SWX Southwest Gas Holdings Inc

THE SPECIAL MEETING PROPOSAL

Proposal 5: Resolution To Call a Special Meeting to Permit the Nomination of the Icahn Nominees

(Proposal 5 on the GOLD proxy card)

At the Annual Meeting, Icahn Partners and the other Participants will propose that the Company’s stockholders adopt the Special Meeting Proposal, the purpose of which is to approve the calling of a special meeting of the Company’s stockholders and otherwise permit the actions necessary to cause the Board to undertake the actions necessary to permit the nomination of the Icahn Nominees. The following is the text of the Special Meeting Proposal:

“RESOLVED, that the stockholders of Southwest Gas Holdings, Inc. (the “Company”) hereby approve a proposal by Icahn Partners LP to call a special meeting of stockholders of the Company. At that special meeting the Board of Directors of the Company shall undertake such actions so as to permit the nomination of the slate of ten (10) directors (or such greater number of directors as may be nominated by Icahn Partners LP in the event the Company increases the number of directors up for election at the Annual Meeting) as originally proposed by Icahn Partners and its affiliates for election at the Annual Meeting. Such special meeting shall be held at the principal executive offices of the Company no later than 45 days following the date of receipt of all required governmental or regulatory approvals, consents, clearances or waivers which, in each case, have not been appealed and are no longer appealable, only if it is determined that such regulatory approvals are required to be obtained despite structuring the closing of the Icahn tender offer to avoid the need for any such approvals, in order for the nominees of Icahn Partners LP to serve on the Board of Directors of the Company.”

If it is determined, despite structuring the closing of the Icahn tender offer to avoid such requirements, that governmental or regulatory approvals, consents, clearances or waivers are required, then it may be necessary for the Icahn Nominees not to be seated on the Board until such time as the applicable approvals, consents, clearances or waivers have been obtained. In order to address a situation where the Icahn Nominees were unable to be elected and/or seated at the Annual Meeting, or were elected and unable to be seated, in accordance with applicable regulatory requirements, we have included the Special Meeting Proposal to allow the Company’s stockholders to vote on a proposal at the Annual Meeting that approves and requires the calling of a special meeting of the Company’s stockholders requiring the Board put forth at such special meeting any matters that may be required to provide for the election and/or seating of the Icahn Nominees following the satisfaction of the requisite regulatory approvals. The purpose of the calling of the Special Meeting would be to allow the Company’s stockholders to vote for the election and/or seating the Icahn Slate once the requisite regulatory approvals have been satisfied (rather than requiring the stockholders to wait until the Company’s 2023 Annual Meeting to consider the Icahn Slate).

The Special Meeting Proposal will be approved if it receives the affirmative vote of the holders of not less than one-third (1/3) of the Company’s issued and outstanding shares, as this is the threshold share amount that is needed for shareholders to approve the calling of a Special Meeting. Abstentions and broker non-votes with respect to the Special Meeting Proposal will have the effect of a vote “against” the Special Meeting Proposal.

WE STRONGLY URGE YOU TO VOTE “FOR” THE SPECIAL MEETING PROPOSAL BY MARKING, SIGNING, DATING AND RETURNING THE ENCLOSED GOLD PROXY CARD OR, IF APPLICABLE, THE ENCLOSED GOLD VOTING INSTRUCTION FORM USING THE POSTAGE-PAID ENVELOPE PROVIDED TO YOU WITH THIS PROXY STATEMENT. IF YOUR SHARES ARE HELD FOR YOU BY A CUSTODIAN BROKER OR BANK, YOU ALSO MAY BE ABLE TO VOTE YOUR SHARES BY TELEPHONE OR INTERNET BY FOLLOWING THE INSTRUCTIONS PROVIDED BY YOUR CUSTODIAN BROKER OR BANK. IF YOU HAVE SIGNED THE GOLD PROXY CARD OR, IF APPLICABLE, THE GOLD VOTING INSTRUCTION FORM AND NO MARKING IS MADE, YOU WILL BE DEEMED TO HAVE GIVEN A DIRECTION TO VOTE ALL THE SHARES OF COMMON STOCK REPRESENTED BY THE GOLD PROXY CARD OR, IF APPLICABLE, THE GOLD VOTING INSTRUCTION FORM “FOR” THE SPECIAL MEETING PROPOSAL.

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Other Proposals

Except as set forth in this Proxy Statement, the Icahn Participants are not aware of any other matter to be considered at the Annual Meeting. However, if the Icahn Participants learn of any other proposals made at a reasonable time before the Annual Meeting, the Icahn Participants will either supplement this Proxy Statement and provide stockholders with an opportunity to vote by proxy directly on such matters or will not exercise discretionary authority with respect thereto. If other proposals are made thereafter, the persons named as proxies on the GOLD proxy card solicited by the Icahn Participants will vote such proxies in their discretion.

If you sign and return the GOLD proxy card or, if applicable, the GOLD voting instruction form, your Shares will be voted in accordance with your specifications. If no direction is indicated with respect to the foregoing proposals, you will be deemed to have given a direction to vote the Shares represented by the GOLD proxy card or, if applicable, the GOLD voting instruction form (1) “FOR” all nominees set forth in Proposal 1, (2) “AGAINST” the approval, on an advisory basis, of the compensation of the Company’s named executive officers, (3) “FOR” the ratification of the selection of PricewaterhouseCoopers LLP as the independent registered public accounting firm for the Company for fiscal year 2022, (4) “FOR” the Bylaw Restoration Proposal, (5) “FOR” the Special Meeting Proposal, and (6) in the proxy holders’ discretion as to other matters that may come before the Annual Meeting.

The Company has set the close of business on March 21, 2022 as the Record Date for determining stockholders entitled to notice of and to vote at the Annual Meeting. The mailing address of the principal executive offices of the Company is 8360 S. Durango Drive, Post Office Box 98510, Las Vegas, Nevada 89193-8510. Stockholders of record at the close of business on the Record Date will be entitled to vote at the Annual Meeting. According to the Company, as of the Record Date, there were 60,523,873 Shares outstanding.

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VOTING AND PROXY PROCEDURES

Voting and Proxy Procedures

Only stockholders of record on the Record Date will be entitled to notice of and to vote at the Annual Meeting. Stockholders who sell their Shares before the Record Date (or acquire them without voting rights after the Record Date) may not vote such Shares. Stockholders of record on the Record Date will retain their voting rights in connection with the Annual Meeting even if they sell their Shares after the Record Date.

Stockholders of Record: If your Shares are held in your own name, please authorize a proxy to vote by signing and returning the enclosed GOLD proxy card using the postage-paid envelope provided.

Street Name Holders: If you hold your Shares in the name of one or more banks, brokerage firms, dealers, trust companies or other custodians, only they can vote your Shares and only upon receipt of your specific instructions. Accordingly, you should complete, sign, date and return the enclosed GOLD voting instruction form or vote by telephone or Internet by following the directions provided to you by your broker or bank custodian or contact the person responsible for your account and give instructions to them to sign and return a GOLD proxy card representing your Shares to elect the Icahn Nominees to the Board, to approve the Bylaw Restoration Proposal and to approve the Special Meeting Proposal.

Shares represented by properly executed GOLD proxy cards will be voted at the Annual Meeting as marked.

If a stockholder returns a GOLD proxy card or, if applicable, a GOLD voting instruction form that is signed, dated and not marked with respect to the proposals, that stockholder will be deemed to have given direction to vote (1) “FOR” all nominees set forth in Proposal 1, (2) “AGAINST” the approval, on an advisory basis, of the compensation of the Company’s named executive officers, (3) “FOR” the ratification of the selection of

PricewaterhouseCoopers LLP as the independent registered public accounting firm for the Company for fiscal year 2022, (4) “FOR” the Bylaw Restoration Proposal, (5) “FOR” the Special Meeting Proposal, and (6) in the proxy holders’ discretion as to other matters that may come before the Annual Meeting.

Quorum; Broker Non-Votes; Discretionary Voting

A quorum is the minimum number of Shares that must be represented at a duly called meeting of stockholders virtually or represented by proxy, in order to legally conduct business at the meeting. According to Southwest Gas’ proxy statement, a quorum requires the presence of the holders of a majority of the Shares entitled to vote represented in person or by proxy at the Annual Meeting.

According to Southwest Gas’ proxy statement, abstentions and instructions to withhold authority to vote will be treated as Shares that are present and entitled to vote for the purposes of determining whether a quorum exists. Abstentions and instructions to withhold authority will not be counted as votes cast and will have no effect on the outcome of the vote.

Under the rules of the NYSE, when there is a contest with respect to the election of directors, banks, brokerage firms, dealers, trust companies or other custodians may not exercise discretionary voting authority on behalf of the beneficial owners of the Shares on any matters that are to be presented at the Annual Meeting, including matters that are viewed as routine matters. Accordingly, Shares that are held by banks, brokerage firms, dealers, trust companies or other custodians for which no instructions have been provided, which are often referred to as broker non-votes, will not be counted as present and entitled to vote at the Annual Meeting for the purpose of determining the existence of a quorum. If your Shares are held in the name of your bank, brokerage firm, dealer, trust company or other custodian, we encourage you to provide voting instructions to your bank, brokerage firm, dealer, trust company or other custodian promptly so that your Shares can be counted as present for the purposes of establishing a quorum and voted at the Annual Meeting.

If you are a stockholder of record, you must deliver your vote on the GOLD proxy card, the Company’s proxy card or virtually attend the Annual Meeting in order to be counted in the determination of a quorum.

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If your Shares are held in the name of your bank, brokerage firm, dealer, trust company or other custodian, that party will give you instructions for voting your Shares. If you do not give your voting instructions to your bank, brokerage firm, dealer, trust company or other custodian, it will not be allowed to vote your Shares with respect to the election of directors or any additional proposals which may be presented at the Annual Meeting.

Revocation of Proxies

Stockholders of the Company may revoke their proxies at any time prior to exercise by attending the Annual Meeting and voting in person (although attendance at the Annual Meeting will not by itself constitute revocation of a proxy), by delivering a written notice of revocation, or by signing and delivering a properly completed and

subsequently dated proxy. The revocation may be delivered either to Icahn Partners in care of Harkins Kovler, LLC at the address set forth on the back cover of this Proxy Statement or to Southwest Gas at 8360 S. Durango Drive, Post Office Box 98510, Las Vegas, Nevada 89193-8510, or any other address provided by the Company. Although a revocation is effective if delivered to the Company, we request that either the original or photostatic copies of all revocations be mailed to Icahn Partners in care of Harkins Kovler, LLC at the address set forth on the back cover of this Proxy Statement so that we will be aware of all revocations and can more accurately determine how many proxies have been received from the holders of record on the Record Date.

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SOLICITATION OF PROXIES; EXPENSES

The solicitation of proxies pursuant to this Proxy Statement is being made by the Participants. Proxies may be solicited through the mail, press releases and other public statements, electronic communications, telephone, fax and in-person meetings. Each of the Icahn Nominees, the other Participants named in this proxy statement, and employees of the Icahn Participants may assist in the solicitation of proxies without any additional remuneration.

