Proxy Statement (Form DEF 14A)

This summary highlights selected information about the items to be voted on at the 2026 annual meeting of stockholders (the "Annual Meeting") of Quanta Services, Inc. (together with its subsidiaries, "Quanta" or the "Company"). This summary does not contain all of the information that you should consider in deciding how to vote. You should read the entire Proxy Statement carefully before voting.

Annual Meeting Agenda and

Voting Recommendations

Stockholders are being asked to vote on three agenda matters:

Voting Your Shares

Your vote is important. Even if you plan to attend the Annual Meeting in person, the Board of Directors of Quanta (the "Board") recommends that you cast your vote as soon as possible. Stockholders of record may vote by any of the below methods.

PROXY STATEMENT SUMMARY

Proposal 1: Election of Directors

Director Nominees

The table below provides summary information about each director nominee. Each director nominee is elected annually by a majority of votes cast.

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PROXY STATEMENT SUMMARY

Snapshot of 2026 Director Nominees

Board Qualifications, Skills and Experience

The Board regularly reviews the desired qualifications, skills and experiences that it believes are appropriate to oversee Quanta's business and long-term strategy. Attributes brought by director nominees include:

Corporate Governance Highlights

We are committed to strong governance standards, as evidenced by the key best practices below.

✓Annual election of directors

✓Majority voting standard for election of directors in uncontested elections

✓Director resignation policy

✓Holders of Quanta common stock vote as a single class on all matters

✓Separate Independent Chairman of the Board and Chief Executive Officer

✓Annual stockholder engagement

✓Robust stock ownership requirements for directors and officers

PROXY STATEMENT SUMMARY

✓Meaningful annual limit on non-employeedirector compensation

✓Code of Conduct that applies to all directors, officers and employees

✓Robust oversight process of business strategy, risk management and corporate sustainability and responsibility matters

✓Commitment to Board refreshment and composition aligned with the strategic direction of the Company

Proposal 2: Advisory Vote to Approve Named Executive Officer Compensation

Compensation Overview

During 2025, Quanta continued to utilize its innovative approach to its infrastructure solutions, combined with the strength of its portfolio of services, to perform at a high level and produce superior operational and financial results. Quanta achieved many strategic, operational and financial accomplishments throughout the Company. The Company achieved many record financial results, including record annual revenues, net income attributable to common stock, adjusted EBITDA and earnings per share, as well as record net cash provided by operating activities and free cash flow. Quanta also ended 2025 with record remaining performance obligations and backlog, exemplifying the accelerating demand across the Company's markets and positioning the Company well for 2026.

Quanta continued to develop and expand key service offerings and enhance the Company's position as a total solutions provider for its customers as they continue to execute significant capital budgets in response to overall load growth, which is being driven by technology advancements and grid resilience and security initiatives. In furtherance of these strategic initiatives, during 2025 Quanta completed eight acquisitions that augmented its existing solutions offerings, including with respect to mechanical infrastructure solutions, civil solutions and aviation services, as well as a strategic supply chain investment in a company that specializes in harvesting, treating and manufacturing wood poles for the utility and telecommunication industries. Of note, Quanta completed the strategic acquisition of Dynamic Systems (DSI), LLC, a provider of turnkey mechanical, plumbing and process infrastructure solutions to a diversified customer base that includes technology, semiconductor, healthcare and other load center markets, which provides Quanta with a mechanical solutions platform that expands and diversifies its customer base and enhances its ability to provide cost- and labor-certain infrastructure solutions at scale. Quanta believes its consistent performance and these accomplishments are indicative of the strength of its solutions-based strategy and remains focused on delivering superior financial performance and returning value to its stockholders. Quanta also remains focused on continuing its commitments to all stakeholders of the Company, including the safety and training of its workforce and responsible performance within communities in which it operates.

With respect to performance under the Company's 2025 annual incentive plan, the overall achievement percentage was 126.8% of target performance, which was driven by significant year-over-year improvement and above-target performance with respect to the earnings- and margin-based performance metrics, partially offset by performance slightly below target with respect to the safety performance improvement metric. Quanta also completed an exceptional 2023-2025 performance cycle that resulted in an achievement percentage of 188.5% of target performance under the 2023 long-term incentive plan, driven by continued improvement in the utilization of capital. Additionally, the financial performance targets and metrics included in the Company's 2025 annual and long-term incentive plans continue to generally represent improvement over historical performance and prior targets and support Quanta's strategic initiatives with respect to increased earnings and improvement in return on invested capital.

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PROXY STATEMENT SUMMARY

2025 Target Compensation Mix

Quanta's named executive officer ("NEO") compensation is primarily comprised of base salary, short-term cash incentives and long-term equity incentives. Target award levels generally reflect competitive market levels and practices, with upside opportunity for performance above target levels, and performance measures are chosen to align the interests of executives with stockholders.

2025 Long-Term Incentive Plan Equity Mix

A significant portion of equity-based incentive awards (70% with respect to the Chief Executive Officer ("CEO") and President of Electric Power and 60% with respect to other NEOs) is tied to measurable Company performance over a 3-yearperformance period.

PROXY STATEMENT SUMMARY

Elements of Executive Compensation

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PROXY STATEMENT SUMMARY

Compensation Governance

We are committed to strong governance standards that ensure our executive compensation program is closely aligned with the interests of our stockholders and other stakeholders, as evidenced by the policies and practices described below.

Proposal 3: Ratification of the Appointment of Independent Registered Public Accounting Firm

TABLE OF

CONTENTS

Board Recommendation ✓ X

QUANTA BOARD OF DIRECTORS

Proposal 1: Election of Directors

The Board currently consists of ten directors, whose current terms of office all expire at the Annual Meeting. Raúl Valentín, currently a member of our Board, has chosen not to stand, and has not been nominated for, re-electionat the Annual Meeting. Having considered the size, structure and composition of the Board, as well as the strategic direction of the Company and the Board's responsibility for oversight of risks facing the Company, and based on the recommendation of the Governance and Nominating Committee, the Board approved the nomination of Joseph Kim for election at the Annual Meeting, so that the Board shall thereafter continue to consist of ten directors until otherwise determined in accordance with Quanta's bylaws.

The Board proposes that the following ten nominees be elected for a new term of one year or until their successors are duly elected and qualified or until their earlier death, resignation or removal. Each of the nominees has consented to serve if elected. If a nominee becomes unwilling or unavailable to serve as a director, the Board may designate a substitute nominee or reduce the number of directors that constitute the Board. In that case, the persons named as proxies will vote for the substitute nominee designated by the Board. Proxies cannot be voted for a greater number of persons than the number of nominees named below.

The Board unanimously recommends a vote FORthe election of Ms. Ladhani, Ms. dePass Olsovsky and Ms. Wyrsch and Messrs. Austin, Baxter, Beneby, Fried, Jackman, Kim and Rowe.

Director Nominees

The following provides biographical information about each director nominee, including a description of the experience, qualifications and skills that have led the Board to determine that each nominee should serve on the Board.

EARL C. (DUKE) AUSTIN, JR.

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Mix of Skills, Experience, and Other Attributes of Director Nominees

Our director nominees have an effective mix of backgrounds, knowledge, and skills. The table below provides a summary of certain collective competencies and attributes of the director nominees. The lack of an indicator for a particular item does not mean that the director nominee does not possess that skill or experience, and we look to each director to be knowledgeable in all of these areas. Rather, the indicator represents that the item is a core competency that the director nominee brings to the Board. Our director nominees also have a wide range of additional skills and experience not mentioned, which are further described in their biographies above.

