For the fiscal year ended December 31, 2015

Commission file number 1-7850

Full title of the plan and the address of the plan, if different from that of the issuer named below:


Name of issuer of the securities held pursuant to the plan and the address of its principle executive office:


5241 Spring Mountain Road, Post Office Box 98510
Las Vegas, Nevada 89193-8510
(702) 876-7237




Listed below are all financial statements and exhibits filed as part of this annual report:

Financial statements, including statements of net assets available for benefits as of December 31, 2015 and 2014, and the related statement of changes in net assets available for benefits for the year ended December 31, 2015 and notes to financial statements, together with the report thereon of PricewaterhouseCoopers LLP, independent registered public accounting firm.

Supplemental Schedule: Schedule H, Line 4i - Schedule of Assets (Held at End of Year).  All other schedules required by Section 2520.103-10 of the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974 and not included herein have been omitted because they are not applicable.
Consent of PricewaterhouseCoopers LLP, independent registered public accounting firm.

Pursuant to the requirements of the Securities Exchange Act of 1934, the members of the Southwest Gas Corporation Benefits Committee have duly caused this annual report to be signed by the undersigned hereunto duly authorized.


/s/ Roy R. Centrella
Roy R. Centrella
Senior Vice President/
Chief Financial Officer
Southwest Gas Corporation

Dated:  June 21, 2016






AS OF DECEMBER 31, 2015 AND 2014 AND



Report of Independent Registered Public Accounting Firm

To the Administrator of Southwest Gas Corporation Employees’ Investment Plan

In our opinion, the accompanying statements of net assets available for benefits and the related statement of changes in net assets available for benefits present fairly, in all material respects, the net assets available for benefits of Southwest Gas Corporation Employees’ Investment Plan (the “Plan”) at December 31, 2015 and 2014, and the changes in net assets available for benefits for the year ended December 31, 2015 in conformity with accounting principles generally accepted in the United States of America.  These financial statements are the responsibility of the Plan’s management.  Our responsibility is to express an opinion on these financial statements based on our audits.  We conducted our audits of these statements in accordance with the standards of the Public Company Accounting Oversight Board (United States).  Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement.  An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation.  We believe that our audits provide a reasonable basis for our opinion.

The supplemental Schedule of Assets (Held at End of Year) at December 31, 2015 has been subjected to audit procedures performed in conjunction with the audit of the Plan’s financial statements.  The supplemental schedule is the responsibility of the Plan’s management.  Our audit procedures included determining whether the supplemental schedule reconciles to the financial statements or the underlying accounting and other records, as applicable, and performing procedures to test the completeness and accuracy of the information presented in the supplemental schedule. In forming our opinion on the supplemental schedule, we evaluated whether the supplemental schedule, including its form and content, is presented in conformity with the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974.  In our opinion, the Schedule of Assets (Held at End of Year) at December 31, 2015 is fairly stated, in all material respects, in relation to the financial statements as a whole.

/s/ PricewaterhouseCoopers LLP
Las Vegas, Nevada
June 21, 2016



Statements of Net Assets Available for Benefits
December 31,
   Investments at fair value (see Notes 2 and 6)
  $ 371,760,413     $ 399,532,894  
   Notes receivable from participants (see Note 2)
    7,635,141       7,690,818  
   Other receivables (see Note 2)
    -       934,539  
   Contribution receivable from employer
    68,577       51,021  
      Total assets
    379,464,131       408,209,272  
Net assets available for benefits
  $ 379,464,131     $ 408,209,272  
The accompanying notes are an integral part of these statements.



Statement of Changes in Net Assets Available for Benefits
Year Ended
December 31,
   Additions to net assets attributed to:
      Investment income:
         Net depreciation in fair value of investments
  $ (18,355,085 )
         Interest and dividends
      Net investment income (loss)
    (3,454,369 )
      Interest on participant loans
   Other income
   Total additions
   Deductions from net assets attributed to:
      Benefits paid to participants
      Other expenses
   Total deductions
   Net increase (decrease) in net assets available for benefits
    (28,745,141 )
Net assets available for benefits:
   Beginning of year
   End of year
  $ 379,464,131  
The accompanying notes are an integral part of this statement.



(1) Description of Plan

The following description of the Southwest Gas Corporation Employees’ Investment Plan (the “Plan”), as amended, provides general information.  Participants should refer to the Plan document for a more complete description of the Plan’s provisions.


