The principal business address of each of the Reporting Persons is 250 W 55th Street, 31st Floor, New York, New York 10019.

Each of the Reporting Persons that are entities are organized under the laws of the State of Delaware. David Nanus is a citizen of the United States.

The information required by Item 4(a) is set forth in Rows 9 and 11 of the cover pages hereto for each Reporting Person and is incorporated herein by reference for each Reporting Person. The number of securities reported as beneficially owned herein relates to 19,025,277 share held by Lightning Power Holdings, LLC, of which 2,589,007 have been deposited in the Voting Trust as discussed below. The majority unit holder of Lightning Power Holdings, LLC is Fund III Lightning Holdings, LLC, whose majority unit holder is Granite Energy LLC, whose sole member is Granite Energy Holdings, LLC, whose sole member is LS Power Equity Partners III, L.P., whose general partner is LS Power Partners III, L.P., whose general partner is LS Power Fund III G.P., LLC. As a result of these relationships, these entities may be deemed to beneficially own the securities held by Lightning Power Holdings, LLC. The investment advisor of LS Power Equity Partners III, L.P. is LS Power Equity Advisors, LLC, whose President is David Nanus. As a result of the relationships described herein, each of LS Power Equity Advisors, LLC and Mr. Nanus may be deemed to share beneficial ownership of the 19,025,277 shares that may be deemed to be beneficially owned by LS Power Equity Partners III, L.P. Furthermore, LS Power Equity Advisors, LLC, is the investment advisor to LS Power Equity Partners IV L.P, which may be deemed to beneficially own the 5,224,723 shares held by the other Sellers. As a result LS Power Equity Advisors, LLC and Mr. Nanus may be deemed to beneficially own these 5,224,723 shares as well, for a total of 24,250,000 shares. Mr. Nanus disclaims beneficial ownership of all such shares. In connection with the closing, on January 30, 2026 of the transaction with NRG Energy, Inc. (the "Issuer") and certain of its subsidiaries, Lightning Power Holdings, LLC, Thunder Generation, LLC, and CCS Power Holdings, LLC ("Sellers"), and the Issuer entered into that certain Amended and Restated Voting Trust Agreement (the "Voting Trust Agreement") with Wilmington Savings Fund Society, FSB (the "Trustee"). Pursuant to the Voting Trust Agreement, Lighting Power Holdings, LLC and the other Sellers deposited 2,589,007 and 710,993 shares of Common Stock, respectively, in the Trust and granted to the Trustee, subject to certain exceptions, voting rights with respect to such shares. In addition, the Trustee is obligated to vote or cause to be voted the Common Stock in accordance with the written recommendations of (i) the board of directors of the Issuer or a duly organized committee thereof; or (ii) in the absence of a recommendation of the board of directors of the Issuer or a duly organized committee thereof, in accordance with the terms set forth in the Voting Trust Agreement. Therefore, the Trustee, pursuant to the Voting Trust Agreement, may be deemed to have the right to direct the voting of 2,589,007 of the reported shares of Common Stock beneficially owned by Lightning Power Holdings, LLC and indirectly held by Fund III Lightning Holdings, LLC, Granite Energy, LLC, Granite Energy Holdings, LLC, LS Power Equity Partners III, L.P., LS Power Partners III L.P., and LS Power Fund III G.P., LLC and 3,300,000 of the reported shares of Common Stock held indirectly by LS Power Equity Advisors, LLC and David Nanus. On January 30, 2026, the Sellers entered into a Joint Filing Agreement relating to the filing of this Schedule 13G, a copy of which is annexed hereto as Exhibit 99.1.

The information required by Item 4(b) is set forth in Rows 9 and 11 of the cover pages hereto for each Reporting Person and is incorporated herein by reference for each Reporting Person. The percent of class represented by the amount in Row (11) is based on 214,677,543 shares of Common Stock of the Issuer issued and outstanding as reported in the Issuer's Registration Statement on Form S-3 filed with the SEC on February 2, 2026.

The information required by Item 4(c)(i) is set forth in Row 5 of the cover pages hereto for each Reporting Person and is incorporated herein by reference for each Reporting Person.

The information required by Item 4(c)(ii) is set forth in Row 6 of the cover pages hereto for each Reporting Person and is incorporated herein by reference for each Reporting Person.

The information required by Item 4(c)(iii) is set forth in Row 7 of the cover pages hereto for each Reporting Person and is incorporated herein by reference for each Reporting Person.

The information required by Item 4(c)(iv) is set forth in Row 8 of the cover pages hereto for each Reporting Person and is incorporated herein by reference for each Reporting Person.