The Participants have retained Harkins Kovler, LLC to provide solicitation and advisory services in connection with this solicitation. Harkins Kovler, LLC will be paid a fee not to exceed $680,000 based upon the campaign services provided. In addition, the Participants will reimburse Harkins Kovler, LLC for its reasonable out-of-pocket expenses and will indemnify Harkins Kovler, LLC against certain liabilities and expenses, including certain liabilities under the federal securities laws. Harkins Kovler, LLC will solicit proxies from individuals, banks, brokerage firms, dealers, trust companies, other custodians and other institutional holders. It is anticipated that Harkins Kovler, LLC will employ up to 35 persons to solicit the Company’s stockholders as part of this solicitation. Harkins Kovler, LLC does not believe that any of its directors, officers, employees, affiliates or controlling persons, if any, is a “participant” in this proxy solicitation. The costs related to this proxy solicitation will be borne by the Participants. Costs of this Proxy Solicitation are currently estimated to be approximately $3.25 million. The actual amount could be higher or lower depending on the facts and circumstances arising in connection with the solicitation. We estimate that through the date hereof, the Participants’ expenses in connection with this Proxy Solicitation are approximately $775,000. If successful, the Participants may seek reimbursement of these costs from the Company.

In the event that the Participants decide to seek reimbursement of their expenses, the Participants do not intend to submit the matter to a vote of the Company’s stockholders. The Board would be required to evaluate the requested reimbursement consistent with its fiduciary duties to the Company and its stockholders. Costs related to the solicitation of proxies include expenditures for attorneys, public relations and other advisors, solicitors, printing, advertising, postage, transportation and other costs incidental to the solicitation.

If you have any questions or require any assistance with voting your Shares, please contact our proxy solicitor, Harkins Kovler, LLC: Banks and Brokerage Firms Please Call Collect: +1 (212) 468-5380; All Others Call Toll Free: +1 (800) 326-5997; Email: SWX@harkinskovler.com.

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QUESTIONS AND ANSWERS ABOUT THE PROXY MATERIALS AND THE ANNUAL MEETING

Q: What are you asking Southwest Gas’ stockholders to do?

A: We are asking for support for the election of our ten director candidates, Nora Mead Brownell, Marcie L. Edwards, Andrew W. Evans, H. Russell Frisby, Jr., Walter M. Higgins III, Rina Joshi, Henry P. Linginfelter, Jesse A. Lynn, Ruby Sharma and Andrew J. Teno, to the Board. As described more fully in this Proxy Statement, we believe our director candidates will add valuable perspectives and leadership to the Board. We believe our candidates possess the skills, experience, energy and leadership abilities necessary to contribute to Southwest Gas as well-rounded Board members. Our director candidates will be active and responsible stewards of the trust placed in them by the stockholders and will represent, and will seek the best possible results for, all of Southwest Gas’ stockholders.

Under the proxy rules, we may solicit proxies in support of the Icahn Nominees. This would enable a stockholder who desires to vote for up to a full complement of ten director nominees to use the GOLD proxy card or, if applicable, the GOLD voting instruction form to vote for the Icahn Nominees. The election of all ten of the Icahn Nominees will replace the entire incumbent Board.

We are also asking stockholders to approve the Bylaw Restoration Proposal and the Special Meeting Proposal. The Special Meeting Proposal, if necessary, is intended to provide stockholders a mechanism to exercise their desire to elect and/or seat the Icahn Nominees in the event they are unable to be elected and/or seated as a result of any required regulatory approvals that may be necessary in conjunction with the closing of the Icahn tender offer and seating of the Icahn Nominees, if elected. We believe that a potential timing issue in terms of third party required approvals that may be necessary should not restrict the will of the stockholders and the Special Meeting Proposal is designed to address that timing issue, if it arises. The purpose of the calling of the Special Meeting is to allow you, the Company’s stockholders, to vote on electing and/or seating the Icahn Slate once the requisite regulatory approvals, if any, have been satisfied (rather than requiring stockholders to wait until the Company’s 2023 Annual Meeting to consider the Icahn Slate).

Q: Who are your director candidates?

A: Nora Mead Brownell, Marcie L. Edwards, Andrew W. Evans, H. Russell Frisby, Jr., Walter M. Higgins III, Rina Joshi, Henry P. Linginfelter, Jesse A. Lynn, Ruby Sharma and Andrew J. Teno are highly qualified individuals with significant business experience. The principal occupation and business experience of each of these candidates is described in this Proxy Statement in the section titled “Matters to be Considered at the Annual Meeting—Proposal 1: Election of the Icahn Nominees—Biographical Information About the Icahn Nominees.” We believe that each of our director candidates would be considered independent under the applicable rules of the NYSE and Southwest Gas’ corporate governance guidelines, and none of our director candidates are affiliated with Southwest Gas or any of its subsidiaries. If elected to the Board, our director candidates would owe fiduciary duties to all of Southwest Gas’ stockholders.

Q: Is David Adame an Icahn Nominee?

A: No. Mr. Adame is not an Icahn Nominee. However, Icahn Partners and the Icahn Participants have indicated that if any of the Icahn Nominees are elected to the Board, then the Icahn Nominees plan to seek to add a director from Arizona to the Board. Icahn Partners and the Beneficial Owners believe that Mr. Adame is a strong candidate for this position. As Mr. Adame is not an Icahn Nominee and does not own any Shares, Icahn Partners and the Icahn Participants do not believe Mr. Adame qualifies as a Participant. Notwithstanding the foregoing, Mr. Adame has been included in this proxy statement solely to the extent that he may be deemed to be a Participant.

Q: Who is entitled to vote?

A: Only holders of voting stock at the close of business on the Record Date, March 21, 2022, are entitled to notice of and to vote at the Annual Meeting. Stockholders who sold Shares before the Record Date (or acquire

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them without voting rights after the Record Date) may not vote such Shares. Stockholders of record on the Record Date will retain their voting rights in connection with the Annual Meeting even if they sell such Shares after the Record Date (unless they also transfer their voting rights).

Q: How important is my vote?

A: Your vote is important, no matter how few Shares you own. The Participants urge you to sign, date, and return the enclosed GOLD proxy card or, if applicable, the enclosed GOLD voting instruction form today to elect the Icahn Nominees, to approve the Special Meeting Proposal and to approve the Bylaw Restoration Proposal. The Board will ultimately be comprised of the ten nominees who receive the most votes cast in favor or his or her election at the Annual Meeting. We urge you to vote in favor of the Icahn Nominees.

Q: How do I vote my Shares?

A: Shares held in record name. If your Shares are registered in your own name, please vote today by signing, dating and returning the enclosed GOLD proxy card in the postage-paid envelope provided. Execution and delivery of a proxy by a record holder of Shares will be presumed to be a proxy with respect to all Shares held by such record holder unless the proxy specifies otherwise.

Shares beneficially owned or held in “street” name. If you hold your Shares in “street” name with a bank, brokerage firm, dealer, trust company or other custodian, only that party can exercise the right to vote with respect to the Shares that you beneficially own through such party and only upon receipt of your specific instructions. Accordingly, it is critical that you promptly give instructions to your broker, bank, dealer, trust company or other nominee to vote for the Icahn Nominees, the Bylaws Restoration Proposal and the Special Meeting Proposal. Please follow the instructions to vote provided on the enclosed GOLD voting instruction form. If your broker, bank, dealer, trust company, or other nominee provides for proxy instructions to be delivered to them by telephone or Internet, instructions will be included on the enclosed GOLD voting instruction form. We urge you to confirm in writing your instructions to the person responsible for your account and provide a copy of those instructions by emailing them to SWX@harkinskovler.com or mailing them to Icahn Partners LP, c/o Harkins Kovler, LLC, 3 Columbus Circle, 15^th Floor, New York, NY 10019, so that we will be aware of all instructions given and can attempt to ensure that such instructions are followed.

We urge you not to return any proxy card provided by Southwest Gas. You do not need to (and should not) vote “withhold” on Southwest Gas’ proxy card to vote for the Icahn Nominees. You should not vote for any of Southwest Gas’ director nominees or any other matter on Southwest Gas’ proxy card. If you vote and return both our GOLD proxy card and Southwest Gas’ proxy card, only the latest dated proxy card will be counted.

Q: What is a quorum?

A: A quorum is the minimum number of Shares that must be represented at a duly called meeting of stockholders in person or by proxy in order to legally conduct business at the meeting. According to Southwest Gas’ proxy statement, a quorum requires the presence of the holders of a majority of the Shares entitled to vote represented in person or by proxy at the Annual Meeting. Under the rules of the NYSE, when there is a contest with respect to the election of directors, banks, brokerage firms, dealers, trust companies or other custodians may not exercise discretionary voting authority on behalf of the beneficial owners of the Shares on any matters that are to be presented at the Annual Meeting, including matters that are viewed as routine matters. Accordingly, Shares that are held by banks, brokerage firms, dealers, trust companies or other custodians for which no instructions have been provided, which are often referred to as broker non-votes, will not be counted as present and entitled to vote at the Annual Meeting for the purpose of determining the existence of a quorum. If your Shares are held in the name of your bank, brokerage firm, dealer, trust company or other custodian, we encourage you to provide voting instructions to your bank, brokerage firm, dealer, trust company or other custodian promptly so that your Shares can be counted as present for the purposes of establishing a quorum and voted at the Annual Meeting.

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Q: What should I do if I receive a proxy card from the Company?

A: If you submit a proxy to us by signing and returning the enclosed GOLD proxy card or, if applicable, the enclosed GOLD voting instruction form, do not sign or return the proxy card or, if applicable, voting instruction form solicited by the Company or follow any voting instructions provided by the Company unless you intend to change your vote, because only your latest dated proxy or, if applicable, voting instruction form will be counted.

We recommend that you disregard any proxy card or solicitation materials that may be sent to you by the Company. If you have already voted using the Company’s white proxy card, you have every right to change your vote by completing and mailing the enclosed GOLD proxy card in the enclosed pre-paid envelope. Only the latest dated validly executed proxy or, if applicable, voting instruction form that you submit will be counted; any proxy or, if applicable, voting instruction form may be revoked at any time prior to its exercise at the Annual Meeting by following the instructions below under “Can I change my vote or revoke my proxy?” If you have any questions or require any assistance with voting your Shares, please contact our proxy solicitor, Harkins Kovler, LLC, 3 Columbus Circle, 15^th Floor, New York, NY 10019; Banks and Brokerage Firms Please Call Collect: +1 (212) 468-5380; All Others Call Toll Free: +1 (800) 326-5997; Email: SWX@harkinskovler.com.

Q: Can I change my vote or revoke my proxy?

A: If you are the stockholder of record, you may change your proxy instructions or revoke your proxy at any time before your proxy is voted at the Annual Meeting. Proxies may be revoked by any of the following actions:

If your Shares are held by a bank, brokerage firm, dealer, trust company or other custodian, you should follow the instructions provided by your bank, brokerage firm, dealer, trust company or other custodian to have your Shares voted. If you attend the Annual Meeting and you beneficially own Shares but are not the record owner, your mere attendance at the Annual Meeting WILL NOT be sufficient to revoke your prior vote. You must have written authority from the record owner to vote your Shares held in its name at the meeting. If you have any questions or require any assistance, contact our proxy solicitor, Harkins Kovler, LLC - Banks and Brokerage Firms Please Call Collect: +1 (212) 468-5380; All Others Call Toll Free: +1 (800) 326-5997; Email: SWX@harkinskovler.com.

