Exhibit 99.3

GREENBACKER RENEWABLE ENERGY COMPANY LLC PO Box 43131 Providence, RI 02940-3131

EVERY VOTE IS IMPORTANT

SCAN The QR code or visit www.proxy-direct.com to vote your shares

LIVE AGENT Call                            with any questions. Specialists can assist with voting. Available Monday-Friday from 9 a.m. – 11 p.m. and Saturday 12 pm – 6 pm ET

CALL 1-800-337-3503 Follow the recorded instructions available 24 hours

MAIL Vote, Sign and Mail in the enclosed Business Reply Envelope

VOTE AT THE VIRTUAL MEETING Visit: meetnow.global/[                 ] On               at                , Eastern Time. To participate in the Virtual Meeting, enter the 14-digit control number from the shaded box on this card.

GREENBACKER RENEWABLE ENERGY COMPANY LLC ANNUAL MEETING OF SHAREHOLDERS TO BE HELD                 , 2026

THIS PROXY IS BEING SOLICITED BY THE BOARD OF DIRECTORS OF GREENBACKER RENEWABLE ENERGY COMPANY LLC. The undersigned shareholder(s) of Greenbacker Renewable Energy Company LLC, a Delaware limited liability company (“Greenbacker”), revoking previous proxies, hereby appoints                      or any one of them as true and lawful attorneys with power of substitution of each, to vote all shares of Greenbacker Renewable Energy Company LLC, that the undersigned is entitled to vote at the Annual Meeting of Shareholders to be held on              , 2026, at                 , Eastern time, and any adjournments or postponements thereof. The Meeting will be held virtually at the following Website: meetnow.global/[                  ], and shareholders will not be able to attend the Meeting in person. To participate in the Meeting enter the 14-digit control number from the shaded box on this card. The undersigned hereby acknowledges receipt of the Notice of Annual Meeting of Shareholders and of the accompanying Proxy Statement, the terms of each of which are incorporated by reference, and revokes any proxy heretofore given with respect to the Meeting.

In their discretion, the proxy holders named above are authorized to vote upon such other matters as may properly come before the meeting or any adjournment or postponement thereof.

Receipt of the Notice of the Annual Meeting of Shareholders and the accompanying Proxy Statement is hereby acknowledged. The votes entitled to be cast by the undersigned will be cast as indicated or FOR the proposals if no choice is indicated.

			VOTE VIA THE INTERNET: www.proxy-direct.com
			VOTE VIA THE TELEPHONE: 1-800-337-3503

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PLEASE SIGN, DATE ON THE REVERSE SIDE AND RETURN THE PROXY PROMPTLY USING THE ENCLOSED ENVELOPE.

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TO VOTE, MARK BLOCKS BELOW IN BLUE OR BLACK INK AS SHOWN IN THIS EXAMPLE:			X

A			Proposals			The Board of Directors unanimously recommends that you vote “FOR” the proposals as described in the Proxy Statement.

1.To elect the seven members of the Board of Directors of Greenbacker to hold office until the next annual meeting of shareholders or until their respective successors have been elected and qualified.

FOR ALL

WITHHOLD ALL

FOR ALL EXCEPT

01.    Robert Brennan

02.    David Sher

03.    Daniel de Boer

04.    Kathleen Cuocolo

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05.    Cynthia Curtis

06.    Robert Herriott

07.    David M. Kastin

INSTRUCTIONS: To withhold authority to vote for any individual nominee(s), mark the box “FOR ALL EXCEPT” and write the nominee’s number on the line provided.___________________________________________________________________________

FOR

AGAINST

ABSTAIN

2.To vote on a resolution to approve, on an advisory basis, Greenbacker’s executive compensation for the fiscal year ended December 31, 2025.

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FOR

AGAINST

ABSTAIN

3.To adopt the Agreement and Plan of Merger, dated as of July 21, 2026 (such agreement, as it may be amended from time to time, the “merger agreement”), by and among Greenbacker, MN8 Energy Holdings LLC (“MN8”), MN8 Energy, LLC (“MN8 Energy”) and Monarch Merger Sub, LLC (“Monarch Merger Sub”), pursuant to which, upon the terms and conditions of the merger agreement, Monarch Merger Sub will merge with and into Greenbacker (the “merger”), with Greenbacker surviving such merger as a direct, wholly-owned subsidiary of MN8 Energy and an indirect, wholly-owned subsidiary of MN8 (the “merger agreement proposal”).

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FOR

AGAINST

ABSTAIN

4.To approve on an advisory (non-binding) basis the compensation that may be paid or become payable to Greenbacker’s named executive officers that is based on or otherwise relates to the merger (the “merger-related compensation proposal”).

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FOR

AGAINST

ABSTAIN

5.To approve an Amendment to Greenbacker’s Fifth Amended and Restated Limited Liability Company Operating Agreement (the “Fifth Operating Agreement”) to amend the definition of “Roll-Up Transaction” set forth in Section 2.2 of the Fifth Operating Agreement (the “charter amendment proposal”).

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Important Notice Regarding the Availability of Proxy Materials for

Greenbacker Renewable Energy Company LLC,

Annual Meeting of Shareholders to be held on              , 2026.

The Notice of Annual Meeting, Proxy Statement and this proxy card are available at

https://www.proxy-direct.com/[             ]

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Authorized Signatures ─ This section must be completed for your vote to be counted. ─ Sign and Date Below

Note: Please sign exactly as your name(s) appear(s) on this proxy card, and date it. When shares are held jointly, each holder should sign. When signing as attorney, executor, guardian, administrator, trustee, officer of corporation or other entity or in another representative capacity, please give the full title under the signature.

Date (mm/dd/yyyy) ─ Please print date below

Signature 1 ─ Please keep signature within the box

Signature 2 ─ Please keep signature within the box

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