THIS FIFTH SUPPLEMENTAL INDENTURE, dated as of November 1, 2008 (this “Supplemental Indenture”) is between SOUTHWESTERN PUBLIC SERVICE COMPANY, a New Mexico corporation (hereinafter called the “Issuer” or the “Company”), having its principal office at Tyler at Sixth Street, Amarillo, Texas 79101, and THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A. as successor to THE CHASE MANHATTAN BANK and THE BANK OF NEW YORK MELLON, as Trustee (hereinafter called the “Trustee”), having its office at 700 S. Flower Street, Suite 500, Los Angeles, California 90017.

Recitals of the Issuer

The Issuer and the Trustee have heretofore entered into an Indenture, dated as of February 1, 1999, a First Supplemental Indenture, dated as of March 1, 1999, a Second Supplemental Indenture dated as of October 1, 2001, a Third Supplemental Indenture dated as of October 1, 2003, a Fourth Supplemental Indenture dated as of October 1, 2006 (such Indenture, as supplemented by the First Supplemental Indenture, the Second Supplemental Indenture, the Third Supplemental Indenture, the Fourth Supplemental Indenture and this Supplemental Indenture, being hereinafter referred to as the “Indenture”), relating to the issuance at any time or from time to time of its Securities on terms to be specified at the time of issuance.  Pursuant to Section 7.08 of the Indenture, JPMorgan Chase Bank, N.A. succeeded The Chase Manhattan Bank as trustee under the Indenture and The Bank of New York subsequently succeeded JPMorgan Chase Bank, N.A. as trustee under the Indenture.  The Bank of New York Mellon (formerly known as The Bank of New York) subsequently resigned as trustee and The Bank of New York Mellon Trust Company, N.A. was appointed as successor trustee under the Indenture.  Terms used and not otherwise defined herein shall (unless the context otherwise clearly requires) have the respective meanings given to them in the Indenture.

The Indenture provides in Article Two thereof that, prior to the issuance of Securities of any series, the form of such Securities and the terms applicable to such series shall be established in, or pursuant to, the authority granted in a resolution of the Board of Directors (delivered to the Trustee in the form of a Bond Resolution) or established in one or more indentures supplemental thereto.

The Issuer desires by this Supplemental Indenture, among other things, to establish the form of the Securities of the Issuer of a Series, to be titled Series G Senior Notes, 8.75% due 2018 of the Issuer, and to establish the terms applicable to such series, pursuant to Sections 2.01 and 10.01 of the Indenture.  The Issuer has duly authorized the execution and delivery of this Supplemental Indenture.

Article Ten of the Indenture provides that the Issuer, when authorized by a resolution of its Board of Directors, and the Trustee may from time to time and at any time amend the Indenture without the consent of Securityholders for certain purposes enumerated in Section 10.01 thereof, including purposes set forth in subsection (4) of said Section 10.01.

The execution and delivery of this Supplemental Indenture by the parties hereto are in all respects authorized by the provisions of the Indenture.  All things necessary have been done to make this Supplemental Indenture a valid, legal and binding agreement of the Issuer, in accordance with its terms.

The Issuer has requested that the Trustee execute and deliver this Supplemental Indenture.

NOW, THEREFORE, THIS FIFTH SUPPLEMENTAL INDENTURE WITNESSETH:

For and in consideration of the premises, it is mutually covenanted and agreed, as follows:

ARTICLE I.

ESTABLISHMENT OF SERIES G NOTES, 8.75% DUE 2018

Section 1.01.  The title of the series of the Securities established by this Supplemental Indenture shall be Series G Senior Notes, 8.75% due 2018  of the Issuer (hereinafter called the “Series G Notes”).  The Series G Notes shall be issued in registered form substantially in the form set forth in Exhibit A hereto (which is hereby incorporated herein and made a part hereof), subject to changes in the form thereof made by the Issuer and acceptable to the Trustee.

Section 1.02.   The Series G Notes shall be limited to $250,000,000 aggregate principal amount except as provided in Section 1.06 of this Supplemental Indenture.

Section 1.03.  The Series G Notes may be issued in whole or in part as one or more Global Securities and The Depository Trust Company, or a nominee thereof, shall be the Depository for such Global Security or Global Securities.  The Depository for such Global Security or Global Securities representing Series G Notes may surrender one or more Global Securities representing Series G Notes in exchange in whole or in part for individual Series G Notes on such terms as are acceptable to the Issuer and such Depository and otherwise subject to the terms of Section 2.12 of the Indenture.

