Sec Form 4 Filing - Yorktown Energy Partners X, L.P. @ Solaris Energy Infrastructure, Inc. - 2024-12-16

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 Yorktown Energy Partners X, L.P. 2. Issuer Name and Ticker or Trading Symbol Solaris Energy Infrastructure, Inc. [ SEI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 410 PARK AVENUE, 20TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 12/16/2024 (Street) NEW YORK, NY10022 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 Class A Common Stock 12/16/2024 C( 1 ) 975,000 A $ 0 ( 1 ) 975,000 D Class A Common Stock 12/16/2024 S( 2 ) 975,000 D $ 24.0075 ( 2 ) 0 D Class B Common Stock ( 3 ) 12/16/2024 J( 1 ) 975,000 D $ 0 ( 1 ) 7,079,234 D

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 Solaris Energy Infrastructure, LLC Units ( 4 ) 12/16/2024 C 975,000 ( 4 ) ( 4 ) Class A Common Stock 975,000 ( 4 ) 7,079,234 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Yorktown Energy Partners X, L.P. 410 PARK AVENUE, 20TH FLOOR NEW YORK, NY10022 X Signatures By: Yorktown X Company LP, its general partner, By: Yorktown X Associates LLC, its general partner, By: /s/ Robert A. Signorino, Managing Member 12/18/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Pursuant to the Second Amended and Restated Limited Liability Company Agreement of Solaris Energy Infrastructure, LLC ("Solaris LLC"), dated as of May 11, 2017, included as Exhibit 10.4 to Solaris Energy Infrastructure, Inc.'s (the "Issuer") Annual Report on Form 10-K for the year ended December 31, 2023 (as amended, the "Solaris LLC Agreement"), the shares of the Issuer's Class B common stock reported herein were cancelled for no consideration on a one-for-one basis upon the redemption by Yorktown Energy Partners X, L.P., a Delaware limited partnership ("Yorktown X"), of units in Solaris LLC ("Solaris LLC Units") (together with a corresponding number of shares of the Issuer's Class B common stock, par value $0.00 per share ("Class B common stock")) for shares of the Issuer's Class A common stock, par value $0.01 per share ("Class A common stock") reported herein. ( 2 )As previously disclosed in the Issuer's prospectus supplement dated December 10, 2024, filed with the U.S. Securities and Exchange Commission on December 11, 2024, on December 11, 2024, the Issuer completed a public underwritten offering of shares of Class A common stock, par value $0.01 per share (the "Offering"). On December 16, 2024, in connection with the underwriters' exercise of their option to purchase additional shares of Class A common stock in the Offering, Yorktown X sold 975,000 shares of Class A common stock at a price to the public of $24.75 per share, or a net per share price of $24.0075 after deducting $0.7425 per share of underwriting discounts and commissions. ( 3 )Each share of Class B common stock has no economic rights but entitles the holder to one vote on all matters to be voted on by the stockholders generally. ( 4 )Subject to the terms of the Solaris LLC Agreement, the Solaris LLC Units (together with a corresponding number of shares of the Issuer's Class B common stock) are exchangeable from time to time for shares of the Issuer's Class A common stock.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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