IF YOU HAVE ALREADY VOTED USING THE COMPANY’S WHITE PROXY CARD, WE URGE YOU TO REVOKE IT BY FOLLOWING THE INSTRUCTIONS ABOVE. Although a revocation is effective if delivered to the Company, we request that either the original or a copy of any revocation be mailed to Icahn Partners LP, c/o Harkins Kovler, LLC, 3 Columbus Circle, 15^th Floor, New York, NY 10019.

Q: What is the deadline for providing a proxy?

A: We urge you to submit your proxy to us or, if applicable, your voting instruction form to your custodian broker or bank as soon as possible. For your proxy to be voted at the Annual Meeting, we must receive it on or prior to the date of the Annual Meeting. The Annual Meeting is scheduled to be held virtually on May 12, 2022. Consult with your custodian bank or broker to ascertain the deadline for submitting voting instructions.                

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Q: Who is making this proxy solicitation?

A: The solicitation of proxies pursuant to this proxy solicitation is being made by the Participants. Proxies may be solicited by mail, facsimile, telephone, telegraph, Internet, virtually and by advertisements. The Participants will solicit proxies from individuals, banks, brokerage firms, dealers, trust companies, other custodians and other institutional holders. The Participants have requested banks, brokerage firms, dealers, trust companies or other custodians to forward all solicitation materials to the beneficial owners of the Shares they hold of record. The Participants will reimburse these record holders for their reasonable out-of-pocket expenses in so doing. It is anticipated that certain regular employees of the Icahn Participants will also participate in the solicitation of proxies. Such employees will receive no additional consideration if they assist in the solicitation of proxies.

Q: Why are you making this proxy solicitation?

A: We believe that Southwest Gas is in critical need of new leadership at the Board level. We are confident that our highly qualified independent director candidates will add valuable perspectives and leadership to the Board. We believe our candidates possess the skills, experience, energy and leadership abilities necessary to contribute to Southwest Gas as well-rounded Board members. Our director candidates will be active and responsible stewards of the trust placed in them by the stockholders.

Q: What is the Icahn tender offer?

A: The “Icahn tender offer” or the “tender offer” as used in this Proxy Statement refers to the tender offer commenced by IEP Utility Holdings LLC, a Delaware limited liability company, for any and all of the outstanding Shares of the Company, including the associated rights issued in connection with the Company’s adoption of the Poison Pill, at a price of $82.50 per Share in cash. This Proxy Statement is not a recommendation, an offer to purchase or a solicitation of an offer to sell Shares. IEP Utility Holdings filed a Tender Offer Statement and related exhibits with the SEC on October 27, 2021. The Company filed a Solicitation/Recommendation Statement with respect to the tender offer with the SEC on November 9, 2021. Stockholders of the Company are strongly advised to read the Tender Offer Statement (including the related exhibits) and the Solicitation/Recommendation Statement, as they may be amended from time to time, because they contain important information that stockholders should consider before making any decision regarding tendering their Shares. The Tender Offer Statement (including the related exhibits) and the Solicitation/recommendation Statement are available at no charge on the SEC’s website at www.sec.gov. The Tender Offer Statement and other documents that are filed by IEP Utility Holdings LLC with the SEC will be made available to all stockholders of the Company free of charge upon request to the information agent for the tender offer. The information agent for the tender offer is Harkins Kovler, LLC, 3 Columbus Circle, 15^th Floor, New York, NY 10019, toll-free telephone: +1 (800) 326-5997, email: swx@harkinskovler.com. For more information regarding the tender offer, see the section entitled “The Icahn Tender Offer” below.

Q: Is the tender offer related to this proxy solicitation?

A: The tender offer has been launched by IEP Utility, which is an affiliate of Icahn Partners LP. Icahn Partners LP, along with the other participants, are seeking proxies pursuant to this Proxy Statement and are conducting this proxy solicitation. IEP Utility, the offeror in the tender offer, has included a condition to the closing of the tender offer that a majority of the Icahn Slate are elected and seated as members of the Board of Directors of the Company at the Annual Meeting or at any subsequently called special meeting for such purpose. We believe that it is necessary to condition the closing of the tender offer on the election of a majority of the Icahn Slate because the incumbent Board is too focused on saving their own jobs and we anticipate that the incumbent Board will continue to keep the Poison Pill and other entrenchment devices at the Company in place, which will prevent the tender offer from closing and the Company’s stockholders from being able to receive a premium for their Shares. If the Poison Pill and other entrenchment devices at the Company continue in place, then the tender offer cannot close and stockholders will be prevented from receiving a premium for their Shares. Accordingly, IEP Utility has conditioned the tender offer on a majority of the Icahn Slate being elected at the Annual Meeting because we believe that the Icahn Nominees despise entrenchment devices and will seek to remove the Poison Pill and other

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entrenchment devices after the meeting so as to allow the Company’s stockholders the choice to tender their Shares into the offer and receive a premium for their Shares upon the closing of the offer. For more information regarding the tender offer, see the section entitled “The Icahn Tender Offer” below.

Q: Where can I find additional information concerning Southwest Gas and the Annual Meeting?

A: Pursuant to Rule 14a-5(c) promulgated under the Exchange Act, we have omitted from this Proxy Statement certain disclosure required by applicable law to be included in Southwest Gas’ proxy statement in connection with the Annual Meeting, including:

Please refer to the Company’s proxy statement for such information. Except as otherwise noted herein, the information in this Proxy Statement concerning the Company has been taken from or is based upon documents and records on file with the SEC and other publicly available information. We take no responsibility for the accuracy or completeness of information contained in Southwest Gas’ proxy statement. Except as otherwise noted herein, the information in this Proxy Statement concerning the Company has been taken from or is based upon documents and records on file with the SEC and other publicly available information.

This Proxy Statement and all other solicitation materials in connection with this proxy solicitation will be available on the Internet, free of charge, on the SEC’s website at https://www.sec.gov.

Q: Who should I call if I have any questions?

A: If you have any questions, require any assistance in voting your Shares, need additional copies of our proxy materials, or have any other questions, please contact our proxy solicitor, Harkins Kovler, LLC, 3 Columbus Circle, 15^th Floor, New York, NY 10019; Banks and Brokerage Firms Please Call Collect: +1 (212) 468-5380; All Others Call Toll Free: +1 (800) 326-5997; Email: SWX@harkinskovler.com.

Conclusion

We urge you to carefully consider the information contained in this Proxy Statement and then support our efforts by signing, dating, and returning the enclosed GOLD proxy card or, if applicable, the enclosed GOLD voting instruction form today to elect the Icahn Nominees, to approve the Bylaw Restoration Proposal and to approve the Special Meeting Proposal.

Thank you for your support,

Icahn Partners LP

March 28, 2022

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FORWARD LOOKING STATEMENTS

This Proxy Statement may include forward-looking statements that reflect the Participants’ current views with respect to future events, trends, plans or objectives. Statements that include the words “anticipate,” “believe,” “estimate,” “expect,” “forecast,” “intend,” “may,” “objective,” “plan,” “position,” “project,” “should,” “strategy,” “will,” “would” or the negative of those terms or other variations of them or comparable terminology are often used to identify forward-looking statements. All forward-looking statements address matters that involve risks and uncertainties, many of which are beyond our control. Accordingly, there are or will be important factors that could cause actual results to differ materially from those indicated in such statements and, therefore, you should not place undue reliance on any such statements. Any forward-looking statements made in this Proxy Statement are qualified in their entirety by these cautionary statements, and there can be no assurance that the actual results or developments anticipated by the Participants will be realized or, even if substantially realized, that they will have the expected consequences to, or effects on, the Company or its business, operations or financial condition. Except to the extent required by applicable law, the Participants undertake no obligation to update publicly or revise any forward-looking statement, whether as a result of new information, future developments or otherwise.

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THE ICAHN TENDER OFFER

The “Icahn tender offer” or the “tender offer” as used in this Proxy Statement refers to the tender offer (the “Offer”) commenced by IEP Utility Holdings LLC, a Delaware limited liability company (“IEP Utility Holdings” or the “Offeror”), for any and all of the outstanding Shares of the Company, including the associated rights issued in connection with the Company’s adoption of the Poison Pill, at a price of $82.50 per Share in cash. THIS PROXY STATEMENT IS NOT A RECOMMENDATION, AN OFFER TO PURCHASE OR A SOLICITATION OF AN OFFER TO SELL SHARES.

The Offer is being made pursuant to the terms and subject to the conditions set forth in the Offer to Purchase, dated October 27, 2021 (the “Offer to Purchase”), the related letter of transmittal (the “Letter of Transmittal”), the Notice of Guaranteed Delivery (the “Notice of Guaranteed Delivery”), and the Supplement to the Offer, dated December 7, 2021 (the “Supplement to the Offer”), which together with the Offer to Purchase, the Letter of Transmittal, Notice of Guaranteed Delivery, and the other related materials, as each may be amended or supplemented from time to time, constitutes the “Offer”. All references to the Offer to Purchase shall be deemed to refer to the Offer to Purchase, dated October 27, 2021, as supplemented by the Supplement to the Offer, and otherwise supplemented, amended and modified to date. The references to “we”, “our” and “us” in this section regarding the Icahn Tender Offer refer to IEP Utility Holdings, the Offeror in the Offer.

The following summary of the terms of the Offer is being provided to the Company’s stockholders in this Proxy Statement for their reference. We urge you to review the Tender Offer Statement and related exhibits that were filed by IEP Utility Holdings with the SEC on October 27, 2021, and the Solicitation/Recommendation Statement with respect to the Offer filed by the Company with the SEC on November 9, 2021, as they may be amended from time to time, because they contain important information that the Company’s stockholders should consider before making any decision regarding tendering their Shares.

Conditions to the Offer

The Offer is conditioned on, among other things: (i) the Rights Agreement has been validly terminated or the Rights have been redeemed and are otherwise inapplicable to the Offer (the “Poison Pill Condition”); (ii) the Company’s board of directors has waived the applicability of Article 7(A) of the Company’s Certificate of Incorporation to the purchase of the Shares by the Offeror in the Offer (the “Article 7A Condition”); (iii) the

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Company has not issued, and has not authorized or proposed the issuance of, any equity securities or equity-linked securities, subject to certain ordinary course exceptions, other than pursuant to a rights offering that treats all stockholders equally (the “Equity Condition”); and (iv) a majority of the members of the Icahn Slate are elected and seated as members of the board of directors of the Company at the Southwest Gas 2022 Annual Meeting or at any subsequently called special meeting for such purpose (the “Board Condition”).

Notwithstanding any other provision of the Offer, and in addition to (and not in limitation of) the Offeror’s rights to extend and amend the Offer, the Offeror shall not be required to accept for payment or pay for any Shares tendered pursuant to the Offer, and may terminate or amend the Offer and may postpone the acceptance for payment of and payment for, Shares tendered, if (i) any one or more of the Poison Pill Condition, the Article 7(A) Condition, the Equity Condition or the Board Condition is not satisfied or waived prior to the expiration of the Offer, or (ii) if at any time prior to the expiration of the Offer any of the following conditions shall occur:

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For purposes of the Offer, “Burdensome Condition” means: (a) any agreement, consent, action, condition, restriction, or other mitigation involving the Company or any of its subsidiaries that would be, or would reasonably be expected to be, individually or in the aggregate, materially adverse to the businesses, assets or financial condition of the Company and its subsidiaries, taken as a whole; or (b) any proffer, consent or agreement by the Offeror or any of its affiliates, including Carl C. Icahn, to (i) prohibit or limit their or his ownership of any portion of their or his respective businesses or assets (without giving effect to the consummation of the Offer), (ii) divest, hold, separate or otherwise dispose of any portion of their or his respective businesses or assets (without giving effect to the consummation of the Offer), or (iii) impose any other limitation on their or his ability to effectively control or operate their or his respective businesses or otherwise affect their or his ability to control their respective operations (without giving effect to the consummation of the Offer).