The Plan is a voluntary defined contribution plan covering all employees of Southwest Gas Corporation (the “Company”).  It is subject to the provisions of the Employee Retirement Income Security Act of 1974 (“ERISA”).  The Plan’s assets invested in Company stock (consisting of (i) Company matching contributions and (ii) participant deferrals) are designated as an Employee Stock Ownership Plan (“ESOP”).  New employees are automatically enrolled in the Plan after 30 days unless they elect not to participate.

The ESOP invests primarily in qualifying employer securities.  The non-ESOP portion of the Plan is a profit-sharing plan that is qualified under Code Sections 401(a) and 401(k).  The ESOP portion of the Plan is a stock bonus plan and an employee stock ownership plan that is qualified under Code Sections 401(a) and 4975(e)(7) and described in ERISA Section 407(d)(6).  The profit-sharing plan and the ESOP together are a single plan under Treasury Regulation Section 1.414(1)-1(b)(1).  The Plan satisfies the requirements of ERISA and the trust fund maintained under the Plan is tax-exempt under Code Section 501(a).


Participants may contribute from 2% to 60% of their annual base wages.  However, contributions may not exceed amounts promulgated by the Internal Revenue Code.  The Company contributes to the Plan an amount equal to 50% of a participant’s contribution.  The Company’s maximum contribution is 3.5% of a participant’s annual base compensation.  Deferral percentages elected by participants are also applied to overtime earnings, however they are not matched by the Company.

Participants’ Accounts

Each participant account is credited with the participant’s contribution and the portion contributed by the Company.  The portion contributed by the participant is invested in the various funds according to the direction of the participant.  Beginning in January 2015, all employees, regardless of age, are also able to choose investment options for the Company matching contributions.


Participants are immediately vested in their voluntary contributions plus actual earnings thereon.  Vesting in the contributions made by the Company and in the earnings thereon is based on years of continuous service.  Participants are fully vested in dividends paid in the Southwest Gas Stock Fund without regard to whether the participant is vested in the Southwest Gas stock with respect to which the dividend is paid.  The following table shows the vesting schedule of Company contributions and the earnings thereon (other than dividends on the Southwest Gas Stock Fund).

Years of Service
One but less than two 
Two but less than three
Three but less than four
Four but less than five
Five and over



In the event of death, attainment of age 65, or total disability of a participant, or Plan termination, Company contributions become fully vested irrespective of the years of service.Forfeitures as a result of a participant’s termination prior to vesting, that are not utilized to restore prior benefits or to pay benefits to previously unlocated participants and beneficiaries, are reallocated to the remaining participants on a quarterly basis based on the employer contribution ratio.  For the years ended December 31, 2015 and 2014, forfeitures of non-vested accounts reallocated to participants were approximately $55,000 and $44,000, respectively.

Notes Receivable from Participants (Participant Loans)

The Plan provides that participants may borrow against the contribution and rollover balances in their accounts, subject to certain limitations specified in the Plan.  Funds for loans are obtained through the liquidation of participants’ investment accounts. Payments on the loans include interest at a rate that approximates the prime rate, plus 2%.  At December 31, 2015, all outstanding loans had an annual interest rate of 5.25% maturing through 2020.  Principal and interest payments on a participant’s loan will be credited to the participant’s contribution and rollover accounts in the same ratio as ongoing investment elections. The maximum repayment period for participant loans is five years.

Payment of Benefits

If a participant terminates employment with the Company as a result of retirement, death, or permanent and total disability, such participant, or designated beneficiary in the case of death, will be entitled to receive an amount equal to the value of his account as soon as practicable following termination of employment.  Distributions from the Southwest Gas Stock Fund will be made in the Company’s common stock plus cash in lieu of fractional shares.  A participant may apply to the Plan Committee to request a single lump sum payment in cash for the value of the Company’s common stock otherwise distributable to the participant.  Lump sum distributions from other funds will be paid in cash.

Distributions under the Plan will begin as soon as practicable, but not later than April 1 following the end of the Plan year in which the participant attains age 70-1/2 or terminates employment, if later.  If the participant’s vested account balance is less than $5,000, the participant may request a lump-sum distribution or direct that the amount be rolled-over into an Individual Retirement Account (“IRA”).  If no election is made and the balance does not exceed $1,000, it will be distributed to the participant.  If no election is made and the balance is greater than $1,000 but does not exceed $5,000, it will be rolled over to an individual retirement account, designated by the committee which administers the Plan, for the benefit of the participant.  If the participant’s vested account balance is greater than $5,000, the participant may remain in the Plan, receive a lump-sum distribution, or roll-over the account into an IRA.  In this case, a participant who is terminated and does not elect to take a distribution will continue to receive his share of investment income on all vested portions of his accounts until electing to receive distributions from the Plan.  Beneficiaries of a participant have no more than five years after the participant’s death to request payment.
A participant or surviving spouse, if the designated beneficiary, is permitted to make partial withdrawals as long as minimum distribution requirements are met.

