Exhibit 10.1

Engagement Letter Third Amendment

Piper Sandler Buyside Advisory Services

This third amendment (this “Third Amendment”), effective as of August 11, 2025, modifies the “Engagement Letter Second Amendment to Piper Sandler Buyside Advisory Services Agreement” dated March 8, 2024 (the “Second Amendment”). The Second Amendment, in turn, had previously amended and supplemented the original letter agreement between Piper Sandler and Sunergy Renewables LLC (“Sunergy”), dated January 18, 2022 (the “Engagement Letter”). The Engagement Letter, as previously amended by the Second Amendment and as now amended by this Third Amendment, is hereafter referred to as our “Agreement.”

Sunergy completed its merger with ESGEN Acquisition Corporation (“ESGEN”) on March 13, 2024, which merger resulted in ESGEN changing its name to Zeo Energy Corp. (“Zeo”). Zeo is the legal successor to ESGEN and as such, confirms that it is a party to the Second Amendment and the Engagement Letter, and has assumed all obligations of Sunergy as set forth in the Second Amendment and the Engagement Letter.

For the avoidance of doubt, except as expressly set forth below, all other provisions of the Second Amendment and the Engagement Letter (including Annex A thereto) shall continue in full force and effect. Piper Sandler acknowledges that once the Heliogen Buyside Advisory Fee is received by Piper Sandler, Zeo has no further fee obligation to Piper under the Agreement for any services related to any past or future Business Transaction. Nothing in this Third Amendment modifies the letter agreement between Piper Sandler and Zeo Energy Corp. executed October 8, 2024 regarding services related to a potential transaction involving SST Solar Holdings Inc. and/or NovaSource Power Opco’s C&I Business.

Zeo confirms that Piper Sandler has provided the buyside advisory services described in the Second Amendment to the full satisfaction of the Company.

1. Background. In February 2025, Piper Sandler introduced Zeo to the opportunity to acquire Heliogen, Inc. and its subsidiaries (together, “Heliogen”). Zeo subsequently entered into a formal .agreement to acquire and merge with Heliogen (the “Heliogen Acquisition”). This Third Amendment describes the remaining fees to be paid by Zeo to Piper Sandler for its services described in the Second Amendment, including any remaining fees related to or arising from the Heliogen Acquisition.

2. Heliogen Buyside Advisory Fee. Zeo has previously made partial payment to Piper Sandler for services provided under the Second Amendment; Zeo has paid Piper Sandler $500,000 in cash and issued to Piper Sandler 50,000 shares of Class A common stock. In consideration of the buy-side advisory services that Piper Sandler has performed (and the prior payments described in the preceding sentence), and subject to closing of the Heliogen Acquisition, Zeo agrees to further compensate Piper Sandler upon such closing by immediately (i) paying Piper Sandler $1.6875 million in cash, and (ii) issuing to Piper Sandler 677,711 shares of Zeo Class A common stock (the “Zeo Shares”) (the cash payment and issuance of Zeo Shares, collectively the “Heliogen Buyside Advisory Fee”). Piper Sandler agrees that 50% of the Zeo Shares shall be subject to lock-up and as such, Piper Sandler agrees that it will not sell 50% of the Zeo Shares until the date that is 45 days after the date of closing of the Heliogen Acquisition.

3. Further Agreements and Undertakings by Zeo.

4. Releases. Subject to (i) closing of the Heliogen Acquisition, (ii) receipt by Piper Sandler of the Heliogen Buyside Advisory Fee, together with receipt of any applicable Late Registration Fee(s), (iii) reimbursement of Piper Sandler’s outstanding expenses, and (iv) Zeo’s continuing compliance with all other obligations set forth in this Third Amendment, as well as the Second Amendment and the Engagement Letter (e.g., its indemnity, contribution and exculpation obligations under Annex A to the Engagement Letter), Piper Sandler agrees that all fee and expense reimbursement obligations (except such expense reimbursement obligations that may arise in the future and are covered by Annex A), Piper Sandler releases Zeo Energy Corp. and any of its subsidiaries (including Sunergy Renewables LLC), or agents from any claim related to or arising from such obligations. For the avoidance of doubt, this release does not extend to claims that arise as a result of Zeo’s breach of its compensation and expense reimbursement obligations under this Third Amendment.

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