If, on the Expiration Date, any or all of the Offer Conditions have not been satisfied or waived, the Offeror reserves the right, subject to complying with applicable federal securities laws and the rules and regulations of the SEC thereunder (the “Securities Laws”) and the rules and regulations of the NYSE, to: (i) decline to purchase any of the Shares tendered, terminate the Offer and return all tendered Shares to tendering stockholders; (ii) waive any of the Offer Conditions (subject to the terms of Section 14 of the Offer to Purchase) and purchase all Shares validly tendered; (iii) extend the Offer and, subject to the right of stockholders to withdraw Shares until the Expiration Date, retain the Shares that have been tendered during the period or periods for which the Offer is extended (which may delay acceptance for payment of, and the payment for, any Shares); and (iv) amend the Offer, including by increasing the consideration offered, in each case, by giving oral or written notice of such waiver, extension or amendment to the Depositary and making a public announcement thereof. In addition, the Offeror may extend the Offer for any period required by the Securities Laws or the staff of the SEC or as required by applicable law. If any of the conditions to the Offer becomes incapable of being satisfied and such condition may not be waived by the Offeror, then the Offer will not be able to be completed

Trust Structure

In connection with the closing of the Offer, as needed, the Offeror will enter into one or more trust agreements (each, a “Trust Agreement” and collectively, the “Trust Agreements”) with independent third-party trustees to form one or more statutory trusts under Delaware law (each, a “Trust” and collectively, the “Trusts”). Upon the closing of the Offer, if Shares are tendered that would result in the Offeror and its affiliates holding more than 24.9% of the Shares, then all Shares in excess of 24.9% will be transferred to one or more independent Trusts with each Trust being independent of the other trusts and not owning more than 24.9% of all the Shares. The Trust will be the record owner of the Shares transferred to the Trust and will be subject to instructions in the Trust Agreement governing the Trust. The Trust Agreements will require that the trustee for each Trust vote the Shares held in such Trust in the independent trustee’s sole and absolute discretion without consultation with the Offeror and its affiliates.

By way of example, if 20% or fewer of the Shares are tendered into the Offer, then the Offeror would accept such Shares and would not place any Shares into the Trusts as the Offeror would own an aggregate of 24.9% of the Shares when adding the 20% of the Shares acquired in the Offer with the 4.9% of the Shares that the Offeror’s affiliates currently own. However, if 60% of the Shares are tendered into the Offer, the Offeror would retain full ownership and control including voting control of 24.9% of the Shares (comprised of 20% of the Shares acquired in the Offer plus the 4.9% of the Shares that the Offeror’s affiliates currently own), and the remaining tendered shares would be deposited to two Trusts that will collectively own and hold the remaining 40% of the Shares (with neither Trust holding more than 24.9% of the Shares). Effectively, this means that the Offeror and its affiliates will be limited to owning, holding and voting the Shares in an amount equal to 24.9% of the Shares (that includes the 4.9% of Shares currently owned by the Offeror’s affiliates), and any Shares that are tendered into the Offer in excess of the 24.9% threshold will be owned beneficially by one or more Trusts and voted by the trustees thereof, pursuant to the terms of each Trust Agreements, as described below. While the Offeror will be a beneficiary of such Trusts, the actual record ownership of the Shares will be held by the Trusts and voting of the Shares in such Trusts shall be in accordance with the Trust Agreement as outlined below.

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Each Trust will be governed by Delaware law and the Trust Agreements entered into between the Offeror (or one of its affiliates) and the trustee for each of the Trusts. Each Trust Agreement will provide the terms on which the relevant Trust will own, hold and vote the Shares held in such Trust. The Trust Agreements will require that the trustee for each Trust vote the Shares held in such Trust in the independent trustee’s sole and absolute discretion without consultation with the Offeror and its affiliates. Accordingly, the trustee of each Trust will have sole voting power with respect to the Shares held in such Trust. Although the Offeror (or one of its affiliates) will be the beneficiary of each Trust, neither the Offeror nor its affiliates will be able to exercise control over the Shares held in Trust. Should the Offeror ever decide to exercise any voting rights, direction or control over the Shares in the Trusts, the Offeror will be required to file all required applications with any local, state or federal agencies having any jurisdiction over the matter for approval for the exercise of any of such rights or control and shall not be permitted to exercise any of such rights unless or until such approval is obtained (except as provided below). Upon receipt of any necessary regulatory approvals, the Shares held in the Trusts would be transferred to the Offeror or one of its affiliates.

Except for a transfer to the Offeror or one of its affiliates upon receipt of all required regulatory approvals, the Trust Agreements will prohibit the sale, transfer or other disposition of the Shares owned by the Trust until the earlier of: (i) any required regulatory approval is denied or any applicable regulatory authority has indicated that such approval will be denied; (ii) any required regulatory approval is subject to the imposition of conditions that the Offeror (or its affiliate), by written notice to the trustees, has deemed to be unacceptable or any applicable regulatory authority has indicated that such approval will be subject to the imposition of conditions that the Offeror (or its affiliate), by written notice to the trustees, has deemed to be unacceptable, and (iii) two years from the date on which the Shares are placed in the Trusts. The Trust Agreement will also require that Shares may only be sold, transferred or disposed of in open market transactions with third parties who are not affiliated with the Offeror and no single transaction (or series of related transactions) may involve the sale of more than 24.9% of the Shares to any single third party or group of related parties. As a result of these Trust Agreements, the Offeror (and its affiliates) will not control more than 24.9% of the voting power of the Company. The Trusts and the Trust Agreements will not govern the voting or disposition of any Shares that are held by the Offeror (or its affiliates) directly (it being understood that the amount of such Shares will not exceed 24.9% of the overall voting power of the Company).

The Trusts and the Trust Agreements, which will limit the number of Shares that the Offeror and its affiliates are entitled to vote to a maximum of 24.9% of the Shares, allow the Offeror to close the Offer and accept all Shares that are validly tendered and not withdrawn in the Offer, without first obtaining regulatory approvals that may have otherwise been required if the closing of the Offer would have resulted in the Offeror obtaining voting power or control in excess of 24.9% of the Shares.

A form of the Trust Agreement expected to be entered into by the Offeror or one of its affiliates in connection with the closing of the Offer is attached as an exhibit to the Offer to Purchase.

Regulatory Approvals

The Offeror has amended the terms of the Offer to remove the receipt of any required governmental or regulatory approvals which, in each case, have not been appealed and are no longer appealable, and do not impose any Burdensome Conditions (which we referred to as the “Regulatory Approval Condition”) as a condition to the closing of the Offer. Upon the closing of the Offer, if Shares are tendered that would result in the Offeror (and its affiliates) holding more than 24.9% of the Shares, then all of the Shares in excess of 24.9% will be transferred to one or more independent Delaware statutory trusts with each trust being independent of the other trusts and not owning more than 24.9% of all Shares. The trust agreements, which will limit the number of Shares that the Offeror (and its affiliates) are entitled to vote to a maximum of 24.9% of the Shares, allow the Offeror to close the Offer and accept all Shares that are validly tendered and not withdrawn in the Offer, without first obtaining regulatory approvals that may have otherwise been required if the closing of the Offer would result in the Offeror obtaining voting power or control in excess of 24.9% of the Shares. In light of the foregoing, the Offeror has

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removed the Regulatory Approval Condition to the Offer. Accordingly, the descriptions of the regulatory approvals, which may be required in certain circumstances after the closing of the Offer, in Arizona, California and Nevada that are included below are for informational purposes only as the Offer is not conditioned upon receipt of any such approvals.

HSR Act

On November 1, 2021, the waiting period under the HSR Act expired with respect to the Offer.

General – No Approvals Required from Arizona, California or Nevada Prior to Closing

In general, the states of Arizona, California and Nevada have regulations that apply to the change of control of a public utility or regulated utility that falls under the jurisdiction of each such state. Southwest Gas Corporation, a subsidiary of Southwest Gas, is a public or regulated utility that operates in each of Arizona, California and Nevada. Accordingly, the rules and regulations of these states may be applicable to the Offer. As discussed more fully below, of the three states, Nevada has the lowest ownership threshold, which is the transfer of 25% of the common stock of a regulated utility company, that triggers review and approval of the Public Utilities Commission of Nevada. For Arizona and California, the threshold at which the Arizona Corporation Commission or the California Public Utilities Commission, as applicable, is required to review the transaction is closer to 50% or more of the voting stock of an entity that directly or indirectly controls a public utility. The specific rules and regulations of each of these states that may be applicable to the Offer are more fully described below.

Due to the uncertainty regarding the number of Shares that the Offeror may ultimately own following the closing of the Offer, the Offeror has decided to limit the number of Shares that it will take ownership over and control following the closing of the Offer such that the Offeror (and its affiliates) will not control more than 24.9% of the voting power of the Company. Upon the closing of the Offer, the Offeror will be limited to owning 24.9% of the Shares of the Company (that will include the 4.9% of the Shares that are currently owned by affiliates of the Offeror) and all Shares tendered in excess of such threshold will be placed into one or more Trusts and held by such Trust(s) pursuant to the terms of the Trust Agreements with independent third-party trustees. Upon the closing of the Offer, if Shares are tendered that would result in the Offeror and its affiliates holding more than 24.9% of the Shares, then all Shares in excess of 24.9% will be transferred to one or more independent Trusts with each Trust being independent of the other trusts and not owning more than 24.9% of all the Shares. As a result of these Trusts, the Offeror (and its affiliates) will not control more than 24.9% of the voting power of the Company no matter how many Shares are tendered into the Offer such that regulatory approval thresholds in Arizona, California and Nevada will not be triggered at the closing of the Offer. Accordingly, there are currently no outstanding required regulatory approvals that must be satisfied prior to the closing of the Offer.

Arizona

Under Arizona law, the organization or “reorganization” of an entity that directly or indirectly controls a public utility is subject to review by the Arizona Corporation Commission (the “ACC”) under the ACC’s Public Utilities Holding Companies and Affiliated Interests Rules (“ACC Rules”). Under the ACC Rules, a “reorganization” includes the “acquisition or divestiture of a financial interest” in an entity that controls a public utility, the merger of an entity that controls a public utility or the reconfiguration of the corporate structure that affects the position of the public utility in the corporate structure. “Control” is considered to be the “power to direct the management policies of an entity” that directly or indirectly controls a public utility, “whether through ownership of voting securities, or by contract, or otherwise.” ACC Decision No. 58063 (November 3, 1992) identified six situations where the ACC will review a potential organization or “reorganization” of public utility holding company. The acquisition or transfer of more than 50% of the common stock of a public utility holding company would likely be considered to be an organization or reorganization of a public utility holding company subject to ACC review. Therefore, because Southwest Gas Holdings is a public utility holding company, the acquisition or transfer of more than 50% of the issued and outstanding Shares would be subject to oversight by the ACC.

