Exhibit 4(x)

[EXECUTION COPY]

AMENDMENT NO. 1
TO
AMENDED AND RESTATED CREDIT AGREEMENT

This AMENDMENT NO. 1, dated as of April 30, 2007 (this “Amendment”), is made by and among UNS ELECTRIC, INC., an Arizona corporation (“UNS Electric”), UNS GAS, INC., an Arizona corporation (“UNS Gas”, and together with UNS Electric being referred to herein, individually, as a “Borrower” and, collectively, as the “Borrowers”), UNISOURCE ENERGY SERVICES, INC., an Arizona corporation (the “Guarantor”), the lenders listed on the signature pages of this Amendment as “Lenders” (such lenders, together with their respective permitted assignees from time to time, being referred to herein, collectively, as the “Lenders”), and UNION BANK OF CALIFORNIA, N.A., as administrative agent for the Lenders (in such capacity, the “Administrative Agent”).

PRELIMINARY STATEMENT:

The Borrowers, the Guarantor, the Lenders and the Administrative Agent previously entered into that certain Amended and Restated Credit Agreement, dated as of August 11, 2006 (the “Existing Agreement”, as amended by this Amendment, the “Amended Agreement”, and as the Amended Agreement may hereafter be amended, supplemented or otherwise modified from time to time, the “Credit Agreement”). The Borrowers and the Lenders desire to amend the Existing Agreement in certain particulars in connection with the Order (Decision No. 69395) issued by the ACC on March 22, 2007. Each of the Borrowers, the Guarantor and the Required Lenders has agreed to such amendment, on the terms and conditions set forth herein. The parties therefore agree as follows (capitalized terms used but not defined herein having the meanings assigned such terms in the Existing Agreement):

SECTION 1.  Amendments to Existing Agreement. The Existing Agreement is, effective as of the date hereof and subject to the satisfaction of the conditions precedent set forth in Section 2 hereof, hereby amended as follows:

(a) Definitions. The following new definition is hereby added to Section 1.01 of the Existing Agreement in the appropriate alphabetical order:

“2007 ACC Order” means the Order (Decision No. 69395) issued by the ACC on March 22, 2007.

(b) Governmental Authorizations. Section 7.01(g) of the Existing Agreement is hereby amended and restated in its entirety to read as follows:

“(g) Governmental Authorizations, etc. No consent, approval or authorization of, or registration, filing or declaration with, any Governmental Authority is required in connection with the execution, delivery or performance by such Obligor of any Loan Document to which it is a party, except for (i) the ACC Order, which ACC Order has been obtained and is in full force and effect, and (ii) the 2007 ACC Order, which 2007 ACC Order has been obtained and is in full force and effect. After giving effect to each Extension of Credit to or for the account of any Borrower and the application of the proceeds thereof, such Borrower is in compliance with all applicable requirements contained in the 2007 ACC Order (including, without limitation, the requirement that such Borrower’s equity shall not be less than 30% of its total capital after giving effect to such Extension of Credit, if such Extension of Credit is made on or after the date of issuance by UNS Electric of long term debt pursuant to the authority granted in the 2007 ACC Order).”

SECTION 2.  Conditions of Effectiveness of Amendments. The amendments to the Existing Agreement set forth in Section 1 hereof shall become effective as of the date hereof when, and only when, the Administrative Agent shall have received counterparts of this Amendment executed by the Borrowers, the Guarantor and the Required Lenders (in sufficient quantity for each party to have a fully executed original).

SECTION 3.  Representations and Warranties of the Borrowers. Each Borrower represents and warrants as follows:

(a) The execution and delivery by such Borrower of this Amendment, and the performance by such Borrower of this Amendment and the Amended Agreement, are within such Borrower’s organizational powers and have been duly authorized by all necessary corporate and, if required, stockholder action, and do not and will not (i) violate any Requirement of Law, (ii) violate or result in a default under any indenture, agreement or other instrument binding upon such Borrower or any of its Subsidiaries or its assets, or give rise to a right thereunder to require any payment to be made by such Borrower or any of its Subsidiaries, or (iii) result in the creation or imposition of any Lien on any asset of such Borrower or any of its Subsidiaries. This Amendment has been duly executed and delivered by such Borrower.

(b) The execution and delivery by such Borrower of this Amendment, and the performance by such Borrower of this Amendment and the Amended Agreement, do not require any consent or approval of, registration or filing with, or any other action by, any Governmental Authority, except as set forth in Section 7.01(g) of the Amended Agreement.

(c) Each of this Amendment and the Amended Agreement constitutes a legal, valid and binding obligation of such Borrower, enforceable in accordance with its terms, subject to applicable bankruptcy, insolvency, reorganization, moratorium or other laws affecting the enforcement of creditors’ rights generally and subject to general principles of equity, regardless of whether considered in a proceeding in equity or at law.

(d) No Default or Event of Default with respect to such Borrower or the Guarantor has occurred and is continuing.

SECTION 4.  Reference to and Effect on the Existing Agreement. (a) Upon the effectiveness of this Amendment: (i) each reference in the Existing Agreement to “this Agreement”, “hereunder”, “hereof” or words of like import referring to the Existing Agreement shall mean and be a reference to the Credit Agreement; and (ii) each reference in any other Loan Document to “the Credit Agreement”, “thereunder”, “thereof” or words of like import referring to the Existing Agreement shall mean and be a reference to the Credit Agreement.

(b) Except as specifically amended above, the Existing Agreement shall continue to be in full force and effect and is hereby in all respects ratified and confirmed.

(c) The execution, delivery and effectiveness of this Amendment shall not, except as expressly provided herein, operate as a waiver of any right, power or remedy of the Lenders, the Issuing Banks or the Administrative Agent under the Existing Agreement or any other Loan Document, nor constitute a waiver of any provision of the Existing Agreement or any other Loan Document.

SECTION 5.  Costs and Expenses. The Borrowers agree to pay on demand all reasonable out-of-pocket expenses of the Administrative Agent in connection with the preparation, negotiation, syndication, execution and delivery of this Amendment and the other instruments and documents to be delivered hereunder, including, without limitation, the reasonable fees, charges and disbursements of counsel to the Administrative Agent with respect thereto and with respect to advising the Administrative Agent as to its rights and responsibilities hereunder and thereunder, and all out-of-pocket expenses incurred by the Administrative Agent, any Issuing Bank or any Lender (including, without limitation, the fees, charges and disbursements of any counsel for the Administrative Agent, any Issuing Bank or any Lender) in connection with the enforcement (whether through negotiations, legal proceedings or otherwise) of this Amendment.

SECTION 6.  Execution in Counterparts. This Amendment may be executed in any number of counterparts and by different parties hereto in separate counterparts, each of which when so executed and delivered shall be deemed to be an original and all of which taken together shall constitute but one and the same instrument. In furtherance of the foregoing, it is understood and agreed that signatures hereto submitted by facsimile transmission shall be deemed to be, and shall constitute, original signatures.

SECTION 7.  Governing Law. This Amendment shall be governed by, and construed in accordance with, the laws of the State of the New York.

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IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed by their respective officers thereunto duly authorized, as of the date first above written.