QUANTA BOARD OF DIRECTORS

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CORPORATE

GOVERNANCE

We are committed to having sound corporate governance practices that maximize stockholder value in a manner consistent with legal requirements and the highest standards of integrity. In that regard, the Board has adopted guidelines that provide a framework for the governance of Quanta, and we continually review these guidelines and regularly monitor developments in the area of corporate governance. Our Corporate Governance Guidelines are posted in the Investors / Governance section of our website at www.quantaservices.com.

Board Leadership Structure

The Board believes that the leadership structure of Quanta's Board should include either an independent non-executiveChairman of the Board or a Lead Director who satisfies Quanta's standards for independence. In May 2024, the Board appointed Doyle Beneby, an independent director, as non-executiveChairman of the Board to serve as such until his successor is duly elected and qualified at the next annual meeting of the Board or until his earlier resignation or removal. The roles of Chairman of the Board and Chief Executive Officer were separated at Quanta in 2013, and the Board continues to believe that having a non-executiveChairman of the Board is in the best interests of the Company and its stockholders, due in part to the ever-increasing demands made on boards of directors under federal securities laws, national stock exchange rules and other federal and state regulations. The separation of the positions allows the Chairman of the Board to focus on management of Board matters, as described further below, and allows Quanta's Chief Executive Officer to focus his attention on managing our business. Additionally, we believe the separation of these roles contributes to the independence of the Board in its oversight role and in assessing the performance of our Chief Executive Officer and management generally.

The Board reviews its leadership structure from time to time to assess whether it continues to serve the best interests of Quanta and its stockholders. In the future, the Board may determine, based on changing circumstances or characteristics of the Board or the Company or otherwise, that a director who is not independent is best situated to serve as Executive Chairman of the Board. Factors that may impact that determination may include, but are not limited to, whether such Executive Chairman possesses the detailed and in-depthknowledge of the issues, opportunities and challenges facing Quanta and its business and is thus best positioned to develop agendas that ensure that the Board's time and attention are focused on the most critical matters. Such a determination could be impacted by, among other things, the future composition of the Board, including the length of tenure of the independent directors, or any succession plans for the Company's Chief Executive Officer. In the event such a determination is made, the Board believes there are effective counter-balancing measures to ensure that Quanta maintains high standards of corporate governance and proper independent oversight, including the requirement under our Corporate Governance Guidelines to appoint a Lead Director, as described further below.

If, in the future, the Board elects to have a unified leadership structure and appoints an Executive Chairman of the Board, we would publicly disclose such a change in a timely manner through a press release and/or a Current Report on Form 8-K.Pursuant to our Corporate Governance Guidelines, such determination would ultimately be made by the Board, and we generally would not expect to seek prior input from our stockholders regarding any specific decision-making process with respect to Board leadership. However, we have engaged in discussions with stockholders regarding board leadership structure in the past, including in connection with our annual stockholder engagement program described in Engagement and Communications with the Boardbelow. We value those discussions, as well as any additional feedback we receive on this issue in the future, and would expect to consider stockholder perspectives in connection with any future decisions on board leadership structure, including a decision to appoint an Executive Chairman of the Board instead of an independent non-executiveChairman of the Board.

CORPORATE GOVERNANCE

Chairman of the Board

Quanta's Corporate Governance Guidelines provide that the Board will appoint a Chairman of the Board, who may but need not be an employee of Quanta. The Chairman of the Board generally presides over all regular sessions of the Board and Quanta's annual meetings of stockholders. With input from the Chief Executive Officer (if the Chairman is an independent director), or in consultation with the Lead Director (if the Chairman is not an independent director), the Chairman sets the agenda for Board meetings, subject to the right of each Board member to suggest the inclusion of items on any agenda. The Chairman of the Board may vote at any meeting of the Board on any matter called to a vote, subject to the legal, fiduciary and governance requirements applicable to all members of the Board. The Chairman of the Board is not a member of the standing committees of the Board, but attends and participates in meetings of the Board committees, and provides input on the overall design and operation of the Board, including in connection with the evaluation process described in Board and Committee Evaluationsbelow.

If the Chairman of the Board is an independent director, the duties and responsibilities of the Chairman of the Board generally include the following:

The Chairman of the Board also participates and represents the Board in certain communications and engagements with stockholders and other stakeholders, including in connection with the Company's annual engagement process described in Engagement and Communications with the Boardbelow. Additional duties and responsibilities of the Chairman of the Board may be established from time to time by the Board and the Governance and Nominating Committee of the Board.

Lead Director

In the event the Chairman of the Board is not an independent director, our Corporate Governance Guidelines provide that a Lead Director will be elected exclusively by the independent directors. The Lead Director must be an independent director and will assist the Chairman of the Board and the remainder of the Board in assuring effective corporate governance in managing the affairs of the Board. The Lead Director is responsible for ensuring that the quality, quantity and timeliness of the flow of information between management and the Board enables the Board to fulfill its functions and fiduciary duties in an efficient and effective manner. In addition, the Lead Director will coordinate the activities of the other independent directors, preside over the Board when the Chairman of the Board is not present, consult with the Chairman of the Board as to agenda items for Board and committee meetings, and perform such other duties and responsibilities as the Board deems appropriate.

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Board's Role in Strategy

The Board recognizes the importance of ensuring that the Company's overall business strategy is designed to create long-term, sustainable value for stockholders and benefit all of Quanta's stakeholders. While the formulation and implementation of Quanta's strategy is primarily the responsibility of management, the Board plays an active oversight role, carried out primarily through regular reviews and discussions with management, including both broad-based presentations and more in-depthanalyses and discussions of specific areas of focus and evolving business, industry, societal, operating and economic conditions. Directors have full and free access to Quanta's management and Company information, and, as necessary and appropriate, directors may consult with independent legal, financial, accounting and other advisors.

Periodically, the Board undertakes a robust qualitative and quantitative review of management's five-year strategic plan, which includes both financial and operational performance goals and the strategic initiatives designed to support those goals. In connection with management's current five-year strategic plan, the Board and management discuss, among other things, key strategic initiatives, including those set forth below.

The Board also annually reexamines the strategic plan, reviewing management's progress on its strategic initiatives and revised financial projections based on, among other things, prior period financial results and recent acquisition activity. The Board and management discuss and consider, among other strategic matters, market and industry trends and opportunities; customer dynamics; the Company's competitive positioning; regulatory, legislative, political and legal changes; and emerging technologies and challenges in the industries Quanta serves. Furthermore, on an ongoing basis, the Board and committees of the Board (as applicable) evaluate specific business decisions in light of the strategic plan, including proposed acquisitions or investments, capital allocation decisions, significant project opportunities, and key safety, training and technology initiatives. The Board's oversight of risk management (as described below) also enhances the directors' understanding of the risks associated with the Company's strategy and the Board's ability to provide guidance to and oversight of management in executing the strategic plan.

