Exhibit 4.13

Third Supplemental Indenture

THIRD SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of February 22, 2012 among Atlantic Oklahoma Wind, LLC, a Delaware limited liability company (the “New Guarantor”), Atlantic Power Corporation (or its successor), a British Columbia corporation (“Atlantic Power”), the Guarantors (the “Existing Guarantors”) under the Indenture referred to below, and Wilmington Trust, National Association, as trustee under the Indenture referred to below (the “Trustee”).

W I T N E S S E T H:

WHEREAS Atlantic Power has heretofore executed and delivered to the Trustee an Indenture (as such may be amended from time to time, the “Indenture”), dated as of November 4, 2011, providing for the issuance of its 9% Senior Notes due 2018 (the “Notes”);

WHEREAS under certain circumstances Atlantic Power is required (or permitted) to cause the New Guarantor to execute and deliver to the Trustee a supplemental indenture pursuant to which the New Guarantor shall unconditionally guarantee all of Atlantic Power’s obligations under the Notes pursuant to a Guarantee on the terms and conditions set forth herein; and

WHEREAS pursuant to Section 8.01 of the Indenture, the Trustee, Atlantic Power and the Existing Guarantors are authorized to execute and deliver this Supplemental Indenture.

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the New Guarantor, Atlantic Power, the Existing Guarantors and the Trustee mutually covenant and agree for the equal and ratable benefit of the Holders as follows:

1.Definitions.

(a)Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

(b)For all purposes of this Supplemental Indenture, except as otherwise herein expressly provided or unless the context otherwise requires:  (i) the terms and expressions used herein shall have the same meanings as corresponding terms and expressions used in the Indenture; and (ii) the words “herein,” “hereof” and “hereby” and other words of similar import used in this Supplemental Indenture refer to this Supplemental Indenture as a whole and not to any particular section hereof.

2.Agreement to Guarantee.  The New Guarantor hereby agrees, jointly and severally with all other Guarantors, to guarantee Atlantic Power’s obligations under the Notes and the Indenture on the terms and subject to the conditions set forth in Article 10 of the Indenture and to be bound by all other applicable provisions of the Indenture.  From and after the date hereof, the New Guarantor shall be a Guarantor for all purposes under the Indenture and the Notes.

3.Ratification of Indenture; Supplemental Indentures Part of Indenture.  Except as expressly amended hereby, the Indenture is in all respects ratified and confirmed and all the terms, conditions and provisions thereof shall remain in full force and effect.  This Supplemental Indenture shall form a part of the Indenture for all purposes, and every Holder heretofore or hereafter authenticated and delivered shall be bound hereby.

4.Governing Law.  THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, AS APPLIED TO CONTRACTS MADE AND PERFORMED WITHIN THE STATE OF NEW YORK (INCLUDING, WITHOUT LIMITATION, SECTION 5-1401 OF THE NEW YORK GENERAL OBLIGATIONS LAW OR ANY SUCCESSOR STATUTE).  EACH OF THE PARTIES HERETO AGREES TO SUBMIT TO

THE JURISDICTION OF THE COURTS OF THE STATE OF NEW YORK IN ANY ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO THIS SUPPLEMENTAL INDENTURE.

5.Trustee Makes No Representation.  The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which are made solely by Atlantic Power.

6.Multiple Counterparts.  The parties may sign multiple counterparts of this Supplemental Indenture.  Each signed counterpart shall be deemed an original, but all of them together represent one and the same agreement.

7.Headings.  The headings of this Supplemental Indenture have been inserted for convenience of reference only, are not to be considered a part hereof, and shall in no way modify or restrict any of the terms or provisions hereof.

IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed as of the date and year first above written.

NEW GUARANTOR:
ATLANTIC OKLAHOMA WIND, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

ATLANTIC POWER CORPORATION
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President and Chief Executive Officer
By:	/s/ Paul H. Rapisarda
	Name:	Paul H. Rapisarda
	Title:	Managing Director of Acquisitions and
		Asset Management
EXISTING GUARANTORS:
ATLANTIC AUBURNDALE, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC CADILLAC HOLDINGS, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC IDAHO WIND C, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC IDAHO WIND HOLDINGS, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

ATLANTIC PIEDMONT HOLDINGS, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC POWER GENERATION, INC.
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC POWER HOLDINGS, INC.
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC POWER SERVICES, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC POWER SERVICES CANADA GP
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

ATLANTIC POWER SERVICES CANADA LP
By:  ATLANTIC POWER SERVICES CANADA GP, INC., ITS GENERAL PARTNER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC POWER TRANSMISSION, INC.
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ATLANTIC RENEWABLES HOLDINGS, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
AUBURNDALE GP, LLC
By:  AUBURNDALE LP, LLC,
ITS SOLE MEMBER
By:  ATLANTIC AUBURNDALE, LLC,
ITS SOLE MEMBER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

AUBURNDALE LP, LLC
By:  ATLANTIC AUBURNDALE, LLC,
ITS SOLE MEMBER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
BADGER POWER ASSOCIATES, L.P.
By:  TETON POWER FUNDING, LLC,
ITS GENERAL PARTNER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
By:  BADGER POWER GENERATION I LLC,
ITS GENERAL PARTNER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
BADGER POWER GENERATION I LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
BADGER POWER GENERATION II LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

BAKER LAKE HYDRO LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
DADE INVESTMENT, L.P.
By:  NCP DADE POWER, LLC,
ITS GENERAL PARTNER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
EPSILON POWER FUNDING, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
HARBOR CAPITAL HOLDINGS, LLC
By:  ATLANTIC POWER HOLDINGS, INC.,
ITS SOLE MEMBER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
LAKE COGEN LTD.
By:  NCP LAKE POWER LLC
ITS GENERAL PARTNER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

LAKE INVESTMENT, L.P.
By:  NCP LAKE POWER, LLC
ITS GENERAL PARTNER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
NCP DADE POWER LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
NCP GEM LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
NCP LAKE POWER LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
NCP PASCO LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

OLYMPIA HYDRO LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ORLANDO POWER GENERATION I LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
ORLANDO POWER GENERATION II LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
PASCO COGEN, LTD.
By:  NCP DADE POWER LLC,
ITS GENERAL PARTNER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
TETON EAST COAST GENERATION LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

TETON NEW LAKE, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
TETON OPERATING SERVICES, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
TETON POWER FUNDING, LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
TETON SELKIRK LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President
CAPITAL POWER INCOME L.P.
By: CPI INCOME SERVICES LTD., ITS GENERAL PARTNER
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	Chief Executive Officer

[Signature Page to Third Supplemental Indenture]

CPI INCOME SERVICES LTD.
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	Chief Executive Officer
CPI POWER (US) GP
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	Chief Executive Officer
CURTIS PALMER LLC
By:	/s/ Barry E. Welch
	Name:	Barry E. Welch
	Title:	President

[Signature Page to Third Supplemental Indenture]

WILMINGTON TRUST, NATIONAL ASSOCIATION, as Trustee
By:	/s/ Joseph P. O’Donnell
	Name: Joseph P. O’Donnell
	Title: Vice President

[Signature Page to Third Supplemental Indenture]