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California

In California, an authorization from the California Public Utilities Commission (the “CPUC”) is required before an entity may acquire or control either directly or indirectly any California public utility. Southwest Gas Corporation, a subsidiary of Southwest Gas, is a public utility that is regulated by the CPUC. The CPUC assesses each application on a case-by-case basis. Past decisions have indicated that holding an interest under 30 percent alone would not trigger required approval and that the California Corporations Code definition of “control” at 50 percent is guiding. Under the Public Utilities Code, transactions involving the acquisition or control of a public utility that has gross annual California revenue in excess of $500 million are subject to a different standard of review than transactions involving the acquisition or control of a public utility that has gross annual California revenue of less than $500 million. Southwest Gas Corporation’s California revenues for 2021 were less than $500 million.

Nevada

Under Nevada law, any transaction of a regulated entity or holding company owning or controlling a regulated utility company in which not more than 25% of the common stock is transferred is subject to the review and approval of the Public Utilities Commission of Nevada (the “PUCN”). Southwest Gas is a holding company that owns and controls a regulated utility company operating in Nevada such that the acquisition or transfer of more than 25% of the Shares would be subject to the review and approval of the PUCN.

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QUESTIONS AND ANSWERS ABOUT THE OFFER

WHO IS OFFERING TO BUY MY SECURITIES IN THE OFFER?

IEP Utility Holdings LLC, a Delaware limited liability company (the “Offeror”), is offering to buy your securities. The Offeror is a wholly-owned subsidiary of Icahn Enterprises Holdings L.P., a Delaware limited partnership (“Icahn Enterprises Holdings”). The Offeror is the sole bidder in the Offer. However, due to their relationship to the Offeror, the following persons may be deemed to be Offering Persons in connection with the Offer: Icahn Enterprises Holdings, Icahn Enterprises L.P., Icahn Enterprises G.P. Inc., Beckton Corp. and Carl C. Icahn. The Offeror is affiliated with Carl C. Icahn. Certain other entities affiliated with Mr. Icahn beneficially own an aggregate of approximately 4.8% of the issued and outstanding Shares. The Offeror was formed for the purpose of acquiring all of the issued and outstanding Shares. See the “Introduction” to the Offer to Purchase and Section 8 of the Offer to Purchase — “CERTAIN INFORMATION CONCERNING THE OFFEROR”.

WHAT ARE THE CLASSES AND AMOUNTS OF SECURITIES SOUGHT IN THE OFFER?

The Offeror is offering to purchase any and all of the issued and outstanding Shares. Each Share is comprised of one share of Common Stock, par value $1.00 per share, of Southwest Gas Holdings, Inc., a Delaware corporation (“Southwest Gas” or the “Company”), together with one associated Right issued pursuant to the Rights Agreement. See the “Introduction” and Section 1 of the Offer to Purchase — “TERMS OF THE OFFER”.

WHAT ARE THE ASSOCIATED RIGHTS?

The associated rights are Rights issued pursuant to the Rights Agreement, dated October 10, 2021, between Southwest Gas and Equiniti Trust Company, as Rights Agent, that are issued and outstanding. The Rights were issued to all of the Company’s stockholders, but currently are not represented by separate certificates. A tender of the Shares will include a tender of both the shares of Common Stock and the associated Rights, unless certificates representing the Rights are issued as provided in the Rights Agreement prior to the completion of the Offering.

WHAT ARE YOUR PURPOSES FOR THE OFFER AND PLANS FOR THE COMPANY AFTER THE OFFER IS COMPLETED?

The purpose of the Offer is for Icahn Enterprises L.P., through the Offeror, to provide immediate liquidity at a premium for those stockholders choosing to tender their Shares, while also providing the opportunity for those stockholders who, like us, believe in the long-term prospects of the Company — under proper management — to realize its potential upside.

If the Offer is completed, the Offeror will be able to acquire up to 24.9% of the Shares tendered into the Offer directly, with any additional Shares to be placed in the Trusts and held pursuant to the Trust Agreements. If a majority of the issued and outstanding Shares are tendered into the Offer, at the time of the closing of the Offer, the Offeror (and its affiliates) will be limited to holding and controlling 24.9% of the Shares with any Shares in excess of 24.9% to be placed into the Trusts, and the Offeror may only obtain control of such Shares following the receipt of any required regulatory approvals following the closing of the Offer.

Ultimately, the Offeror intends to seek to obtain the required regulatory approvals following the closing of the Offer and, following the receipt of such approvals, to transfer any Shares held in the Trust(s) to the Offeror (or one of its affiliates).

If, and to the extent that, the Offeror (and its affiliates) acquires control of the Company following the closing of the Offer and the receipt of any required regulatory approvals, the Offeror intends to conduct a detailed review, subject to applicable law, of the Company and its assets, corporate structure, capitalization, operations, properties, policies, management and personnel and consider and determine what, if any, changes would be

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desirable in light of the circumstances which then exist, which may include selling all or any portion of the Shares acquired by the Offeror and its affiliates in the Offer. The Offeror’s strategic plans for the Company include (i) simplifying the organizational structure and optimizing the Company’s regulated utility, (ii) decreasing general and administrative expenses and eliminating inappropriate expenses, (iii) improving credit ratings and strengthening the Company’s balance sheet, (iv) focusing on renewable gas and green hydrogen initiatives, (v) seeking to recover costs associated with the replacement of faulty pipe, including the Driscopipe^® 8000, and (vi) seeking best-in-class management for the Company. See Section 11 of the Offer to Purchase — “PURPOSE OF THE OFFER; PLANS FOR THE COMPANY”.

The Offer is conditioned on, among other things: (i) the Rights Agreement has been validly terminated or the Rights have been redeemed and are otherwise inapplicable to the Offer; (ii) the Company’s board of directors has waived the applicability of Article 7(A) of the Company’s Certificate of Incorporation to the purchase of the Shares by the Offeror in the Offer; (iii) the Company has not issued, and has not authorized or proposed the issuance of, any equity securities or equity-linked securities, subject to certain ordinary course exceptions, other than pursuant to a rights offering that treats all stockholders equally; and (iv) a majority of the members of the Icahn Slate are elected and seated as members of the board of directors of the Company at the Southwest Gas 2022 Annual Meeting or at any subsequently called special meeting for such purpose. See Section 11 of the Offer to Purchase — “PURPOSE OF THE OFFER; PLANS FOR THE COMPANY” and Section 14 of the Offer to Purchase — “CONDITIONS OF THE OFFER”.

HOW MUCH ARE YOU OFFERING TO PAY, AND WHAT IS THE FORM OF PAYMENT?

We are offering to pay $82.50 per Share, without interest, net in cash, but subject to any withholding of taxes, for each Share tendered and accepted for payment in the Offer. See the “Introduction” and Section 11 of the Offer to Purchase — “PURPOSE OF THE OFFER; PLANS FOR THE COMPANY”.

IS THERE AN AGREEMENT GOVERNING THE OFFER?

No, there is no agreement governing the Offer.

WHAT IS THE MARKET VALUE OF MY SHARES AS OF A RECENT DATE?

On October 4, 2021, the last full trading day before the first public announcement of a proposal by Southwest Gas to acquire Questar Pipelines from Dominion Energy, Inc., the closing price of Southwest Gas’s Common Stock reported on the New York Stock Exchange (the “NYSE”) was $66.07 per Share. On October 13, 2021, the last full trading day before the Offeror publicly announced its intention to commence the Offer, the closing price of Southwest Gas’s Common Stock reported on the NYSE was $64.92 per Share. On October 26, 2021, the last full trading day before commencement of the Offer, the closing price of Southwest Gas’s Common Stock reported on the NYSE was $69.16 per Share. On March 11, 2022, the last full trading day before the announcement of the increase in the Offer Price, the closing price of Southwest Gas’s Common Stock reported on the NYSE was $72.59 per Share. On March 25, 2022, the last full trading day before the filing of this Proxy Statement, the closing price of Southwest Gas’s Common Stock reported on the NYSE was $79.09 per Share. See Section 6 of the Offer to Purchase — “PRICE RANGE OF THE SHARES; DIVIDENDS”.

WILL I HAVE TO PAY ANY FEES OR COMMISSIONS IF I TENDER MY SHARES INTO THE OFFER?

If you are the record owner of your Shares at the closing of the Offer and you tender your Shares to the Offeror in the Offer, you will not have to pay brokerage fees or similar expenses. If you own your Shares through a bank, broker or other nominee, and your bank, broker or other nominee tenders your Shares on your behalf, your bank, broker or other nominee may charge you a fee for doing so. You should consult your bank, broker or other nominee to determine whether any charges will apply. See the “Introduction” to the Offer to Purchase.

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WHAT DOES THE BOARD OF DIRECTORS OF SOUTHWEST GAS THINK OF THE OFFER?

According to the Solicitation/Recommendation Statement under Section 14(d)(4) of the Exchange Act (the “Schedule 14D-9”), the Company amazingly indicated that, notwithstanding the Company’s recent sales of Shares at prices as low as $68.00 per Share under the Company’s at-the-market sales program, its board of directors reviewed the Offer and nevertheless determined that our Offer Price is inadequate, undervalues the Company and is not in the best interests of the Company and its stockholders. Based on the Schedule 14D-9, the Company’s board of directors unanimously recommends that the holders of the Shares reject the Offer and not tender any Shares pursuant to the Offer. On March 14, 2022, the Offeror announced that it was increasing the Offer Price to be paid in the tender offer to $82.50 per Share, which represents a 10% increase over the initial offer price of $75.00 per Share. As of March 27, 2022, the Company had not responded to, nor has it provided a recommendation with respect to, the increased Offer Price of $82.50. Accordingly, the discussion above relates to the Company’s recommendation regarding the initial offer price of $75.00 per Share as we do not know the Company’s recommendation with respect to the increased offer price of $82.50 per Share.

The Southwest Gas board of directors has refused to discuss the Offer with us. In light of the unwillingness of the Southwest Gas board of directors to engage with us with respect to a negotiated transaction and its public statements with respect to our prior proposals, we are making the offer directly to Southwest Gas stockholders on the terms and conditions set forth in the Offer to Purchase.

The Offeror strongly disagrees with the Company’s conclusions regarding the Offer, including the Company’s characterization of the terms of the Offer as set forth in the Schedule 14D-9. See Section 11 of the Offer to Purchase — “PURPOSE OF THE OFFER; PLANS FOR THE COMPANY” of the Offer to Purchase for additional information regarding the Offeror’s reasons for the Offer.

DO YOU HAVE THE FINANCIAL RESOURCES TO MAKE PAYMENT?

Yes. We and our parent, Icahn Enterprises Holdings, are able to provide 100% of the funds required to pay for the Shares tendered from our cash, cash equivalents and from our ability to realize cash upon the sale of liquid securities. See Section 9 of the Offer to Purchase — “SOURCE AND AMOUNT OF FUNDS”.

IS YOUR FINANCIAL CONDITION RELEVANT TO MY DECISION TO TENDER IN THE OFFER?

We do not think our financial condition is relevant to your decision whether to tender in the Offer because the form of payment consists solely of cash and we have all of the financial resources necessary to complete the Offer. The Offer is not conditioned upon the Offeror obtaining financing. See Section 9 of the Offer to Purchase — “SOURCE AND AMOUNT OF FUNDS”.