Board's Role in Risk Oversight

The Board oversees an enterprise-wide approach to risk management, designed to support the achievement of long-term organizational objectives and enhance stockholder value. The Company's enterprise risk management assessment, managed by Quanta's Chief Executive Officer, General Counsel and Chief Financial Officer, as well as Quanta's Chief Compliance Officer (who reports to the General Counsel), provides visibility to the Board about the identification, assessment, monitoring and management of critical risks and management's risk mitigation strategies. During this ongoing process, risks are assessed throughout the Company's business, including operational, industry, financial and reputational risks, legal and regulatory risks and data and systems security risks. A component of the Board's oversight function is not only understanding the risks the Company faces and what steps management is taking to manage those risks, but also understanding what level of risk is appropriate for Quanta. The involvement of the full Board in setting Quanta's business strategy, both short-term and long-term, is a key part of its understanding of Quanta's risks and how those risks may evolve in response to changes in strategy or business environment, and what constitutes an appropriate level of risk for Quanta.

CORPORATE GOVERNANCE

While formal reporting associated with the Company's enterprise-wide risk management assessment is produced for the Board and the Safety, Operations and Risk Committee on an annual cycle, the Board and committees of the Board continually evaluate and consider risks that are impacting, or could potentially impact, the Company throughout the entire year, including through dialogue with management at Board and committee meetings. Additional discussions and evaluations of risks can arise in connection with, among other things, development and/or review of the Company's business strategy, evaluation of the Company's performance or operations, evaluation of a potential strategic acquisition or project opportunity and overall trends that could accelerate or increase the impact of a potential risk. Further, the Board utilizes its committee structure to facilitate more detailed and nuanced consideration of certain risks on an ongoing basis (as set forth in further detail below) and in making determinations as to whether to retain direct oversight of a risk or assign oversight to a committee, the Board considers various factors, including, among other things, the importance of the risk to the Company's overall strategy and operations, the timeframe over which a risk may materialize (i.e., short-term, medium-term or long-term), the potential impact of a risk and how a risk aligns with the subject matter assigned to a committee. Additionally, to the extent the Board, a committee or management deems it necessary or appropriate, outside advisors and subject matter experts may be consulted when considering the development or potential impact of certain risks or in anticipation of future threats or trends with respect to certain risks.

Review and discussion of the results of the Company's annual risk management assessment with both the Safety, Operations and Risk Committee and the Board, as well as further dialogue between management and the Board and committees throughout the remainder of the year, helps inform and shape the Company's risk-related disclosures included in its periodic reports filed with the SEC and other public disclosures. For additional information regarding the risks facing the Company, review the risk factors included in Item 1A. of Part I of Quanta's Annual Report on Form 10-Kfor the fiscal year ended December 31, 2025. The risks described therein

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are not the only risks facing the Company, and additional risks and uncertainties not currently known, or that may currently be deemed to be immaterial based on the information known to the Company, may materially adversely affect the Company's business, financial condition or results of operations in future periods.

Board Independence

The Board has determined that each of our current directors and director nominees, other than our Chief Executive Officer, Mr. Austin, has no material relationship with Quanta (either directly or as a partner, stockholder or officer of an organization that has a relationship with Quanta) and is "independent" within the meaning of the NYSE corporate governance listing standards. The Board has made these determinations based in part on its finding that these independent directors meet the categorical standards for director independence set forth in our Corporate Governance Guidelines and in the NYSE corporate governance listing standards. When evaluating the independence of Mr. Baxter, the Board considered his service as a director of WEC Energy Group, a customer of Quanta. When evaluating the independence of Mr. Jackman, the Board considered Quanta's employment of his son, who is employed at a non-managementlevel, as described in Certain Transactions below. When evaluating the independence of Ms. Wyrsch, the Board considered her service as a director of National Grid plc, a customer of Quanta. The Board determined that these relationships were not material and that the positions held by these individuals and the amounts involved did not prevent a finding of independence under the NYSE standards or our Corporate Governance Guidelines. With each current director other than Mr. Austin deemed independent, the Board exceeds the NYSE requirement that a majority of directors be independent. The Board also evaluated the independence of Mr. Foster, a former director who served during a portion of fiscal year 2025, and determined that Mr. Foster was "independent" within the meaning of the NYSE corporate governance listing standards while he was a director.

Our Corporate Governance Guidelines, which include our categorical standards for director independence, are posted in the Investors / Governance section of our website at www.quantaservices.com.

Executive Sessions of Non-ManagementDirectors

In accordance with the NYSE corporate governance listing standards, our non-managementdirectors, each of whom is "independent" within the meaning of NYSE corporate governance listing standards and our Corporate Governance Guidelines, meet in executive session without management at each regularly scheduled Board meeting. The executive sessions are presided over by the Chairman of the Board or, if the Chairman of the Board is not independent, by the Lead Director, or in the absence of an independent Chairman of the Board or Lead Director, by an independent director selected by the executive session participants.

Director Meetings

During the year ended December 31, 2025, the Board held seven meetings. Each director attended greater than 75% of the meetings of the Board and the committees of the Board on which they served. We encourage, but do not require, the members of the Board to attend the annual meeting of stockholders. Last year, all directors attended the annual meeting of stockholders.

CORPORATE GOVERNANCE

Committees of the Board

The Board has five standing committees: the Audit Committee, the Compensation Committee, the Governance and Nominating Committee, the Finance and Investment Committee, and the Safety, Operations and Risk Committee. In 2025, the Board formed the Safety, Operations and Risk Committee and expanded the scope of the Finance and Investment Committee to allow more detailed review of certain matters previously reviewed by the entire Board, given their importance to the strategic direction and risk profile of the company.

The Board has examined the composition of each standing committee and has determined that each member of these committees is "independent" within the meaning of SEC regulations, NYSE corporate governance listing standards and our Corporate Governance Guidelines. Each standing committee operates under a formal charter adopted by the Board that governs its responsibilities, all of which are posted in the Investors / Governance section of our website at www.quantaservices.com. The current membership and the number of meetings held during the last fiscal year and the primary responsibilities of each committee are set forth below:

Audit Committee

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CORPORATE GOVERNANCE

Compensation Committee

CORPORATE GOVERNANCE

Governance and Nominating Committee

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Finance and Investment Committee

CORPORATE GOVERNANCE

Safety, Operations and Risk Committee

Compensation Committee Interlocks and Insider Participation

No member of the Compensation Committee served as an employee or officer of Quanta or any of its subsidiaries during 2025, was formerly an officer of Quanta or any of its subsidiaries, or had any relationship with Quanta requiring disclosure herein as a related party transaction. Additionally, no executive officers served on the compensation committee or as a director of another company, one of whose executive officers served on Quanta's Compensation Committee or as a director of Quanta.

Code of Conduct

The Board has adopted a Code of Conduct that applies to all directors, officers and employees of Quanta and its subsidiaries, including the principal executive officer, principal financial officer and principal accounting officer or controller. The Code of Conduct is posted in the Investors / Governance section of our website at www.quantaservices.com. We intend to post at the above location on our website any amendments or waivers to the Code of Conduct that are required to be disclosed pursuant to Item 5.05 of Form 8-K.

Engagement and Communications with the Board

The Board believes that effective corporate governance includes constructive conversations and the development of long-term relationships with our stockholders. We value such engagement and believe it is important to address any questions or concerns on Company policies and practices. We also review and analyze the voting results and feedback from our annual meetings to identify any topics of interest or concern.

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Members of our management have historically engaged in extensive investor outreach on a variety of financial and operational topics, including long-term strategy, capital allocation priorities and industry dynamics. In a given year, we have numerous interactions with stockholders and members of the investment community on these matters and host or participate in various investor conferences and events.