Section 1.04.  The Issuer hereby appoints, or confirms the appointment of, The Bank of New York Mellon Trust Company, N.A., as the Trustee, Transfer Agent and Paying Agent, subject to the provisions of the Indenture with respect to resignation, removal and succession, and subject, further, to the right of the Issuer to appoint additional agents (including Paying Agents).

Section 1.05.  The terms of the Series G Notes shall be as set forth in Exhibit A hereto, and shall include the payment and other terms reflected on the Series G Notes as actually executed, authenticated and delivered under the Indenture.

Section 1.06.  The Series G Notes may be reopened and additional Securities of Series G Notes may be issued in excess of the amount initially authenticated and delivered, provided that such additional Securities of Series G Notes will contain the same terms (including the stated maturity and interest rate) as the other Series G Notes.  Any such additional Securities of Series G Notes, together with the other Series G Notes, shall constitute a single series for purposes of the Indenture.

Section 1.07. (a) So long as any Series G Notes are outstanding, the Issuer will not issue, assume, guarantee (including any contingent obligation to purchase) or permit to exist any Debt

2

secured by any mortgage, security interest, pledge, or lien (herein referred to as a “Lien”) of or upon any Operating Property of the Issuer, whether owned at the date of the issuance of the Series G Notes or thereafter acquired, without in any such case effectively securing the outstanding Series G Notes (together with, if the Issuer shall so determine, any other Securities or Debt of or guaranteed by the Issuer ranking equally with, the Series G Notes) equally and ratably with such Debt; provided, however, that the foregoing restriction shall not apply to Debt secured by any of the following:

(1) Liens on any Operating Property existing at the time of acquisition thereof (which Liens may also extend to subsequent repairs, alterations and improvements to that Operating Property), provided that such Lien as a result of such acquisition is not extended to property owned by the Issuer immediately prior thereto and is not created in contemplation of such acquisition;

(2) Liens on Operating Property of a corporation existing at the time such corporation is merged into or consolidated with the Issuer, or at the time of a sale, lease, or other disposition of the properties of such corporation or a division thereof as an entirety or substantially as an entirety to the Issuer, provided that such Lien as a result of such merger, consolidation, sale, lease, or other disposition is not extended to property owned by the Issuer immediately prior thereto and is not created in contemplation of such merger, consolidation, sale, lease or other disposition;

(3) Liens on Operating Property to secure all or part of the cost of acquiring, constructing, developing, or substantially repairing, altering, or improving such property, or to secure indebtedness incurred to provide funds for any such purpose or for reimbursement of funds previously expended for any such purpose, provided such Liens are created or assumed contemporaneously with, or within eighteen (18) months after, such acquisition or completion of construction, development, or substantial repair, alteration, or improvement, provided that such Lien does not extend to any property owned by the Issuer other than the property so acquired, constructed or developed;

(4) Liens in favor of the United States of America or any State thereof, or any department, agency, or instrumentality or political subdivision of the United States of America or any State thereof, or for the benefit of holders of securities issued by any such entity, to secure any Debt incurred for the purpose of financing all or any part of the purchase price or the cost of constructing, developing, or substantially repairing, altering, or improving the property subject to such Liens;

(5) Liens on Operating Property that existed  as of the date of issuance of the Series G Notes;

(6) Liens on Operating Property to secure all or part of the costs of purchasing, transporting and handling coal for the Issuer’s electric generating stations, whether or not such purchasing, transporting and handling operations are conducted through TUCO, Inc. or a similar third party, or directly by the Issuer and its affiliates, provided that the costs

3

secured by such Liens shall not exceed $75 million in the aggregate at any time outstanding;

(7) Liens on Operating Property to secure all or part of the cost of financing of a project involving the development or expansion of property of the Issuer and  the obligee in respect of which has no recourse to the Issuer or any property of the Issuer other than the property constructed or acquired with the proceeds of such transaction or the project financed with the proceeds of such transaction (or the proceeds of such property or such project); and any refundings, refinancings and/or replacements of any such Debt by or with Debt described in clause (3) above; or

(8) any extension, renewal or replacement (or  successive  extensions, renewals, or replacements), in whole or in part, of any Lien referred to in the foregoing clauses (1) to (7), inclusive; provided, however, that the principal amount of Debt secured thereby and not otherwise authorized by said clauses (1) to (7), inclusive, shall not exceed the principal amount of Debt, plus any premium or fee payable in connection with any such extension, renewal, or replacement, so secured at the time of such extension, renewal, or replacement.