Plan Expenses

Plan-related expenses and any other costs of administering the Plan will be paid with funds from the Plan unless paid by the Company at its discretion.  The Company paid all administrative Plan expenses, except loan origination and maintenance fees, during 2015.  Loan origination and maintenance fees paid by Plan participants for the year ended December 31, 2015 were $42,176.



Other Income

The Plan participates in Fidelity’s revenue credit program which allows the Plan sponsor to apply credits received to pay for ERISA qualified expenses and/or allocate credits to participants via the Plan-level pro-rata method. These revenue credits qualify as party-in-interest transactions for which a statutory exemption exists.

Plan Administration

Fidelity Management Trust Company acts as the trustee and Fidelity Investments Institutional Operations Company performs all recordkeeping of the Plan.

(2) Summary of Accounting Policies

The following information describes the Plan’s accounting policies:

Basis of Accounting

The financial statements of the Plan are prepared under the accrual method of accounting.

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles (“GAAP”) in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of changes in net assets during the reporting period.  Actual results could differ from those estimates.

Investment Valuation and Income Recognition

Investments are reported at fair value.  Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.  See Note 6 for a discussion of fair value measurements.

Purchases and sales of securities are generally valued on an end-of-trade-date pricing basis with the exception of exchanges in and out of the Southwest Gas stock fund.  When buying Company stock, the stock purchase will be processed on the trade date in real-time pricing.  When selling Company stock, the stock sale will be processed on the trade date in real-time pricing, and the exchange into another investment option will be processed three business days after the trade date (in accordance with normal securities settlement practice).  Exchanges in and out of Company stock are generally reflected in participant accounts the day following the trade date.  Contributions, loans, and withdrawals involving Company stock are not subject to real-time trading.  Dividends are recorded on the ex-dividend date.

Notes Receivable from Participants

Notes receivable from participants (participant loans) are measured at their unpaid principal balance plus any accrued but unpaid interest.  No allowance for credit losses has been recorded at December 31, 2015 or 2014.

Other Receivables

Other receivables consist primarily of unsettled trades.



Risks and Uncertainties

Investment securities, in general, are exposed to various risks, such as interest rate, credit, and overall market volatility risks as well as changes in prevailing market and interest rates, increases in defaults and credit rating downgrades.  Due to the level of risk associated with certain investment securities and the amount invested in the Company’s common stock, it is reasonably possible that changes in the values of investment securities will occur in the near term and such changes could materially affect the amounts reported in the statements of net assets available for benefits.

Payment of Benefits

Benefits are recorded when paid.

Early adoption of Recently Issued Accounting Standard Updates (“ASU”) No. 2015-12

In July 2015, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2015-12 “Plan Accounting: Defined Benefit Pension Plans, Defined Contribution Pension Plans and Health and Welfare Benefit Plans.”  This update is comprised of three parts.  Part I of the update reduces the cost and complexity of reporting for fully benefit-responsive investment contracts (“FBRIC”) by requiring FBRICs to be measured, presented and disclosed at contract value.  Part II of the update eliminates the requirement for disclosure of: i) individual investments that represent 5% or more of net assets available for benefits; and ii) Net appreciation or depreciation for investments disaggregated by general type – net appreciation or depreciation will only be required to be presented in the aggregate.  Investments will only be grouped by general type (e.g., equity, bonds, mutual funds, etc.), eliminating the need to disaggregate investments on the basis of nature, characteristics, and risks.  These changes impact presentation and disclosures only and have no impact on net assets available for benefits.  Part III of the update reduces the complexity in employee benefit plan accounting by providing a practical expedient that permits plans to measure investments and investment-related accounts as of a month-end date that is closest to the plan’s fiscal year-end, when the fiscal period does not coincide with month-end.  Parts I and III are not applicable to the Plan.  Early application is permitted.  The Plan adopted this update as of December 31, 2015 and has applied the guidance retrospectively as noted below in (6) Fair Value Measurements.

