COUNTERPART AGREEMENT

Exhibit 10.26

COUNTERPART AGREEMENT

This COUNTERPART AGREEMENT, dated December 18, 2014 (this “Counterpart Agreement”) is delivered pursuant to that certain Credit and Guaranty Agreement, dated as of July 23, 2014 (as amended by that First Amendment to Credit and Guaranty Agreement dated as of August 25, 2014, and as further amended, supplemented or otherwise modified, the “Credit Agreement”; the terms defined therein and not otherwise defined herein being used herein as therein defined), by and among TERRAFORM POWER OPERATING, LLC (“Borrower”), TERRAFORM POWER, LLC, certain Subsidiaries of Borrower, as Guarantors, the Lenders party thereto from time to time, GOLDMAN SACHS BANK USA, as Administrative Agent and Collateral Agent, and the other Persons party thereto.

Section 1. Pursuant to Section 5.10 of the Credit Agreement, each of the undersigned hereby:

(a) agrees that this Counterpart Agreement may be attached to the Credit Agreement and that by the execution and delivery hereof, the undersigned becomes a Guarantor under the Credit Agreement and agrees to be bound by all of the terms thereof;

(b) represents and warrants that each of the representations and warranties set forth in the Credit Agreement and each other Credit Document and applicable to the undersigned is true and correct both before and after giving effect to this Counterpart Agreement, except to the extent that any such representation and warranty relates solely to any earlier date, in which case such representation and warranty is true and correct as of such earlier date; provided that, in each case, such materiality qualifier shall not be applicable to any representations and warranties that already are qualified or modified by materiality in the text thereof;

(c) certifies that no event has occurred or is continuing as of the date hereof, or will result from the transactions contemplated hereby on the date hereof, that would constitute an Event of Default or a Default;

(d) agrees to irrevocably and unconditionally guaranty the due and punctual payment in full of all Obligations when the same shall become due, whether at stated maturity, by required prepayment, declaration, acceleration, demand or otherwise (including amounts that would become due but for the operation of the automatic stay under Section 362(a) of the Bankruptcy Code, 11 U.S.C. § 362(a)) and in accordance with Section 7 of the Credit Agreement; and

(e) (i) agrees that this counterpart may be attached to the Pledge and Security Agreement, (ii) agrees that the undersigned will comply with all the terms and conditions of the Pledge and Security Agreement as if it were an original signatory thereto, (iii) grants to Collateral Agent a security interest in all of the undersigned’s right, title and interest in and to all “Collateral” (as such term is defined in the Pledge and Security Agreement) of the undersigned, in each case whether now or hereafter existing or in which the undersigned now has or hereafter acquires an interest and wherever the same may be located and (iv) delivers to Collateral Agent supplements to all schedules

attached to the Pledge and Security Agreement. All such Collateral shall be deemed to be part of the “Collateral” and hereafter subject to each of the terms and conditions of the Pledge and Security Agreement.

Section 2. Each of the undersigned agrees from time to time, upon request of Administrative Agent, to take such additional actions and to execute and deliver such additional documents and instruments as Administrative Agent may request to effect the transactions contemplated by, and to carry out the intent of, this Counterpart Agreement. Neither this Counterpart Agreement nor any term hereof may be changed, waived, discharged or terminated, except by an instrument in writing signed by the party (including, if applicable, any party required to evidence its consent to or acceptance of this Counterpart Agreement) against whom enforcement of such change, waiver, discharge or termination is sought. Any notice or other communication herein required or permitted to be given shall be given pursuant to Section 10.1 of the Credit Agreement, and all for purposes thereof, the notice address of each of the undersigned shall be the address as set forth on the signature page hereof. In case any provision in or obligation under this Counterpart Agreement shall be invalid, illegal or unenforceable in any jurisdiction, the validity, legality and enforceability of the remaining provisions or obligations, or of such provision or obligation in any other jurisdiction, shall not in any way be affected or impaired thereby.

THIS COUNTERPART AGREEMENT SHALL BE GOVERNED BY, AND SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO CONFLICT OF LAWS PRINCIPLES THEREOF THAT WOULD RESULT IN THE APPLICATION OF ANY LAW OTHER THAN THE LAW OF THE STATE OF NEW YORK.

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IN WITNESS WHEREOF, each of the undersigned has caused this Counterpart Agreement to be duly executed and delivered by its duly authorized officer as of the date above first written.