IS THERE ANY MINIMUM TENDER CONDITION TO THE OFFER?

No. There is no condition to the Offer requiring a minimum number of Shares to be tendered in the Offer. We will purchase any and all Shares that are validly tendered in the Offer and not properly withdrawn subject to the satisfaction of the conditions of the Offer. See Section 14 of the Offer to Purchase — “CONDITIONS OF THE OFFER”.

WHAT ARE THE MOST SIGNIFICANT CONDITIONS OF THE OFFER?

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The Offer is also subject to other customary conditions. The Offer is not conditioned upon our obtaining financing, any due diligence review of the Company or any minimum number of Shares being tendered. See Section 14 of the Offer to Purchase — “CONDITIONS OF THE OFFER”.

The conditions of the Offer must be satisfied on or prior to the Expiration Date.

IF I DECIDE NOT TO TENDER, HOW WILL THE OFFER AFFECT MY SHARES?

If the conditions of the Offer as set forth in Section 14 of the Offer to Purchase — “CONDITIONS OF THE OFFER” are satisfied or waived and we complete the Offer, the number of stockholders and the number of Shares that are held by the public will be reduced and such number of stockholders and such number of Shares may be so small that there may no longer be an active public trading market (or, possibly, there may not be any public trading market) for the Shares. Also, it is possible that Southwest Gas may no longer be required to make filings with the SEC or otherwise comply with the rules of the SEC relating to publicly held companies on account of its equity interests.

If we complete the Offer, the Offeror will be able to acquire up to 24.9% of the Shares tendered into the Offer directly, with any additional Shares to be placed in the Trusts and held pursuant to the Trust Agreements. If a majority of the issued and outstanding Shares are tendered into the Offer, at the time of the closing of the Offer, the Offeror (and its affiliates) will be limited to holding and controlling 24.9% of the Shares with any Shares in excess of 24.9% to be placed into the Trusts, and the Offeror may only obtain control of such Shares following the receipt of any required regulatory approvals following the closing of the Offer.

Ultimately, the Offeror intends to seek to obtain the required regulatory approvals following the closing of the Offer and, following the receipt of such approvals, to transfer any Shares held in the Trust(s) to the Offeror (or one of its affiliates).

If, and to the extent that, the Offeror (and its affiliates) acquires control of the Company following the closing of the Offer and the receipt of any required regulatory approvals, the Offeror intends to conduct a detailed review, subject to applicable law, of the Company and its assets, corporate structure, capitalization, operations, properties, policies, management and personnel and consider and determine what, if any, changes would be

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desirable in light of the circumstances which then exist, which may include selling all or any portion of the Shares acquired by the Offeror and its affiliates in the Offer. The Offeror’s strategic plans for the Company include (i) simplifying the organizational structure and optimizing the Company’s regulated utility, (ii) decreasing general and administrative expenses and eliminating inappropriate expenses, (iii) improving credit ratings and strengthening the Company’s balance sheet, (iv) focusing on renewable gas and green hydrogen initiatives, (v) seeking to recover costs associated with the replacement of faulty pipe, including the Driscopipe^® 8000, and (vi) seeking best-in-class management for the Company.

See the “Introduction” and Section 12 of the Offer to Purchase — “CERTAIN EFFECTS OF THE OFFER”.

IF I TENDER MY SHARES, WHEN AND HOW WILL I GET PAID?

If the conditions of the Offer as set forth in Section 14 of the Offer to Purchase — “CONDITIONS OF THE OFFER” are satisfied or waived and we complete the Offer and accept your Shares for payment, we will pay you an amount equal to the number of Shares you tendered multiplied by $82.50 in cash, without interest, less any applicable withholding taxes promptly following expiration of the Offer. See Section 1 of the Offer to Purchase — “TERMS OF THE OFFER” and Section 4 of the Offer to Purchase — “ACCEPTANCE FOR PAYMENT AND PAYMENT OF SHARES”.

HOW LONG DO I HAVE TO DECIDE WHETHER TO TENDER IN THE OFFER?

Unless we extend the Expiration Date of the Offer, you will have until 12:00 midnight, New York City time, on Thursday, April 21, 2022, unless the Offer is extended or earlier terminated in the event that a condition to the Offer is incapable of being satisfied, to tender your Shares in the Offer. If you cannot deliver everything that is required to tender your Shares by that time, you may be able to use a guaranteed delivery procedure, which is described later in the Offer to Purchase. See Section 1 of the Offer to Purchase — “TERMS OF THE OFFER” and Section 2 of the Offer to Purchase — “PROCEDURE FOR ACCEPTING THE OFFER AND TENDERING SHARES”.

CAN THE OFFER BE EXTENDED AND UNDER WHAT CIRCUMSTANCES?

We can extend the Offer from time to time and for any reason. We may extend the offer in the following circumstances:

See Section 1 of the Offer to Purchase — “TERMS OF THE OFFER”.

WHEN WOULD THE OFFEROR DECIDE NOT TO EXTEND THE OFFER?

The Offeror does not expect to extend the Offer if one of the conditions of the Offer becomes incapable of being satisfied.

DOES THE COMPANY CONTROL ANY OF THE CONDITIONS OF THE OFFER?

Yes. The Company has the ability to satisfy certain conditions of the Offer, including the Poison Pill Condition and the Article 7(A) Condition. In addition, the Company controls whether or not the Equity Condition is

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satisfied. If the Company choses to issue any equity securities or equity-linked securities and does not allow the Company’s stockholders to participate pro rata in such issuance, then the Company will cause the Equity Condition to not be capable of being satisfied and thereby depriving the Company’s stockholders with the ability to participate in the Offer. See Section 11 of the Offer to Purchase — “PURPOSE OF THE OFFER; PLANS FOR THE COMPANY”.

WILL YOU PROVIDE A SUBSEQUENT OFFERING PERIOD?

We may elect to provide a “subsequent offering period” in accordance with Rule 14d-11 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). A subsequent offering period, if one is included, will be an additional period of time beginning after we have purchased Shares tendered during the Offer, during which stockholders may tender, but not withdraw, their Shares and receive the Offer Price. We do not currently intend to include a subsequent offering period, although we reserve the right to do so. See Section 1 of the Offer to Purchase — “TERMS OF THE OFFER”.

HOW WILL I BE NOTIFIED IF THE OFFER IS EXTENDED OR IF A SUBSEQUENT OFFERING PERIOD IS PROVIDED?

If we extend the Offer or provide a subsequent offering period, we will inform Continental Stock Transfer & Trust Company (which is the Depositary for the Offer) of that fact and will make a public announcement, not later than 9:00 a.m., New York City time, on the next business day after the day on which the Offer was scheduled to expire. See Section 1 of the Offer to Purchase — “TERMS OF THE OFFER”.

ARE THERE ANY CONSEQUENCES OF THE OFFER ON ANY MATERIAL CONTRACTS OF THE COMPANY OF WHICH I SHOULD BE AWARE?

Certain of the material contracts that the Company has filed with the SEC as exhibits to its Form 10-K for the year ended December 31, 2021, contain provisions that may be triggered upon a “change of control” of the Company as such term is defined in the applicable underlying material contract.

On January 14, 2022, the Company announced that its Board of Directors adopted a board resolution designating the Icahn Nominees, should such slate of directors be elected by the Company’s stockholders at the Annual Meeting, as “continuing directors” for the sole purposes of ensuring that the “change in control” provisions in the Company’s debt documents not be triggered by the nomination (or election) of any member or members of the Icahn Slate at the Annual Meeting. Based on this statement from the Company, we do not believe that these “change in control” provisions will be triggered by the election and seating of the Icahn Slate at the Annual Meeting.

The determination as to whether these provisions are triggered by the closing of the Offer will depend on whether the number of Shares that are ultimately tendered in the Offer is considered a “change in control” under the applicable material contract. While the closing of the Offer may trigger these provisions, the Offer is not conditioned upon obtaining any approvals, consents or waivers with respect to these material contracts. See Section 11 — “PURPOSE OF THE OFFER; PLANS FOR THE COMPANY” and Section 12 — “CERTAIN EFFECTS OF THE OFFER”.

WHAT ARE THE TRUSTS AND WHEN WILL THEY BE FORMED?

Upon the closing of the Offer, if Shares are tendered that would result in the Offeror and its affiliates holding more than 24.9% of the Shares, then all Shares in excess of 24.9% will be transferred to one or more statutory trusts under Delaware law (each, a “Trust” and collectively, the “Trusts”) with each Trust being independent of the other trusts and not owning more than 24.9% of all the Shares. In connection with the closing of the Offer, as needed, the Offeror will enter into one or more trust agreements (each, a “Trust Agreement” and collectively, the “Trust Agreements”) with independent third-party trustees relating to such Trusts.

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Each Trust will be the record owner of the Shares transferred to such Trust and will be subject to instructions in the Trust Agreement governing the Trust. The Trust Agreements will require that the trustee for each Trust vote the Shares held in such Trust in the independent trustee’s sole and absolute discretion without consultation with the Offeror and its affiliates. The Trusts and the Trust Agreements remove the requirement for the Offeror to obtain regulatory approvals (to the extent that such approvals are necessary) prior to the closing of the Offer and are intended to be in place for a limited period of time. The process for obtaining any required regulatory approvals would occur after the closing of the Offer. Except for a transfer to the Offeror or one of its affiliates upon receipt of all required regulatory approvals, the Trust Agreements will prohibit the sale, transfer or other disposition of the Shares owned by the Trust until the earlier of: (i) any required regulatory approval is denied or any applicable regulatory authority has indicated that such approval will be denied; (ii) any required regulatory approval is subject to the imposition of conditions that the Offeror (or its affiliate), by written notice to the trustees, has deemed to be unacceptable or any applicable regulatory authority has indicated that such approval will be subject to the imposition of conditions that the Offeror (or its affiliate), by written notice to the trustees, has deemed to be unacceptable, and (iii) two years from the date on which the Shares are placed in the Trusts.

IS IT POSSIBLE THAT NO TRUSTS WILL BE FORMED?

Yes. If 20% or fewer Shares are tendered into the Offer, then the Offeror would accept such Shares and would not place any Shares into the Trusts as the Offeror would own an aggregate of 24.9% of the Shares when adding the 20% of the Shares acquired in the Offer with the 4.9% of the Shares that the Offeror’s affiliates currently own.

WHY ARE THE TRUSTS BEING FORMED?

The Trusts and the Trust Agreements, which will limit the number of Shares that the Offeror and its affiliates are entitled to vote to a maximum of 24.9% of the Shares, allow the Offeror to close the Offer and accept all Shares that are validly tendered and not withdrawn in the Offer, without first obtaining regulatory approvals that may have otherwise been required if the Offeror would have obtained voting power or control in excess of 24.9% of the Shares as a result of the closing of the Offer. The Trust would be formed, if necessary, to hold any Shares that are tendered into the Offer such that the Offeror and its affiliates will not hold more than 24.9% of the Shares (including any Shares currently held by the Offeror’s affiliates). If more than 20% of the Shares are tendered into the Offer, then (i) the Offeror would hold up to 24.9% of the Shares (including the 4.9% of the Shares that are currently held by the Offeror’s affiliates) and (ii) contribute any Shares in excess of 24.9% of the Shares into one or more Trusts to be held pursuant to the Trust Agreements.

WHO WILL BE THE BENEFICIARY OF THE TRUSTS?