(3) Related-Party and Party-In-Interest Transactions

Since the Company’s common stock is an investment held by the Plan, investments in this common stock represent transactions with parties-in-interest.  Certain other plan investments are short-term deposits and investments, and shares of mutual funds managed by Fidelity Management Trust Company, the Trustee as defined by the Plan.  These certain plan investments qualify as party-in-interest transactions for which a statutory exemption exists.  During the year ended December 31, 2015, the Plan made purchases (and share dividend accumulations) totaling approximately $11.8 million and sales (including distributions) of approximately $18.5 million of Company common stock.  Participant loans qualify as party-in-interest transactions.  At December 31, 2015 and 2014, participant loans were $7,635,141 and $7,690,818, respectively.  Fees paid by participants to the Trustee for administrative services were $42,176 for the year ended December 31, 2015.  The following table represents investments held by related parties:

December 31,
Southwest Gas Corporation
  $ 83,847,951     $ 100,985,127  
Fidelity Management Trust Company
    204,409,909       210,972,680  
    $ 288,257,860     $ 311,957,807  



(4) Plan Termination

Although the Company expects to continue the Plan indefinitely, it reserves the right to amend or terminate the Plan at any time.  Upon termination, partial termination, or complete discontinuance of contributions to the Plan, Company contributions will become fully vested.

(5) Federal Income Taxes

In September 2013, the Company received a favorable determination letter from the Internal Revenue Service (“IRS”) stating that the Plan, amended and restated effective January 1, 2010, qualifies for deferred tax treatment of contributions under Section 401(k) of the Internal Revenue Code (“IRC”).  Although the Plan has been amended since January 1, 2010, the Plan administrator and the Plan’s tax counsel believe that the Plan is designed and is currently being operated in compliance with the applicable requirements of the IRC.

Accounting principles generally accepted in the United States of America require Plan management to evaluate tax positions taken by the Plan.  Management evaluated the Plan's tax positions and concluded that the Plan has maintained its tax exempt status and has taken no uncertain tax positions that require recognition or disclosure in the financial statements.  The Plan is subject to routine audits by taxing jurisdictions and in May 2015, the Plan was notified by the IRS that an examination would be conducted.  The examination for Plan years 2013 and 2014 was completed on January 28, 2016 and no changes to reported amounts were made.  The Plan administrator believes it is no longer subject to income tax examinations for years prior to 2015.

(6) Fair Value Measurements

U.S. GAAP states that a fair value measurement should be based on the assumptions that market participants would use in pricing the asset or liability, and establishes a fair value hierarchy that ranks the inputs used to measure fair value by their reliability.  The three levels of the fair value hierarchy are as follows:

Level 1 - quoted prices (unadjusted) in active markets for identical assets or liabilities that a company has the ability to access at the measurement date.

Level 2 - inputs other than quoted prices included within Level 1 that are observable for similar assets or liabilities, either directly or indirectly.

Level 3 - unobservable inputs for the asset or liability. Unobservable inputs are used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date.

The Plan provides for investments in various investment securities including common stock of the Company. The assets held by the Plan, excluding temporary cash investments, are traded in active exchange markets; their estimated fair values were determined at December 31, 2015 using published market closing prices.  Shares of mutual funds are valued at the net asset value (“NAV”) of shares held by the Plan at year-end.  However, as these funds are actively traded, the NAV in these cases is the fair value, and not a practical expedient utilized in lieu of an available fair value.  There have been no changes in fair value methodologies used at December 31, 2015.

The following table sets forth, by level within the three-level fair value hierarchy, the Plan’s assets that were accounted for at fair value.  The FASB issued guidance in 2015, which the Plan has adopted early as permitted, eliminating the need to disaggregate investments on the basis of nature, characteristics, and risks.  The 2014 table has been conformed to follow this guidance.  See Note 2 regarding the early adoption.  The following table sets forth, by level within the fair value hierarchy, the Plan’s assets that were accounted for at fair value.



Level 1 - Quoted Prices in Active Markets for Identical Financial Assets
December 31, 2015
December 31, 2014
Assets at fair value:
  Mutual funds:
  $ 156,567,958     $ 162,876,000  
    Equity and bond/life cycle
    83,811,443       85,063,938  
    18,594,689       20,224,556  
    Money market mutual fund
    28,936,782       30,381,676  
      287,910,872       298,546,170  
  Southwest Gas Corporation common stock
    83,847,951       100,985,127  
  Temporary cash investments
    1,590       1,597  
Total level 1 assets
  $ 371,760,413     $ 399,532,894  

No assets fell within Level 2 or 3 of the fair value hierarchy.

As noted above, the mutual funds and Southwest Gas Corporation common stock held by the Plan are listed and regularly traded on a national securities exchange.  The values of mutual funds are generally determined based on the NAV of the funds, that is, the total value of the securities in the funds less the amount of any liabilities outstanding, the result of which is divided by the fund shares outstanding.  The funds are traded at the NAV, which is determined once each day.  Southwest Gas Stock is traded in real time. The values in the above table were based on pricing as of the last business day of the calendar year.

