Company Update

Securities and Exchange Commission for the offer and sale of shares of its common stock, par value $0.001 per share, having an aggregate offering price of up to $87,650,000 (the “Shares”), pursuant to that certain At the Market Offering Agreement, dated April 29, 2025, by and between the Company and H.C. Wainwright & Co., LLC (the “Sales Agreement”). The Prospectus Supplement amends and supplements the information in the prospectus dated April 29, 2025 (the “Prior Prospectus”), as previously amended and supplemented by the prospectus supplements dated April 29, 2025 and September 2, 2025 (together with the Prior Prospectus, the “ATM Prospectus”), filed as a part of our registration statement on Form S-3 (File No. 333-286638). The Prospectus Supplement should be read in conjunction with the ATM Prospectus, and is qualified by reference thereto, except to the extent that the information therein amends or supersedes the information contained in the ATM Prospectus. The Prospectus Supplement is not complete without, and may only be delivered or utilized in connection with, the ATM Prospectus and any future amendments or supplements thereto. The Company has previously sold 13,680,483 shares of its common stock for aggregate gross proceeds of approximately $12.3 million under the Sales Agreement. A copy of the opinion of Brownstein Hyatt Farber Schreck, LLP relating to the validity of the Shares is attached as Exhibit 5.1 hereto.   Item 9.01. Financial Statements and Exhibits.   (d) Exhibits.   Exhibit No.   Description 5.1   Opinion of Brownstein Hyatt Farber Schreck, LLP 23.1   Consent of Brownstein Hyatt Farber Schreck, LLP (included in Exhibit 5.1) 104   Cover Page Interactive Date File (embedded with the Inline XBRL document).         SIGNATURES   Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.     SOLUNA HOLDINGS, INC.       Date: September 23, 2025 By: /s/ David C. Michaels     David C. Michaels     Chief Financial Officer     (principal financial officer)