The Offeror and its affiliates will not own, vote or control more than 24.9% of the Shares. In event that that more than 20% of Shares are tendered into the Offer such that the Offeror and its affiliates would own more than 24.9% of the Shares upon the closing of the Offer, all Shares in excess of 24.9% will be placed in one or more Trusts. The Shares held in such Trusts will ultimately be held for the benefit of the Offeror. Other than customary fees paid for serving in its capacity as trustee, the trustees will not derive any benefit from the ownership of the Shares held in such Trusts. While the Offeror will be a beneficiary of such Trusts, the record ownership of the Shares will be held by the Trusts and voting of the Shares in such Trusts will be in accordance with the Trust Agreements.

HOW LONG WILL THE TRUSTS HOLD THE SHARES?

The Trusts are intended to hold any Shares in excess of 24.9% from the closing of the Offer until such time as the earlier of (i) any required regulatory approval is denied or any applicable regulatory authority has indicated that such approval will be denied; (ii) any required regulatory approval is subject to the imposition of conditions that the Offeror (or its affiliate), by written notice to the trustees, has deemed to be unacceptable or any applicable regulatory authority has indicated that such approval will be subject to the imposition of conditions that the

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Offeror (or its affiliate), by written notice to the trustees, has deemed to be unacceptable, and (iii) two years from the date on which the Shares are placed in the Trusts. The process for obtaining any required regulatory approvals would occur after the closing of the Offer.

ARE ANY REGULATORY APPROVALS REQUIRED TO BE OBTAINED PRIOR TO THE CLOSING OF THE OFFER THAT HAVE NOT BEEN OBTAINED?

No. There are no outstanding required regulatory approvals that must be satisfied prior to the closing of the Offer. The waiting period under the HSR Act expired with respect to the Offer on November 1, 2021. In addition, the Trusts and the Trust Agreements, which will limit the number of Shares that the Offeror and its affiliates are entitled to vote to a maximum of 24.9% of the Shares, allow the Offeror to close the Offer and accept all Shares that are validly tendered and not withdrawn in the Offer, without first obtaining regulatory approvals that may have otherwise been required if the closing of the Offer would have resulted in the Offeror obtaining voting power or control in excess of 24.9% of the Shares.

WHAT ARE THE REGULATORY APPROVALS THAT THE OFFEROR REFERS TO IN THE OFFER?

When we refer to “regulatory approvals,” we are referring to the expiration or termination of any applicable waiting period (and extensions thereof) under the HSR Act and any necessary approvals from the appropriate regulatory authorities located in each of Arizona, California and Nevada. The waiting period under the HSR Act expired with respect to the Offer on November 1, 2021. As a result of the Trusts and the Trust Agreements, the Offeror (and its affiliates) will not control more than 24.9% of the voting power of the Company no matter how many Shares are tendered into the Offer such that regulatory approval thresholds in Arizona, California and Nevada will not be triggered at the closing of the Offer. Accordingly, there are currently no outstanding required regulatory approvals that must be satisfied prior to the closing of the Offer.

WILL ANY REGULATORY APPROVALS BE REQUIRED TO BE OBTAINED FOLLOWING THE CLOSING OF THE OFFER?

Any future need to obtain regulatory approvals in Arizona, California and Nevada would be unrelated to the closing of the Offer and will ultimately depend on whether a change of control may occur. The factors vary from state to state but will depend on (i) the number of Shares that are tendered into the Offer and (ii) whether the Offeror (or its affiliates) wish to exercise any voting rights, direction or control over the Shares that are held in Trust.

ARE THERE ANY REGULATORY APPROVALS REQUIRED TO SEAT THE ICAHN NOMINEES IF SUCH NOMINEES ARE ELECTED?

No. The Offeror is not aware of any regulatory approvals that would be required to seat the Icahn Nominees or for the Icahn Nominees to constitute a majority of the Board. However, there is no specific precedent that addresses this particular issue in Arizona, California or Nevada. It is possible that a preliminary or permanent injunction or other order of any federal or state court, government or governmental authority or agency could be issued and shall remain in effect at the time of the Annual Meeting, which would prevent the Icahn Nominees if elected from being seated at the Annual Meeting. In order to address this limited situation, the Participants in the proxy solicitation have included the Special Meeting Proposal, which asks that the stockholders approve the proposal to call a special meeting of the Company’s stockholders where the Board shall permit the nomination of the Icahn Nominees no later than 45 days following the receipt of all required governmental or regulatory approvals, consents, clearances or waivers which, in each case, have not been appealed and are no longer appealable, only if it is determined that such regulatory approvals are required to be obtained despite structuring the closing of the Icahn tender offer to avoid the need for any such approvals, in order for the Icahn Nominees to serve on the Board.

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IF THE OFFER IS COMPLETED, WILL SOUTHWEST GAS CONTINUE AS A PUBLICLY LISTED COMPANY?

If the conditions of the Offer as set forth in Section 14 of the Offer to Purchase — “CONDITIONS OF THE OFFER” are satisfied or waived and we complete the Offer, the number of stockholders and the number of Shares that are held by the public will be reduced and such number of stockholders and such number of Shares, depending on the number of Shares tendered in the Offer, may be so small that there may no longer be an active public trading market (or, possibly, there may not be any public trading market) for the Shares. Also, it is possible that Southwest may no longer be required to make filings with the SEC or otherwise comply with the rules of the SEC relating to publicly held companies on account of its equity interests. See Section 11 of the Offer to Purchase — “PURPOSE OF THE OFFER; PLANS FOR THE COMPANY” and Section 12 of the Offer to Purchase — “CERTAIN EFFECTS OF THE OFFER”.

ARE APPRAISAL RIGHTS AVAILABLE IN THE OFFER?

Appraisal rights are not available in the Offer. See Section 15 of the Offer to Purchase — “CERTAIN LEGAL MATTERS; REGULATORY APPROVALS; APPRAISAL RIGHTS”.

HOW DO I TENDER MY SHARES?

To tender your Shares, you must deliver the certificates representing your shares of Common Stock and, if certificates have been issued in respect of Rights prior to the Expiration Date, certificates representing the associated Rights, together with a completed Letter of Transmittal, to Continental Stock Transfer & Trust Company, the Depositary for the Offer, before the time the Offer expires. If your Shares are held in “street name” through a bank, broker or other nominee, the Shares can be tendered by your bank, broker or other nominee through The Depository Trust Company (“DTC”). If you cannot get any document or instrument that is required to be delivered to the Depositary by the Expiration Date, you may get additional time to do so by having a broker, a bank or other fiduciary that is a member of the Securities Transfer Agents Medallion Program or other eligible institution guarantee that the missing items will be received by the Depositary within two NYSE trading days after the date of execution of the notice of guaranteed delivery. For the tender to be valid, however, the Depositary must receive the missing items within that two-trading day period.

IF I TENDERED MY SHARES BEFORE THE OFFER PRICE WAS INCREASED TO $82.50 PER SHARE, DO I HAVE TO DO ANYTHING NOW?

No. Stockholders do not have to take any action regarding any Shares previously tendered and not properly withdrawn pursuant to the Offer. Such Shares constitute valid tenders for purposes of the Offer. If the Offer is completed, these Shares will be accepted for payment by the Offeror pursuant to the terms of the Offer and such stockholders will receive the same increased Offer Price as all other tendering stockholders of Southwest Gas. See Section 2 — “PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES”.

Although the Letter of Transmittal and Notice of Guaranteed Delivery previously circulated refer only to the Offer to Purchase, dated October 27, 2021, stockholders using such Letters of Transmittal and Notice of Guaranteed Delivery to tender their Shares will nevertheless be deemed to be tendering pursuant to the Offer subject to the terms and conditions set forth in the Offer to Purchase, dated October 27, 2021, as supplemented by this Supplement to the Offer to Purchase, dated December 7, 2021. See Section 2 of the Offer to Purchase — “PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES”.

UNTIL WHAT TIME CAN I WITHDRAW PREVIOUSLY TENDERED SHARES?

Tenders of Shares made pursuant to the Offer may be withdrawn at any time prior to the Expiration Date. If all conditions of the Offer have been satisfied on the Expiration Date, the Offeror will deposit with the Depositary

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the proceeds required to complete the Offer and will promptly accept for payment and pay for all properly tendered Shares that have not been withdrawn. See Section 1 of the Offer to Purchase — “TERMS OF THE OFFER” and Section 3 — “WITHDRAWAL RIGHTS”.

HOW DO I WITHDRAW PREVIOUSLY TENDERED SHARES?

To withdraw Shares, you must deliver a written notice of withdrawal, or a facsimile of one, with the required information to the Depositary while you still have the right to withdraw the Shares. See Section 3 of the Offer to Purchase — “WITHDRAWAL RIGHTS”.

WHAT ARE THE UNITED STATES FEDERAL INCOME TAX CONSEQUENCES OF THE OFFER?

If you are a U.S. holder, the receipt of the Offer Price pursuant to the Offer will be a taxable transaction for U.S. federal income tax purposes and may also be a taxable transaction under applicable state, local, or foreign income or other tax laws. Stockholders are urged to consult with their own tax advisors to determine the particular tax consequences to them (including the application and effect of any state, local or foreign income and other tax laws) of the Offer. For a more detailed explanation of the U.S. federal income tax considerations relevant to the Offer, see Section 5 of the Offer to Purchase — “MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS”.

WHO CAN I TALK TO IF I HAVE QUESTIONS ABOUT THE TENDER OFFER?

You can call Harkins Kovler, LLC at the following numbers: Banks and Brokerage Firms Call Collect at +1 (212) 468-5380 and all others call Toll Free at +1 (800) 326-5997. Harkins Kovler, LLC is acting as the Information Agent for the Offer.

WHERE TO FIND MORE INFORMATION REGARDING THE OFFER

IEP Utility Holdings filed a Tender Offer Statement and related exhibits with the SEC on October 27, 2021. The Company filed a Solicitation/Recommendation Statement with respect to the tender offer with the SEC on November 9, 2021. Stockholders of the Company are strongly advised to read the Tender Offer Statement (including the related exhibits) and the Solicitation/Recommendation Statement, as they may be amended from time to time, because they contain important information that stockholders should consider before making any decision regarding tendering their Shares. The Tender Offer Statement (including the related exhibits) and the Solicitation/recommendation Statement are available at no charge on the SEC’s website at www.sec.gov. The Tender Offer Statement and other documents that are filed by IEP Utility Holdings LLC with the SEC will be made available to all stockholders of the Company free of charge upon request to the information agent for the tender offer. The information agent for the tender offer is Harkins Kovler, LLC, 3 Columbus Circle, 15^th Floor, New York, NY 10019, toll-free telephone: +1 (800) 326-5997, email: swx@harkinskovler.com.