Quanta also conducts an annual stockholder engagement program focused on corporate responsibility and sustainability topics, as well as other governance- and compensation-related topics, including executive compensation, board structure and composition, oversight of strategy and risk, and equity incentive compensation grant practices. Our engagement team includes members of senior management, and when requested, independent directors or subject matter experts, and seeks to identify and address any areas of concern. During the fourth quarter of 2025 and first quarter of 2026, in connection with this program, we extended offers to engage with holders of a significant amount of Quanta's outstanding common stock as of December 31, 2025, including larger holders and specific institutional investors that expressed interest in engaging with the Company on these matters. Through discussions with these holders, management and the Board received and reviewed valuable feedback on several topics, including the topics set forth below.

Quanta values the feedback received from stockholders, as this feedback helps to inform subsequent discussions and decisions regarding our governance and compensation practices, as well as sustainability and corporate responsibility priorities.

CORPORATE GOVERNANCE

Stockholders and other interested parties may communicate with one or more of our directors, including our non-managementdirectors or independent directors as a group, a committee or the full Board by writing to Corporate Secretary at the address for our corporate headquarters, which is currently: Quanta Services, Inc., 2727 North Loop West, Houston, Texas 77008. All communications will be reviewed by the Corporate Secretary and forwarded to one or more of our directors, as appropriate.

Board and Committee Evaluations

Board and committee evaluations play an important role in ensuring the effective functioning of the Board. Therefore, the Board and each committee conduct annual self-assessments, which are overseen by the Governance and Nominating Committee. The results of these assessments are compiled, without attribution, and made available to the directors for a full Board assessment and to the committee members of each committee for a committee assessment. Additionally, the Chairman of the Board conducts one-on-onediscussions with each director to gather feedback on Board and committee operations, practices and performance. Information derived from the evaluation process is also considered by the Governance and Nominating Committee when searching for and evaluating potential future director candidates.

Identifying and Evaluating Nominees for Director

The Governance and Nominating Committee regularly evaluates the appropriate size of the Board and whether any vacancies on the Board are expected due to retirement or otherwise. If any vacancies are anticipated or arise, the Governance and Nominating Committee will consider director candidates suggested by incumbent directors, management, third-party search firms and others. The Governance and Nominating Committee will also consider director nominations by stockholders that are made in compliance with our bylaws. All applications, recommendations or proposed nominations for Board membership received by Quanta will be referred to the Governance and Nominating Committee. The manner in which the qualifications of a nominee are evaluated does not differ if the nominee is recommended by a stockholder.

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The Governance and Nominating Committee has the authority to retain, at Quanta's expense, a third-party search firm to help identify and facilitate the screening and interview process of potential director nominees. Once a potential director nominee is identified or recommended, the committee makes an initial determination as to whether to conduct a full evaluation based on, among other things, the information provided with the recommendation, the committee's own knowledge of the candidate, supplemental inquiries to the recommending person or others, or a background check. If the committee determines to further pursue the candidate, the candidate is evaluated based on the qualifications described below. After this evaluation, the committee determines whether to interview the candidate and may ask the candidate to meet with members of Quanta's management or other Board members. After completing its evaluation, if the committee believes the candidate would be a valuable addition to the Board, it will recommend to the Board the candidate's nomination for appointment or election as a director.

When evaluating director candidates, including new nominees and incumbent directors, the Governance and Nominating Committee considers all relevant factors it deems appropriate, such as, among other things, the current composition of the Board (including with respect to alignment of skills and experience with the Company's strategic plan and risks facing the Company), the balance of management and independent directors, the need for a certain Board committee expertise, and the candidate's activities unrelated to Quanta (including service as a director on the boards of other public companies). The Board also values diversity in its broadest sense and endeavors to have a group of directors representing broad-ranging experiences at policy-making levels of organizations that are relevant to Quanta's activities and operations, which may come from business, government, education, technology and non-profitorganizations; complementary tenure length, which ensures a proper balance between Board refreshment and director continuity; and varied backgrounds and attributes.

Director Qualifications

Our Corporate Governance Guidelines contain Board membership qualifications that the Governance and Nominating Committee considers in selecting nominees for the Board. The guidelines state that members of the Board should possess the highest standards of personal and professional ethics, integrity and values, and be committed to representing the long-term interests of our stockholders, and must have an inquisitive and objective perspective, practical wisdom, mature judgment, the willingness to speak their mind and the ability to challenge and stimulate management in a constructive manner. The guidelines also provide that Board members should have experience in areas that are relevant to Quanta's business and demonstrated leadership skills in the organizations with which they are or have been affiliated.

The Board also considers current director skills, experience and attributes when considering additional nominees for the Board, including additional or complementary skills, expertise or knowledge that may be necessary to support the current and anticipated needs of the Company and management.

Members of the Board must also be willing to devote sufficient time to carrying out their duties and responsibilities effectively and should be committed to serve for an extended period of time. As such, a Board member should not serve on more than four public company boards (including the Quanta Board), and a Board member that is a chief executive officer (or equivalent position) with another public company should not serve on more than three public company boards (including the Quanta Board). Additionally, members of the Quanta Audit Committee should not serve on more than three public company audit committees, including the Quanta Audit Committee. The Board determined that no director currently has time commitments that would prevent them from properly discharging their duties as directors. Board members will not be nominated for election to the Board if the election would occur after their 75th birthday; however, the full Board may make exceptions in special circumstances.

Director Compensation

The Governance and Nominating Committee has the responsibility of recommending to the Board compensation and benefits for non-employeedirectors. The committee is guided by certain director compensation principles set forth in our Corporate Governance Guidelines:

CORPORATE GOVERNANCE

The Governance and Nominating Committee and the Board aim to set director compensation levels at or near the market median relative to directors at companies of comparable size, industry, and scope of operations in order to ensure directors are paid competitively for their time commitment and responsibilities. A market competitive compensation package is important because it enables us to attract and retain highly qualified directors who are critical to our long-term success. Additional director compensation practices have been adopted to align with market best practices and ensure director interests are closely aligned with the interests of our stockholders as set forth below.

Director Compensation

Effective May 22, 2025, the Board increased the annual cash retainer for non-employeedirectors from $105,000 to $120,000 and the dollar value of the annual RSU award for non-employeedirectors from $165,000 to $180,000. Additionally, effective as of August 27, 2025, the Board created the Safety, Operations and Risk Committee and set the annual cash retainer for the committee chairmanship at $20,000 and the annual cash retainer for the committee members at $10,000. Following these changes, at every annual meeting of stockholders at which a non-employeedirector is elected or re-elected,each such director receives (i) an annual award of RSUs having a value of $180,000 and (ii) the applicable annual cash retainer(s) set forth in the table below.

Upon initial appointment to the Board other than at an annual meeting of stockholders, a non-employeedirector receives (for the period from the appointment through the end of the current director service year) a pro-rataportion of the annual equity award and applicable annual cash amounts. Our non-employeeChairman of the Board receives additional annual compensation in the amount of $200,000, of which 50% is payable in cash and 50% is payable in RSUs. Upon the initial appointment of a non-employeeChairman of the Board, other than immediately following the annual meeting of stockholders, such director receives (for the period from the appointment through the end of the current director service year) a pro rata portion of the additional annual compensation.

