the Earnout Rights and 249 shares of Issuer common stock pursuant to the Expense Shortfall. ( 5 )The shares are held of record by the Michael R. Niggli Family Trust for which the reporting person serves as trustee. ( 6 )Effective as of November 9, 2021, the reporting person was entitled to receive 11,577 shares of Issuer common stock pursuant to the Earnout Rights and 93 shares of Issuer common stock pursuant to the Expense Shortfall. ( 7 )The shares are held of record by the Chloe D. Niggli Gift Trust for which the reporting person serves as trustee. ( 8 )The shares are held of record by the Ian M. Niggli 2021 Gift Trust for which the reporting person serves as trustee. ( 9 )The shares are held of record by the Lorelei A. Niggli 2021 Gift Trust for which the reporting person serves as trustee. ( 10 )The shares are held of record by the Michael R. Niggli Jr. 2021 Gift Trust for which the reporting person serves as trustee. ( 11 )The shares are held of record by the Linda Naviaux Niggli Trust for which the reporting person's spouse serves as trustee.

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