Equity – The equity funds consist of small, medium, and large capitalization funds, as well as an international fund.  They invest primarily in common stocks of various-sized U.S. and foreign issuers.  Most of the funds select investments by analyzing each issuer’s financial condition and industry position, as well as market and economic conditions, but the large capitalization fund uses a “passive management” approach to replicate the Standard & Poor’s 500 Index.

Equity and Bond/Life Cycle Funds - The equity and bond/life cycle funds include a combination of underlying equity, fixed-income, and short-term funds using an asset allocation strategy appropriate for specific retirement dates.  As the retirement date approaches, the asset allocation strategy becomes increasingly conservative. Ultimately, each life cycle fund will merge with the Freedom K Income Fund, which is designed for people already retired.

Bond - The bond fund employs a “passive management” or indexing investment approach designed to track the performance of the Barclays U.S. Aggregate Bond Index.  This index represents a wide spectrum of public, investment-grade, taxable, and fixed income securities in the United States, including government, corporate, and international dollar-denominated bonds, as well as mortgage-backed and asset-backed securities, all with maturities of more than one year.

Money Market - The money market mutual fund invests in United States dollar-denominated money market securities of domestic and foreign issuers and repurchase agreements and potentially enters into reverse purchase agreements, with more than 25% of total assets in the financial services industry.  The investing is in compliance with industry-standard requirements for money market funds for the quality, maturity, and diversification of investments.

The investment objectives and strategies for the Plan are designed to provide a diversified group of investments offering competitive levels of yield and prudent assumptions of investment risk, to enhance capital and maintain liquidity.

(7) Subsequent Events

Management of the Plan monitors events occurring after the Statement of Net Assets Available for Benefits date and through the issuance of the financial statements to determine the impacts, if any, of events on the financial statements to be issued or disclosures to be made, and has reflected them where appropriate.



            SCHEDULE I  
E.I.N. 88-0085720
AT DECEMBER 31, 2015
Identity and Description of
Number of
Southwest Gas Corporation Common Stock
    1,520,086     $ 83,847,951  
Brown Capital Management, Inc. Small Company Institutional Fund
    211,803       15,264,646  
Vanguard Institutional Index Fund
    84,081       15,691,143  
T. Rowe Price Institutional Large Cap Value Fund
    600,411       11,275,723  
Fidelity Contrafund Class K
    671,789       66,426,525  
Fidelity Freedom 2005 Fund Class K
    25,029       309,858  
Fidelity Freedom 2010 Fund Class K
    236,348       2,916,532  
Fidelity Freedom 2015 Fund Class K
    902,308       11,549,537  
Fidelity Freedom 2020 Fund Class K
    1,914,657       25,886,156  
Fidelity Freedom 2025 Fund Class K
    780,716       11,008,101  
Fidelity Freedom 2030 Fund Class K
    777,075       11,135,488  
Fidelity Freedom 2035 Fund Class K
    302,369       4,462,964  
Fidelity Freedom 2040 Fund Class K
    431,673       6,384,445  
Fidelity Freedom 2045 Fund Class K
    239,445       3,641,951  
Fidelity Freedom 2050 Fund Class K
    184,792       2,832,856  
Fidelity Freedom 2055 Fund Class K
    83,472       947,412  
Fidelity Freedom 2060 Fund Class K
    3,985       39,328  
Fidelity Freedom Income Fund Class K
    237,396       2,696,815  
Fidelity Low-Priced Stock Fund Class K
    528,895       25,233,569  
Fidelity Institutional Money Market Fund
    28,935,159       28,935,159  
Metwest Total Return Bond I Fund
    1,750,912       18,594,689  
Fidelity Government Money Market Fund - Premium Class
    1,623       1,623  
Vanguard International Growth Fund Admiral Shares
    151,514       10,160,538  
Victory Integrity Small Cap Value Class R6 Fund
    402,050       12,515,814  
Temporary Cash Investments
Participant Loans (with interest at a rate of 5.25%)
                  $ 379,395,554  
*  A party-in-interest for which a statutory exemption exists.




Consent of Independent Registered Public Accounting Firm
We hereby consent to the incorporation by reference in the Registration Statement on Form S-8 (No. 333-155581) of Southwest Gas Corporation of our report dated June 21, 2016 relating to the financial statements and supplemental schedule of Southwest Gas Corporation Employees' Investment Plan, which appears in this Form 11-K.

/s/ PricewaterhouseCoopers LLP
Las Vegas, Nevada
June 21, 2016