Unless the non-employeedirector's Board service is terminated earlier, RSUs generally vest in full upon conclusion of the director service year. Subject to the terms of applicable award agreements, unvested RSUs held by (i) any non-employeedirector who is not nominated for or elected to a new term, including for example, due to a reduction in the size of the Board, age precluding a re-nomination,the identification of a new nominee, or the desire to retire at the end of a term, or (ii) any non-employeedirector who resigns at Quanta's convenience, including any resignation resulting from the non-employeedirector's failure to receive a majority of

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CORPORATE GOVERNANCE

the votes cast in an election for directors as required by Quanta's bylaws, vest in full on the earlier of (a) the conclusion of the director service year, or (b) the date of such non-employeedirector's termination of service. RSUs are generally settled in shares of Quanta common stock, provided that a non-employeedirector may elect to settle up to 50% of any award in cash if he or she is in compliance with Quanta's stock ownership guidelines as of the date of settlement and is expected to remain in compliance immediately following settlement.

Generally, meeting fees are not paid to our non-employeedirectors. However, in order to compensate for the time required to accommodate extraordinary meeting activity, each non-employeedirector receives a fee for attendance at the tenth and any subsequent Board meeting or the tenth and any subsequent committee meeting, in each case during a single director service year, as follows: $2,000 for attendance at an in-personboard meeting; $1,000 for participation at a telephonic board meeting; $1,000 for attendance at an in-personcommittee meeting; and $500 for participation at a telephonic committee meeting.

Directors are also reimbursed for reasonable out-of-pocketexpenses incurred to attend meetings of the Board or the committees thereof, and for other expenses reasonably incurred in their capacity as directors of Quanta. Directors who are also employees of Quanta or any of its subsidiaries do not receive additional compensation for serving as directors. Currently, nine non-employeedirector nominees are standing for election at the annual meeting. As an executive officer of Quanta, Mr. Austin received no compensation for his service as a director of Quanta.

Annual Limit on Non-EmployeeDirector Compensation

The Quanta Services, Inc. 2019 Omnibus Equity Incentive Plan (as amended, the "2019 Omnibus Plan") contains an annual limit on non-employeedirector compensation, inclusive of all cash compensation and any awards under the 2019 Omnibus Plan that may be made to a non-employeedirector for service during any calendar year. The annual limit is $500,000 per year, provided that a newly elected director may receive up to $750,000 for his or her initial calendar year of service on the Board and a director serving as Chairman of the Board or Lead Director may receive up to $750,000 for service during any calendar year.

Deferred Compensation Plan for Non-EmployeeDirectors

Non-employeedirectors are eligible to participate in a deferred compensation plan maintained by Quanta. No later than December 31 of each year, each non-employeedirector may voluntarily elect to defer all or a portion (in 5% increments) of his or her annual cash retainers, including but not limited to, compensation for board membership, committee membership and board/committee leadership, and RSUs to be earned with respect to services performed in the following year. Deferral elections are irrevocable and if no deferral election is made, no compensation is deferred. Deferred cash amounts are allocated to a separate recordkeeping account maintained for the non-employeedirector that reflects the amounts deferred and any earnings (positive or negative). The account is credited with returns according to the performance of certain deemed investment choices selected by the non-employeedirector from time to time. However, Quanta has no obligation to provide any deemed investment choice other than a default investment option selected by the Compensation Committee. The interest rate earned on the deferred cash amounts is not above-market or preferential. Deferred RSUs are recorded in an account maintained for the non-employeedirector that reflects the number of shares deferred. Quanta also makes a cash payment of dividend equivalents on the shares deferred at the same time and at the same rate as dividends are paid on Quanta common stock. In general, deferred compensation is distributed to the non-employeedirector (or his or her beneficiary) upon the director leaving the Board or at a date elected in advance by the director. Additionally, deferred amounts can be distributed upon certain unforeseen emergencies suffered by the non-employeedirector or upon a change in control of Quanta.

Stock Ownership Guidelines for Non-EmployeeDirectors

Non-employeedirectors are required to hold stock with a value equivalent to five times the annual cash retainer for Board membership (excluding the annual cash retainer for committee membership or any supplement for serving as a committee chairman or as Chairman of the Board). Non-employeedirectors have five years from the fiscal year-endfollowing initial election to the Board to accumulate the stock ownership prescribed by the guidelines. As of December 31, 2025, all non-employeedirectors were in compliance with the requirements of the stock ownership guidelines. Specifically, Messrs. Beneby, Fried, Jackman, Rowe and Valentín and Ms. Wyrsch and Ms. Ladhani exceeded the prescribed ownership level, and Mr. Baxter and Ms. Olsovsky (each elected in May 2024), were making ratable progress toward the prescribed ownership level within their accumulation periods.

CORPORATE GOVERNANCE

2025 Director Compensation Table

The following table sets forth the compensation for each non-employeedirector during the 2025 fiscal year.

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EXECUTIVE

OFFICERS

The current executive officers of Quanta are as follows:

Earl C. (Duke) Austin, Jr.For a description of the business background of Mr. Austin, see Quanta Board of Directors - Director Nominees above.

Jayshree S. Desai has served as our Chief Financial Officer since July 2022. She previously served as our Chief Corporate Development Officer from January 2020 to July 2022. She also previously served as President and a director of ConnectGen LLC, a renewable energy company focused on utility-scale renewable energy and storage development, from July 2018 through December 2019, where she had primary responsibility for organizational management, business strategy and capital allocation. Ms. Desai also previously served as Chief Operating Officer of Clean Line Energy Partners LLC, an electric transmission development company, from January 2010 through July 2018, where she had primary responsibility for, among other things, strategic planning, finance and capital management and human resources. She also previously served as Chief Financial Officer of Horizon Wind Energy (now EDP Renewables North America), a renewable energy company, from 2002 through 2010, where she had primary responsibility for finance, accounting, tax, treasury and information technology operations. In addition, Ms. Desai has served as a director of TPI Composites, Inc., a publicly traded independent manufacturer of wind turbine components, since October 2017. Ms. Desai holds a Bachelor of Business Administration degree and a Master of Business Administration.

Karl W. Studer has served as our President of Electric Power since 2022. He previously served as a Regional Vice President of Quanta from 2018 to 2022, with oversight of operations and significant projects related to Quanta's electric power solutions. Mr. Studer co-foundedProbst Electric Inc. and Summit Line Construction, Inc., electric specialty companies that were acquired by Quanta in 2013. Following such acquisitions, he held several senior leadership roles of these operating companies, including President and Chief Executive Officer, with responsibility for, among other things, operations and financial matters. Mr. Studer is a certified journeyman lineman and a graduate of Northwest Lineman College in Meridian, Idaho.

Gerald A. (BJ) Ducey, Jr.has served as our President of Strategic Operations since May 2023. Mr. Ducey previously served as our Senior Vice President - Operations from May 2017 to May 2023 and various other management roles within Quanta from January 2012 to May 2017. Prior to joining Quanta, he served as Vice President - Operations and Business Development at Dashiell Corporation, a Quanta operating company, from August 2006 to January 2012. Mr. Ducey holds a Bachelor of Science in Mechanical Engineering and a Master of Business Administration.