(b) Notwithstanding the provisions of Section 1.07(a), the Issuer may issue, assume, or guarantee Debt, or permit to exist Debt, secured by Liens which would otherwise be subject to the restrictions of Section 1.07(a) up to an aggregate principal amount that, together with the principal amount of all other Debt of the Issuer secured by Liens (other than Liens permitted by Section 1.07(a) that would otherwise be subject to the foregoing restrictions) and the Value of all Sale and Lease-Back Transactions in existence at such time (other than (i) any Sale and Lease-Back Transaction that, if such Sale and Lease-Back Transaction had been a Lien, would have been permitted by Section 1.07(a), (ii) Sale and Lease-Back Transactions permitted by Section 1.08 because the commitment by or on behalf of the purchaser was obtained no later than eighteen (18) months after the later of events described in (i) or (ii) of Section 1.08, and (iii) Sale and Lease-Back Transactions as to which application of amounts has been made in accordance with clause (z) of Section 1.08), does not at the time exceed the greater of fifteen percent (15%) of Net Tangible Assets or fifteen percent (15%) of Capitalization.

(c) If at any time the Issuer shall issue, assume, or guarantee any Debt secured by any Lien and if Section 1.07(a) requires that the outstanding Series G Notes be secured equally and ratably with such Debt, the Issuer will promptly execute, at its expense, any instruments necessary to so equally and ratably secure the outstanding Series G Notes and deliver the same to the Trustee along with:

(1) an Officers’ Certificate stating that the covenant of the Issuer contained in Section 1.07(a) has been complied with; and

(2) an  Opinion of Counsel to the effect that the Issuer has complied with the covenant contained in Section 1.07(a), and that any instrument executed by the Issuer in the performance of such covenant complies with the requirements of such covenant.

4

In the event that the Issuer shall hereafter secure outstanding Series G Notes equally and ratably with any other obligation or indebtedness (including other Securities) pursuant to the provisions of this Section 1.07, the Trustee is hereby authorized to enter into an indenture or agreement supplemental hereto and to take such action, if any, as it may, in its sole and absolute discretion, deem advisable to enable it to enforce effectively the rights of the Holders of outstanding Series G Notes so secured, equally and ratably with such other obligation or indebtedness.

Section 1.08.  So long as any Series G Notes are outstanding, the Issuer will not enter into or permit to exist any Sale and Lease-Back Transaction with respect to any Operating Property if, in any case, the commitment by or on behalf of the purchaser is or was obtained more than eighteen (18) months after the later of (i) the completion of the acquisition, construction, or development of such Operating Property or (ii) the placing in operation of such Operating Property or of such Operating Property as constructed, developed, or substantially repaired, altered, or improved, unless (x) the Issuer would be entitled pursuant to Section 1.07(a) to issue, assume, guarantee or permit to exist Debt secured by a Lien on such Operating Property without equally and ratably securing the Series G Notes or (y) the Issuer would be entitled pursuant to Section 1.07(b), after giving effect to such Sale and Lease-Back Transaction, to incur $1.00 of additional Debt secured by Liens (other than Liens permitted by Section 1.07(a)) or (z) the Issuer shall apply or cause to be applied, in the case of a sale or transfer for cash, an amount equal to the net proceeds thereof (but not less than the fair value (as determined by the Issuer’s Chief Financial Officer) of such Operating Property so leased) and, in the case of a sale or transfer otherwise than for cash, an amount equal to the fair value (as determined by the Board of Directors) of the Operating Property so leased, to the retirement, within one hundred eighty (180) days after the effective date of such Sale and Lease-Back Transaction, of Securities or other Debt of the Issuer ranking equally with, the Series G Notes; provided, however, that any such retirement of Securities shall be in accordance with the terms and provisions of the Indenture and the Securities; provided, further, that the amount to be applied to such retirement of Securities or other Debt shall be reduced by an amount equal to the sum of (a) an amount equal to the redemption price with respect to Securities delivered within such one hundred eighty (180)-day period to the Trustee for retirement and cancellation and (b) the principal amount, plus any premium or fee paid in connection with any redemption in accordance with the terms of other Debt voluntarily retired by the Issuer within such one hundred eighty (180)-day period, excluding in each case retirements pursuant to mandatory sinking fund or prepayment provisions and payments at maturity.

Section 1.09.      Definitions

For purposes of Section 1.07 and Section 1.08 of this Fifth Supplemental Indenture, the following terms shall have the following meanings:

“Capitalization” means the total of all the following items appearing on, or included in, the consolidated balance sheet of the Issuer: (i) liabilities for indebtedness maturing more than twelve (12) months from the date of determination; and (ii) common stock, preferred stock, premium on capital stock, capital surplus, capital in excess of par value, and retained earnings

5

(however the foregoing may be designated), less, to the extent not otherwise deducted, the cost of shares of capital stock of the Issu