AMENDMENT NO. 3 to REVOLVING CREDIT AGREEMENT

AMENDMENT NO. 3

to

REVOLVING CREDIT AGREEMENT

AMENDMENT NO. 3 (this “ Amendment ”), dated as of August 3, 2007, to the Revolving Credit Agreement, dated as of April 6, 2005, by and among SOUTHWEST GAS CORPORATION (the “ Borrower ”), the lenders listed on the signature pages thereto (the “ Lenders ”), THE BANK OF NEW YORK, as administrative agent for the Lenders (in such capacity, the “ Administrative Agent ”), BANK OF AMERICA, N.A., as Syndication Agent, and JPMORGAN CHASE BANK, N.A., UNION BANK OF CALIFORNIA, N.A. and KEYBANK NATIONAL ASSOCIATION, as Co-Documentation Agents (as amended by Amendment No. 1 to Revolving Credit Agreement, dated as of April 20, 2006, and by Amendment No. 2 to Revolving Credit Agreement, dated as of May 18, 2007, and as further amended from time to time, the “ Revolving Credit Agreement ”).

RECITALS

I.        Capitalized terms used herein that are not otherwise defined shall have the meanings assigned to such terms in the Revolving Credit Agreement.

II.              The Borrower has requested that the Administrative Agent and the Lenders agree to amend, retroactively, the Revolving Credit Agreement to change (a) the formula for calculating “Unfunded Pension Liabilities” from one based on accrued benefit obligations to one based on projected benefit obligations and (b) the threshold level on which Unfunded Pension Liabilities of a Plan would constitute an Event of Default from $50,000,000 to ten percent (10%) of the Net Worth.

III.            The Administrative Agent and the Required Lenders have advised the Borrower that they are willing to agree to the Borrower’s requests on the terms and subject to the conditions set forth in this Amendment.

NOW THEREFORE, in consideration of the covenants, conditions and agreements hereinafter set forth, and other good and valuable consideration, the receipt and adequacy of which are hereby acknowledged the parties hereto agree as follows:

(a)            Section 1.01 of the Revolving Credit Agreement is hereby amended by adding in appropriate alphabetical order the following definitions:

“ Amendment No. 3 ” means Amendment No. 3 to Revolving Credit Agreement, dated as of August 3, 2007, by and among the Borrower, the Lenders

party thereto, The Bank of New York, as Administrative Agent, Bank of America, N.A., as Syndication Agent, and JPMorgan Chase Bank, N.A., Union Bank of California, N.A. and KeyBank National Association, as Co-Documentation Agents.

“ Projected Benefit Obligations ” means, as of any date, the actuarial present value of Pension Plan benefits attributed to employee service to such date measured using assumptions as to future compensation levels.

“ Regulatory Assets ” means certain assets of the Borrower or an ERISA Affiliate which represent future probable increases in revenues to be recorded by the Borrower or such ERISA Affiliate associated with Pension Plan liabilities incurred by the Borrower or such ERISA Affiliate, to the extent permitted to be recorded as such under Statement of Financial Accounting Standards No. 71.

(b)            Section 1.01 of the Revolving Credit Agreement is hereby amended by deleting the definition of “ Unfunded Pension Liabilities ” in its entirety and substituting the following therefor:

“ Unfunded Pension Liabilities ” means, as of the end of any fiscal year of the Borrower (or more frequently, if such calculation is required to be made more frequently by law or by GAAP), (a) a Plan’s Projected Benefit Obligations minus (b) the current value of that Plan’s assets, as defined in Section 3(26) of ERISA, plus Regulatory Assets.

(c)            Section 5.01(g)(iv) of the Revolving Credit Agreement is hereby amended by deleting the text thereof and substituting the following therefor:

“None of the Qualified Plans subject to Title IV of ERISA has any Unfunded Pension Liability in excess of ten percent (10%) of the Net Worth as to which the Borrower is or may be liable.”

(d)            Section 8.01(j) of the Revolving Credit Agreement is hereby amended by deleting the text thereof and sub