Donald C. Waynehas served as our Executive Vice President and General Counsel since May 2017. He previously served as Senior Vice President, General Counsel and Corporate Secretary of Archrock, Inc., a publicly traded provider of natural gas compression and related products and services, from November 2015 through May 2017, and in similar roles for its predecessor companies, Exterran Holdings, Inc. and Universal Compression Holdings, Inc., from August 2006 through November 2015. Mr. Wayne also served, from August 2006 through May 2017, as Senior Vice President and General Counsel of Archrock GP LLC and in similar roles for the other managing general partners of Archrock Partners, L.P. and its predecessor entities, each a publicly traded master limited partnership, and as a director of Archrock GP LLC from November 2015 through May 2017. Mr. Wayne also previously served as Vice President and General Counsel of U.S. Concrete, Inc., a publicly traded provider of ready-mixed concrete and related products and services, from 1999 to 2006. Prior to joining U.S. Concrete, Inc., he served as an attorney with the law firm of Akin, Gump, Strauss, Hauer & Feld, L.L.P. Mr. Wayne holds a Bachelor of Arts degree, a Master of Business Administration and a Juris Doctor degree.

EXECUTIVE OFFICERS

Paul M. Nobelhas served as our Senior Vice President and Chief Accounting Officer since May 2023. He previously served as our Vice President and Chief Accounting Officer from May 2021 to May 2023. He also previously served as interim Chief Financial Officer of Lilis Energy, Inc., an oil and gas exploration and development company operating in Texas and New Mexico, from February 2020 to July 2020, where he had primary responsibility for finance and treasury functions. He also previously served as Senior Vice President and Chief Accounting Officer of Kosmos Energy Ltd., a publicly traded international full-cycle offshore oil and gas exploration and production company, from July 2012 to November 2019, and as Senior Vice President and Chief Accounting Officer of World Kinect Corporation (then, World Fuel Services Corporation), a publicly traded global energy management company serving commercial and industrial customers, from July 2005 to July 2012. In these previous positions, Mr. Nobel had primary responsibility for the accounting and reporting functions, tax, financial planning and analysis and risk management. He also previously served as a senior manager for the public accounting firm of Deloitte & Touche LLP. Mr. Nobel holds a Bachelor of Science degree in Accounting and is a Certified Public Accountant.

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COMPENSATION DISCUSSION & ANALYSIS

Compensation Committee Report

We have reviewed and discussed the following Compensation Discussion and Analysis with management. Based on our review and discussions with management, we have recommended to Quanta's Board of Directors that the Compensation Discussion and Analysis be included in this Proxy Statement.

This report is furnished by the Compensation Committee of the Board of Directors.

Scott Rowe, Chairman

Bernard Fried

Jo-annM. dePass Olsovsky

Raúl J. Valentín

Martha B. Wyrsch

Executive Summary

This Compensation Discussion and Analysis describes Quanta's executive compensation program for 2025. We use this program to attract, motivate and retain the employees who lead our Company. In particular, this section explains the Compensation Committee's guiding principles for executive compensation and how the Compensation Committee made its compensation decisions for our NEOs for 2025.

Named Executive Officers

Our NEOs for 2025 include the following five executive officers:

COMPENSATION DISCUSSION & ANALYSIS

Key 2025 Performance Highlights

During 2025, Quanta continued to execute and perform at a high level and produced superior financial and operating results, which reflects the strength of the Company's business portfolio, execution discipline and customer-focused approach. Quanta's proven business strategy, which leverages a broad portfolio of services designed to produce resilient and sustainable results, also enable the Company to navigate various ongoing challenges, including macroeconomic uncertainty, supply chain and logistical challenges with respect to certain materials and equipment, inflationary pressure and volatility in the capital markets. The accelerating demand for power and infrastructure solutions is reshaping our industry, and Quanta is at the center of this transformation. Quanta has remained focused on the execution of key strategic initiatives designed to position the Company for long-term success and deliver value to stakeholders. These initiatives include, among others, continuing to collaborate with customers on their efforts designed to modernize infrastructure and meet the growing demand for power, focusing on delivery of high-quality project execution, and expanding and differentiating the Company's service offerings.

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COMPENSATION DISCUSSION & ANALYSIS

Overview of 2025 Executive Compensation Decisions

Key executive compensation decisions by our Compensation Committee affecting our NEOs' 2025 compensation included the following.

COMPENSATION DISCUSSION & ANALYSIS

Say-on-PayVote

At Quanta's 2025 annual meeting of stockholders, approximately 93% of our stockholders voting on the "say-on-pay"proposal approved the compensation of our NEOs as described in our proxy statement filed in 2025. Accordingly, the Compensation Committee did not implement any changes to our executive compensation program as a result of the advisory vote. However, in connection with its ongoing review process and to continue to align with stockholder expectations and the Company's long-term strategic initiatives, the Compensation Committee did adjust the performance metrics included in, and the overall structure of, the 2025 long-term incentive plan, as set forth in further detail in Elements of Executive Compensation.

Additionally, as a key objective of our stockholder engagement program, which is described further in Corporate Governance - Engagement and Communications with the Board,members of senior management and the Board solicit feedback from stockholders on our executive compensation program that is relayed directly to the full Board to be considered when evaluating opportunities to further enhance our executive compensation programs and practices in future years. The Compensation Committee also continues to monitor trends and developments to ensure that Quanta provides the appropriate executive compensation incentives to remain competitively positioned to attract and retain executive talent and to ensure that management's interests are aligned with those of our stockholders.

How Our Performance is Linked to Pay

Quanta's NEO compensation is primarily comprised of base salary, annual cash incentives and long-term equity incentives. Our compensation philosophy links executive compensation to both individual and Company performance. Base salaries are generally set based on consideration of, among other things, the median of our competitive market, the nature of the position and the NEO's contributions, experience, level of responsibility and length of service. Target annual incentives generally reflect competitive market levels and practices, with upside opportunity for performance above target levels. Performance measures are designed to align the interests of executives with those of stockholders, reward successful achievement of annual financial and operational goals while maintaining focus on long-term financial performance and sustainability, and incentivize successful capital allocation strategies, as discussed in further detail in Executive Compensation Decisions for 2025.

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COMPENSATION DISCUSSION & ANALYSIS

2025 TARGET COMPENSATION MIX

The Compensation Committee considers the median target total direct compensation for officers in our peer group when setting compensation levels for each NEO. Additionally, the Compensation Committee believes that a significant portion of each NEO's target compensation should be at risk or variable. The short-term cash incentive awards and long-term equity incentive awards to our NEOs are considered "at risk" compensation because they are either tied to the level of performance compared to our incentive targets or peer group performance or are subject to continued employment and stock price performance during a 3-yearvesting period. Further, equity-based incentive awards under our 2025 long-term incentive plan represented a substantial portion of each NEO's compensation as a percentage of target total direct compensation and a significant portion of such equity-based incentive awards (70% with respect to the CEO and President - Electric Power and 60% with respect to the other NEOs) are subject to measurable company performance over a 3-yearperformance period. Equity-based awards play an important role in our compensation program because they provide incentives for the creation of stockholder value and promote executive retention and an ownership culture.

Good Governance and Best Practices

We are committed to strong governance standards that ensure our executive compensation programs are closely aligned with the interests of our stockholders, as evidenced by the policies and practices described below.

COMPENSATION DISCUSSION & ANALYSIS

Compensation Philosophy

Each member of the Compensation Committee is independent within the meaning of SEC regulations, the NYSE corporate governance listing standards and our Corporate Governance Guidelines. The Compensation Committee administers the compensation programs for all of our NEOs, and its guiding principles for NEO compensation are set forth below.

