11. Related Party Transactions

MeOH Power, Inc.

On December 18, 2013, MeOH Power, Inc. and the Company executed a Senior Demand Promissory Note (the Note) in the amount of $380 thousand to secure the intercompany amounts due to the Company from MeOH Power, Inc. upon the deconsolidation of MeOH Power, Inc. Interest accrues on the Note at the Prime Rate in effect on the first business day of the month, as published in the Wall Street Journal. At the Company’s option, all or part of the principal and interest due on this Note may be converted to shares of common stock of MeOH Power, Inc. at a rate of $0.07 per share. Interest began accruing on January 1, 2014. The Company recorded a full allowance against the Note. As of June 30, 2025 and December 31, 2024, $394 thousand and $385 thousand, respectively, of principal and interest are available to convert into shares of common stock of MeOH Power, Inc. Any adjustments to the allowance are recorded as miscellaneous expense during the period incurred.

Employee Receivables

Certain employees have a receivable due to the Company based on their stock-based awards, in which $128 thousand and $178 thousand was outstanding as of June 30, 2025 and December 31, 2024, respectively. The balance is currently presented as $31 thousand and $82 thousand, respectively within Prepaid expenses and other current assets as of June 30, 2025 and December 31, 2024, and $97 thousand and $96 thousand, respectively within Other assets on the condensed consolidated financial statements.

HEL Transactions

As discussed in the Company’s 2023 Annual Report and all agreements included as exhibits and defined within the 2023 Annual Report, on October 29, 2021, the Company completed the Soluna Callisto acquisition pursuant to the merger agreement (the “Merger Agreement”). The purpose of the transaction was for SCI to acquire substantially all of the assets (other than those assets physically located in Morocco) formerly held by Harmattan Energy, Ltd. (“HEL”), which assets consisted of SCI’s existing pipeline of certain cryptocurrency mining projects that HEL previously transferred to SCI, which was formed expressly for this purpose, and to provide SCI with the opportunity to directly employ or retain the services of four individuals whose services it had retained through HEL prior to the merger. As a result of the merger, each share of common stock of Soluna Callisto issued and outstanding immediately prior to the effective time of the merger, other than shares owned by the Company or any of our subsidiaries, was cancelled and converted into the right to receive a proportionate share of the Merger Consideration.

In connection with the Soluna Callisto acquisition, effective as of October 29, 2021, upon and subject to the terms and conditions of the Termination Agreement, on November 5, 2021: (1) the existing Operating and Management Agreements between HEL and SCI were terminated in all respects; and (2)(A) SCI paid HEL $725 thousand, (B) SHI issued to HEL the Termination Shares, and (C) HEL and SHI entered into an Amended and Restated Contingent Rights Agreement that, among other things, amended the existing Contingent Rights Agreement by and between HEL and SHI, dated January 13, 2020, to provide SHI the right to invest directly in certain cryptocurrency mining opportunities being pursued by HEL. SHI filed a registration statement with the SEC to register the resale of the Termination Shares on February 14, 2022.

Due to conditions being met within the Merger Agreement in relation to energization and retention of employees, the Company has advised SCI US Holdings LLC, a Delaware limited liability company, who is the sole Effective Time Holder (as defined in the Merger Agreement) of the right to receive the Merger Shares of the Company and that 19,800 Merger Shares were issued on May 26, 2023 and 39,600 Merger Shares were issued on October 10, 2023. SCI US Holdings LLC has consented to the issuance of such Merger Shares as required under the Merger Agreement and has directed the Company to issue such Merger Shares to its affiliate, HEL. Following the issuance of the 59,400 Merger Shares, a total of 59,400 Merger Shares remains available for possible issuance through October 29, 2026 pursuant to the terms of the Merger Agreement.

Several of HEL’s equity holders are affiliated with Brookstone Partners, the investment firm that previously held an equity interest in the Company through Brookstone Partners Acquisition XXIV, LLC. The Company’s two Brookstone-affiliated directors also serve as directors and, in one case, as an officer, of HEL and also have ownership interest in HEL. In light of these relationships, the various transactions by and between the Company and SCI, on the one hand, and HEL, on the other hand, were negotiated on behalf of the Company and SCI via an independent investment committee of the Board and separate legal representation. The transactions were subsequently unanimously approved by both the independent investment committee and the full Board.

Four of the Company’s directors have various affiliations with HEL.

Michael Toporek, the former Chief Executive Officer, and current Executive Chairman of the Board, owns (i) 90% of the equity of Soluna Technologies Investment I, LLC, which owns 57.9% of HEL and (ii) 100% of the equity of MJT Park Investors, Inc., which owns 3.1% of HEL, in each case, on a fully diluted basis. Mr. Toporek does not own directly, or indirectly, any equity interest in Tera Joule, LLC, which owns 9.2% of HEL; however, as a result of his 100% ownership of Brookstone IAC, Inc., which is the manager of Tera Joule, LLC, he has dispositive power over the equity interests that Tera Joule owns in HEL.

In addition, one of the Company’s directors, Matthew E. Lipman, serves as a director and is currently acting as President of HEL. Mr. Lipman does not directly own any equity interest in Tera Joule, LLC, which owns 9.2% of HEL; however, as a result of his position as a director and officer of Brookstone IAC, Inc., which is the manager of Tera Joule, LLC, he has dispositive power over the equity interests that Tera Joule owns in HEL. As a result, the approximate dollar value of the amount of Mr. Toporek’s and Mr. Lipman’s interest in the Company’s transactions with HEL for the year ended December 31, 2024 was $0 and $0, respectively.

John Belizaire, the Company’s Chief Executive Officer, and John Bottomley, who were elected to the Board upon the effective time of SCI’s acquisition of Soluna Callisto, serve as directors of HEL. In addition, Mr. Belizaire is the beneficial owner of 1,317,567 shares of common stock of HEL and 102,380 Class Seed Preferred shares, which are convertible into 86,763 shares of common stock of HEL. These interests give Mr. Belizaire an ownership of 10.54% in HEL. Mr. Belizaire also owns an interest in HEL indirectly through his 5.0139% interest in Tera Joule, LLC’s 965,945 Class Seed Preferred shares, which are convertible into 818,596 shares of common stock of HEL. Mr. Bottomley is the beneficial owner of 96,189, or approximately 0.72%, of the outstanding shares of common stock of HEL.

The Company owned approximately 1.79% of HEL, calculated on a converted fully diluted basis, as of June 30, 2025 and December 31, 2024. The Company’s equity investment of HEL was fully impaired in fiscal year 2023, as such the equity investment is valued at $0 for both June 30, 2025 and December 31, 2024. The Company may enter into additional transactions with HEL in the future.