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ANNEX I: INFORMATION REGARDING THE PARTICIPANTS

This proxy solicitation is being made by the Participants. The Participants filing this statement include Icahn Partners LP (“Icahn Partners”), Icahn Onshore LP (“Icahn Onshore”), Icahn Partners Master Fund LP (“Icahn Master”), Icahn Offshore LP (“Icahn Offshore”), Icahn Capital LP (“Icahn Capital”), IPH GP LLC (“IPH”), Icahn Enterprises Holdings L.P. (“Icahn Enterprises Holdings”), Icahn Enterprises G.P. Inc. (“Icahn Enterprises GP”), Beckton Corp. (“Beckton”), Carl C. Icahn, a citizen of the United States of America, and each of the following individuals: Ms. Nora Mead Brownell, Ms. Marcie L. Edwards, Mr. Andrew W. Evans, Mr. H. Russell Frisby, Jr., Mr. Walter M. Higgins III, Ms. Rina Joshi, Mr. Henry P. Linginfelter, Mr. Jesse A. Lynn, Ms. Ruby Sharma, Mr. Andrew J. Teno, and Mr. David Adame, each of whom is a citizen of the United States of America. Ms. Nora Mead Brownell, Ms. Marcie L. Edwards, Mr. Andrew W. Evans, Mr. H. Russell Frisby, Jr., Mr. Walter M. Higgins III, Ms. Rina Joshi, Mr. Henry P. Linginfelter, Mr. Jesse A. Lynn, Ms. Ruby Sharma, and Mr. Andrew J. Teno are collectively referred to as the “Icahn Nominees”.

Icahn Partners, Icahn Onshore, Icahn Master, Icahn Offshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton, and Mr. Icahn are collectively referred to as the “Icahn Participants.”

The principal business address of Mr. Icahn, Icahn Partners, Icahn Onshore, Icahn Master, Icahn Offshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton, Mr. Lynn and Mr. Teno is c/o Icahn Enterprises L.P., 16690 Collins Ave., PH-1, Sunny Isles Beach, FL 33160. The principal business address of each of the Icahn Nominees is set forth in the Proxy Statement.

Icahn Onshore is the general partner of Icahn Partners. Icahn Offshore is the general partner of Icahn Master. Icahn Capital is the general partner of each of Icahn Onshore and Icahn Offshore. Icahn Enterprises Holdings is the sole member of IPH, which is the general partner of Icahn Capital. Beckton is the sole stockholder of Icahn Enterprises GP, which is the general partner of Icahn Enterprises Holdings. Carl C. Icahn is the sole stockholder of Beckton. As such, Mr. Icahn is in a position indirectly to determine the investment and voting decisions made by each of Icahn Partners, Icahn Onshore, Icahn Master, Icahn Offshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, and Beckton (such entities are referred to collectively with Mr. Icahn as the “Beneficial Owners”). In addition, Mr. Icahn is the indirect holder of approximately 90.2% of the outstanding depositary units representing limited partnership interests in Icahn Enterprises L.P. (“Icahn Enterprises”). Icahn Enterprises GP is the general partner of Icahn Enterprises, which is the sole limited partner of Icahn Enterprises Holdings.

Each of Icahn Partners and Icahn Master is primarily engaged in the business of investing in securities. Icahn Onshore is primarily engaged in the business of serving as the general partner of Icahn Partners. Icahn Offshore is primarily engaged in the business of serving as the general partner of Icahn Master. Icahn Capital is primarily engaged in the business of serving as the general partner of each of Icahn Onshore and Icahn Offshore. IPH is primarily engaged in the business of serving as the general partner of Icahn Capital. Icahn Enterprises Holdings is primarily engaged in the business of holding direct or indirect interests in various operating businesses. Icahn Enterprises GP is primarily engaged in the business of serving as the general partner of each of Icahn Enterprises and Icahn Enterprises Holdings. Beckton is primarily engaged in the business of holding the capital stock of Icahn Enterprises GP.

The Beneficial Owners beneficially own, in the aggregate, 2,898,676 Shares, which represent approximately 4.8% of the outstanding Shares (based on 60,523,873 Shares stated to be outstanding at March 21, 2022, by the Company in its definitive proxy statement filed with the SEC on March 24, 2022).

Icahn Partners and Icahn Master have entered into, and may from time to time enter into one or more, cash-settled equity swaps with broker-dealers and other financial institutions and counterparties with respect to 1,075,174 Shares and 764,826 Shares, respectively, with reference prices and maturity dates that vary depending upon the terms of each such cash-settled swap. After giving effect to such transactions, Icahn Partners and Icahn Master may be deemed to have either increased or decreased economic exposure to the securities of the

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Company. Icahn Partners and Icahn Master do not have voting power or dispositive power with respect to the Shares referenced in such cash settled swaps and disclaim beneficial ownership of the Shares to which such swaps relate.

Except to the extent of any pecuniary interest therein, the other Participants are not entitled to the right to the dividends on the Shares.

In addition to Icahn Partners, Icahn Onshore, Icahn Master, Icahn Offshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton, and Mr. Icahn, the participants in the solicitation of proxies (the “Participants”) from stockholders of Southwest Gas may also include Nora Mead Brownell, Marcie L. Edwards, Andrew W. Evans, H. Russell Frisby, Jr., Walter M. Higgins III, Rina Joshi, Henry P. Linginfelter, Jesse A. Lynn, Ruby Sharma, Andrew J. Teno, and David Adame. Ms. Brownell, Ms. Edwards, Mr. Evans, Mr. Frisby, Mr. Higgins, Ms. Joshi, Mr. Linginfelter, Mr. Lynn, Ms. Sharma, Mr. Teno and Mr. Adame will not receive any special compensation in connection with this solicitation.

In addition, the Participants may also include Brett Icahn, Andrew Teno and Jesse A. Lynn, each of whom is employed, and therefore compensated, by Icahn Enterprises or its affiliates. These individuals do not beneficially own any Shares. From time to time, these individuals have served on boards of directors of entities in which Icahn Enterprises or its affiliates have an interest. In such situations where Icahn Enterprises does not control such entities, these individuals receive customary director compensation from such entities (which may include cash fees, equity awards, reimbursement of travel expenses, indemnification and the like). Pursuant to the limited partnership agreement of Icahn Enterprises (filed as Exhibit 3.1 to Icahn Enterprises’ Form 10-Q for the quarterly period ended June 30, 2016, filed with the SEC on August 4, 2016), these individuals are entitled to indemnification for certain losses and expenses incurred in connection with proxy contests and service as directors on boards of directors of companies in which Icahn Enterprises or its affiliates have an interest (including the proxy contest relating to the Annual Meeting of the Company’s stockholders and any service as a director on the Company’s board of directors). Each of Messrs. Icahn, Teno and Lynn are party to employment agreements with Icahn Enterprises or its affiliates. Pursuant to the employment agreements with Messrs. Icahn and Teno, under certain circumstances, they will be eligible to receive certain profit sharing payments relating to net investment gains over a specified hurdle for certain investments held by affiliates of Icahn Capital (which such investments include the Shares). These individuals will not otherwise receive any special compensation in connection with the solicitation of proxies from stockholders of the Company.

Icahn Partners and the Beneficial Owners have indicated that if the Icahn Nominees are elected, then the Icahn Nominees plan to seek to add a director from Arizona to the Company’s Board of Directors. Icahn Partners and the Beneficial Owners believe that David Adame is a strong candidate for this position. As Mr. Adame is not an Icahn Nominee and does not own any Shares, Icahn Partners and the Beneficial Owners do not believe Mr. Adame qualifies as a Participant. Notwithstanding the foregoing, Mr. Adame has been included herein solely to the extent that he may be deemed to be a Participant. Mr. Adame currently serves, and has since 2015, as the President and Chief Executive Officer of Chicanos Por La Causa, one of the nation’s largest community development corporations. Mr. Adame’s principal business address is 1112 E. Buckeye Road, Phoenix, Arizona 85034. Mr. Adame will not receive any special compensation in connection with the solicitation of proxies from stockholders of the Company. Mr. Adame does not have any relationship with the Company or any of its affiliates. In addition, Mr. Adame does not have any agreements, understandings or relationships with Icahn Partners or any of the Beneficial Owners.

Icahn Partners has sole voting power and sole dispositive power with regard to 1,694,184 Shares. Each of Icahn Onshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton and Mr. Icahn has shared voting power and shared dispositive power with regard to such Shares. Icahn Master has sole voting power and sole dispositive power with regard to 1,204,492 Shares. Each of Icahn Offshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton and Mr. Icahn has shared voting power and shared dispositive power with regard to such Shares.

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Each of Icahn Onshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton and Mr. Icahn, by virtue of their relationships to Icahn Partners, may be deemed to indirectly beneficially own (as that term is defined in Rule 13d-3 under the Exchange Act) the Shares which Icahn Partners directly beneficially owns. Each of Icahn Onshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton and Mr. Icahn disclaims beneficial ownership of such Shares for all other purposes. Each of Icahn Offshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton and Mr. Icahn, by virtue of their relationships to Icahn Master, may be deemed to indirectly beneficially own (as that term is defined in Rule 13d-3 under the Exchange Act) the Shares which Icahn Master directly beneficially owns. Each of Icahn Offshore, Icahn Capital, IPH, Icahn Enterprises Holdings, Icahn Enterprises GP, Beckton and Mr. Icahn disclaims beneficial ownership of such Shares for all other purposes.

None of the Icahn Nominees nor Mr. Adame own any Shares of Southwest Gas beneficially or of record. None of the Icahn Nominees nor Mr. Adame has effected any transactions in the securities of Southwest Gas during the past two years.

Except as set forth in this Proxy Statement (including the Annexes), (i) during the past ten years, no Participant has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors); (ii) no Participant directly or indirectly beneficially owns any securities of the Company; (iii) no Participant owns any securities of the Company which are owned of record but not beneficially; (iv) no Participant has purchased or sold any securities of the Company during the past two years; (v) no part of the purchase price or market value of the securities of the Company owned by any Participant is represented by funds borrowed or otherwise obtained for the purpose of acquiring or holding such securities; (vi) no Participant is, or within the past year was, a party to any contract, arrangement, or understanding with any person with respect to any securities of the Company, including, but not limited to, joint ventures, loan or option arrangements, puts or calls, guarantees against loss or guarantees of profit, division of losses or profits, or the giving or withholding of proxies; (vii) no associate of any Participant owns beneficially, directly or indirectly, any securities of the Company; (viii) no Participant owns beneficially, directly or indirectly, any securities of any parent or subsidiary of the Company; (ix) no Participant nor any of their respective associates was a party to any transaction, or series of similar transactions, since the beginning of the Company’s last fiscal year, or is a party to any currently proposed transaction, or series of similar transactions, to which the Company or any of its subsidiaries was or is to be a party, in which the amount involved exceeds $120,000; (x) no Participant nor any of their respective associates has any arrangement or understanding with any person with respect to any future employment by the Company or its affiliates, or with respect to any future transactions to which the Company or any of its affiliates will or may be a party; and (xi) no person, including the Participants, has a substantial interest, direct or indirect, by security holdings or otherwise in any matter to be acted on as set forth in this Proxy Statement. There are no material proceedings to which the Participants or any of their respective associates is a party adverse to the Company or any of its subsidiaries or has a material interest adverse to the Company or any of its subsidiaries.

During the last fiscal year, neither any Icahn Nominee nor any Icahn Participant has failed to file reports related to the Company that are required by Section 16(a) of the Exchange Act.

To the best knowledge of the Participants, the Participants believe that each of the Icahn Nominees is independent under the applicable rules of NYSE and Southwest Gas’ corporate governance guidelines.

Except as set forth in this Proxy Statement (including the Annexes), the Icahn Participants are not the members of a “group” (as such term is used in Rule 13d-5 of the Exchange Act) or otherwise acting in concert with any other person.

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