During the first quarter of the fiscal year, the Compensation Committee determines the terms of our annual and long-term incentive plans for that year and establishes the performance metrics that will be used in evaluating the performance of the NEOs under the plans. In addition, the Compensation Committee establishes prospective base salary rates and target incentive percentages for each NEO for the current annual and long-term performance periods. Following the end of the fiscal year, the Compensation Committee meets to discuss our prior year's performance, evaluate the performance of our NEOs, and determine the amounts, if any, that will be awarded to each NEO under the incentive plans.

As set forth above, the Compensation Committee seeks to maintain the competitiveness of our executive compensation levels with those of our peers and competitors. The Compensation Committee considers various factors in determining overall compensation and each compensation component, including (i) the results of compensation benchmarking studies and changes in compensation practices of our competitors; (ii) economic and market conditions; (iii) changes in our business operations; (iv) the executive officer's position, experience, length of service and performance; (v) Company performance; and (vi) the judgment of each member of the Compensation Committee based upon prior experiences with executive compensation matters.

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COMPENSATION DISCUSSION & ANALYSIS

Elements of Executive Compensation

The key components of our current compensation and benefits programs for our NEOs are summarized in the table below. Each component has a critical role in motivating and rewarding strong performance and retaining the NEOs who deliver such performance. The Compensation Committee considers each compensation component individually and all compensation components in the aggregate when making compensation decisions.

During 2024 and early 2025, the Compensation Committee undertook a review of the metrics included in the long-term incentive plan, considering input from its compensation consultant and the CEO and other senior management personnel. The Compensation Committee considered a variety of additional performance metrics and plan structures for the long-term incentive plan, after which it decided to replace certain operational-based metrics with an additional meaningful, financial performance metric and to adjust certain aspects of the relative TSR modifier. Specifically, the long-term incentive plan was modified to (i) incorporate a cumulative, three-year adjusted earnings per share performance metric in place of certain existing operational-based metrics (i.e., capital efficiency, fleet management, driver safety) and (ii) adjust the TSR modifier so that it can positively or negatively impact achievement percentage attained under the entire plan.

COMPENSATION DISCUSSION & ANALYSIS

The Compensation Committee adopted these changes to continue to align the plan with stockholder expectations and the Company's long-term strategic initiatives and with the objective of producing a simplified plan that focuses on incentivizing increased profitability and the creation of stockholder value over the longer term. Furthermore, the Compensation Committee believes the revised structure of the TSR modifier, which can apply either positively or negatively, values TSR performance that is significantly divergent from the overall applicable market index, thereby properly valuing both superior and substandard stock price performance. Lastly, the Compensation Committee believes that while the prior operational metrics remain important drivers of overall Company performance, they will continue to be reflected in the Company's overall financial performance, including with respect to adjusted earnings per share.

Executive Compensation Decisions for 2025

Base Salary

Base salary is a critical element of NEO compensation because it provides a base level of monthly income that compensates executives for their daily duties and responsibilities. Base salaries for NEOs are determined annually by the Compensation Committee during the first quarter of the fiscal year, taking into account such factors as competitive industry salaries (especially the salary practices of companies in our peer group described below in Compensation Process), a subjective assessment of the nature of the position, and the contributions, experience, level of responsibility and length of service of the NEO. During 2025, the Compensation Committee, after taking into account, among other things, the results of a peer review study performed by its compensation consultant, concluded to increase the base salary for Mr. Austin based on performance and to better align with the market data for his position. Additionally, the Compensation Committee approved increases to Ms. Desai's and Mr. Studer's base salaries to better align with the market data with respect to their positions and responsibilities, as well as based on their strong performance.

Annual Incentive Plan

Our annual incentive plan for senior leadership is designed to provide our NEOs with performance awards payable annually in recognition of Quanta achieving specified financial and safety performance targets, which are approved by the Compensation Committee at the beginning of the fiscal year. The Compensation Committee elects to pay such performance awards in cash.

Awards for an eligible NEO who begins employment during the performance year will be pro-ratedfrom the date of hire, unless otherwise determined by the CEO and with the approval of the Compensation Committee. Generally, an NEO must be employed by Quanta on the date any cash incentive compensation is paid, and otherwise forfeits any and all rights to such compensation. However, an NEO who ceases to be employed prior to the payment date has the potential to receive an award (or some portion thereof) pursuant to contractual provisions or as otherwise determined by the CEO (other than with respect to himself) and with approval of the Compensation Committee. See Executive Compensation - Potential Payments Upon Termination or Change in Control.

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COMPENSATION DISCUSSION & ANALYSIS

The payout for each NEO under the annual incentive plan is calculated as a percentage of such NEO's base salary (the "AIP Target Incentive"), which is then multiplied by the weighted achievement percentage associated with the Company performance metrics, as set forth in the following calculation:

The Compensation Committee, after taking into account, among other things, the results of a peer review study performed by its compensation consultant, recommendations from Mr. Austin (other than with respect to himself), and each NEO's position, experience, level of responsibility and length of service, established the target incentives under the 2025 annual incentive plan set forth below. Target percentages were unchanged from 2025 for each NEO.

Adjusted EBITDA Component

Calculation. The adjusted EBITDA component of the annual incentive plan, which accounts for 60% of a participant's annual incentive opportunity, is based on Quanta's achievement of annual adjusted EBITDA, defined for purposes of the annual incentive plan as operating income, plusamortization, depreciation and stock-based compensation, adjusted foroperational activities affecting net income that are not included in operating income ("AIP Adjusted EBITDA"). Additional adjustments to actual AIP Adjusted EBITDA may be considered and approved by the Compensation Committee, including but not limited to, acquired business results (net of acquisition and integration costs), fair value changes in contingent consideration liabilities associated with acquired businesses, impairments and other charges related to divested or discontinued businesses, foreign currency exchange rate fluctuations, unforecasted strategic initiatives and costs (e.g., business dispositions, restructuring initiatives), and other unforeseen, unusual or one-timeitems.

Rationale.Generally, short-term incentives motivate and reward achievement and performance of Quanta's annual financial and operational goals. The Compensation Committee believes this performance metric is a valuable measure of cash-based operating performance and encourages our NEOs to grow the Company's business, including through expanding and developing relationships with existing and potential customers and expanding service offerings in existing and adjacent markets. Further, when combined with the margin-based performance metric discussed below, NEOs are encouraged to ensure that such growth is profitable and does not include excessive risk.

Performance / Achievement.Performance with respect to this component is measured by comparing actual AIP Adjusted EBITDA for the performance year to a target amount of AIP Adjusted EBITDA, which was established based on the amount of AIP Adjusted

COMPENSATION DISCUSSION & ANALYSIS

EBITDA correlated with the midpoint of the Company's full-year 2025 earnings guidance, as announced during the first quarter of the year. Based upon the performance/payout scale adopted by the Compensation Committee for the 2025 performance year, NEOs could earn cash awards for this component of the annual incentive plan as follows (when performance falls between the designated payout points above the threshold amount, the cash awards are determined by interpolation):

The 2025 target amount of AIP Adjusted EBITDA represented an approximate 26.1% increase from actual AIP Adjusted EBITDA achieved in 2024. For the 2025 performance year, the Compensation Committee concluded that actual AIP Adjusted EBITDA was $2,787.0 million, which represents an achievement percentage of 142.2%. For a reconciliation of AIP Adjusted EBITDA to operating income for the year ended December 31, 2025 determined in accordance with GAAP, see Appendix Ato this Proxy Statement.

Adjusted EBITDA Margin Component

Calculation. The adjusted EBITDA margin component of the annual incentive plan, which accounts for 20% of a participant's annual incentive opportunity, is based on Quanta's achievement of annual targeted margin performance on the AIP Adjusted EBITDA earned by the Company. Adjusted EBITDA margin is measured as AIP Adjusted EBITDA, divided byconsolidated revenues (adjusted to exclude foreign currency exchange rate fluctuations and revenues attributable to businesses acquired during the performance year, as well as certain other unforecasted items, that were not included in the Company's full-year 2025 earnings guidance announced during the first quarter of the year) ("AIP Adjusted EBITDA margin").

Rationale.The Compensation Committee believes this performance metric is highly correlated with stockholder return and reinforces the Company's focus on margin improvement and profitable growth, which complements the AIP Adjusted EBITDA metric described above by penalizing management for focusing solely on revenue growth. The Compensation Committee also believes this metric complements the ROIC component included in the long-term incentive plan described below by rewarding the deployment of capital and resources in a manner that results in a profitable return.

Performance / Achievement.Performance with respect to this component is measured by actual AIP Adjusted EBITDA margin for the performance year as compared to a target margin, which was established based on the target amount of AIP Adjusted EBITDA set forth above relative to the range of the Company's full-year 2025 revenue guidance, as announced during the first quarter of the year. Based upon the performance/payout scale adopted by the Compensation Committee for the 2025 performance year, NEOs could earn cash awards for this component of the annual incentive plan as follows (when performance falls between the designated payout points above the threshold amount, the cash awards are determined by interpolation):

The 2025 target AIP Adjusted EBITDA margin represented an approximate 27 bps increase from actual AIP Adjusted EBITDA margin achieved in 2024. For the 2025 performance year, actual AIP Adjusted EBITDA margin was 10.06%, which was above the target level of performance, resulting in an achievement percentage of 129.7% for this component of the annual incentive plan. For a reconciliation of adjusted consolidated revenues to consolidated revenues determined in accordance with GAAP and a calculation of AIP Adjusted EBITDA margin for the year ended December 31, 2025, see Appendix Ato this Proxy Statement.

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COMPENSATION DISCUSSION & ANALYSIS

Safety Performance Component

Calculation. The final component of the annual incentive plan, which accounts for the remaining 20% of a participant's annual incentive opportunity, is based on the Company's achievement of a measurable safety performance goal. Performance with respect to this component is measured based on improvement with respect to the rate of incidence of significant safety events (e.g., life-altering and life-ending safety events) for the performance year as compared to performance with respect to such events in the prior year. Performance with respect to significant safety events is calculated through an internal safety predictive measure and is defined as the number of significant safety events in the performance year, multiplied by 1,000,000, and divided by the Company's total work hours for the applicable year.

Rationale. Generally, this goal aligns with the Company's strategic priority of a commitment to workforce safety and management's expectation that the Company will achieve industry-leading safety performance. The Compensation Committee determined that utilizing such a metric was an appropriate enhancement in evaluating the Company's overall safety performance, as a reduction of these events is a key operational focus of the Company and of the utmost importance to the overall safety of Quanta's employees. Furthermore, the Compensation Committee believes utilization of a metric relating to significant safety events is appropriate given the importance of preventing such events and that measuring these events can often provide greater insight into the overall safety performance of the Company than traditional safety metrics. A key strategic initiative of the Company has been to track and analyze significant safety events, and this internal predictive measure is aligned with the Company's overall Capacity Model for safety, which is designed to reduce such events by building in the capacity to fail safely when performing services that involve significant operational hazards. Therefore, the Compensation Committee believes that achievement of this goal has a significant positive impact on both short-term financial performance by reducing costs associated with safety incidents and long-term performance and sustainability, as safe performance impacts the Company's ability to maintain and increase its business with existing and potential customers and attract and retain employees.

Performance / Achievement. For 2025, threshold performance with respect to significant safety events was set based on improving upon the Company's performance from 2024, accounting for expectations for a continued increase in total workhours, and target performance was set based on relative improvement as compared to the threshold. Specifically, the NEOs could earn cash awards for this component of the annual incentive plan as follows (when performance falls between the designated payout points above the threshold amount, the cash awards are determined by interpolation):

For the 2025 performance year, the Company's performance with respect to significant safety events improved as compared to the 2024 performance year and was above threshold performance improvement in the achievement scale but below target performance established by the Compensation Committee. As a result, the overall achievement percentage was 77.9%.

Overall Performance and Payout

Overall performance based on the weighted results set forth above resulted in a total achievement percentage of 126.8%, and therefore the total payout to each NEO under the 2025 annual incentive plan was as follows:

COMPENSATION DISCUSSION & ANALYSIS

Long-Term Incentive Plan

Our long-term incentive plan for senior leadership is designed to provide our NEOs with long-term incentive awards payable in equity. The targeted incentive amount for each NEO under the long-term incentive plan is determined annually by the Compensation Committee ("Long-Term Target Incentive"). The Compensation Committee approved the following Long-Term Target Incentives for 2025 after taking into account, among other things, the results of a peer data study performed by its compensation consultant, recommendations from Mr. Austin (other than with respect to himself), each NEO's position, experience, level of responsibility and length of service, and with respect to Mr. Ducey to align with market data for his position:

Generally, an NEO must be employed by Quanta on the date an award vests or is earned under the long-term incentive plan or otherwise forfeits any and all rights to such award. However, an NEO who ceases to be employed prior to the completion of the 3-yearperformance period described below has the potential to receive an award (or some portion thereof) pursuant to contractual provisions or as otherwise determined by the Chief Executive Officer (other than with respect to himself) and with approval of the Compensation Committee. See Executive Compensation - Potential Payments Upon Termination or Change in Control.Awards for an NEO who becomes a participant in the long-term incentive plan during the performance period are pro-ratedfrom the date of hire; however, in any event, an NEO must be employed by October 1st of the first year of the 3-yearperformance period to be eligible to participate.

PSU Component

The first component of the long-term incentive plan, which accounts for 60% (or with respect to Messrs. Austin and Studer, 70%) of an NEO's Long-Term Target Incentive, consists of PSUs that are eligible to cliff vest at the end of a 3-yearperformance period based on achievement of 3-yearCompany performance goals determined by the Compensation Committee (the "Long-Term PSU Component") and continued employment. Under the 2025 long-term incentive plan, the Compensation Committee approved the following PSU awards:

Though PSUs representing the Long-Term PSU Component target amount were granted to the NEOs in 2025, the number that will ultimately be earned and vest will be adjusted upward or downward (as applicable) based on Company performance during the 3-yearperformance period ending December 31, 2027. The number of PSUs that can become earned at the end of the performance period ranges from 0% to a maximum of 215% of the amount granted. Any earned PSUs will vest immediately after the Compensation Committee's determination of the extent to which the performance metrics were attained and will be settled in Quanta common stock. Quanta also accrues for dividend equivalents on PSUs at the same time and at the same rate as dividends are paid on Quanta common stock; however, payment of dividend equivalents on shares underlying unearned and unvested PSUs is expressly prohibited until the PSUs become earned and vest, such that the declared dividend equivalents are subject to forfeiture unless and until the PSUs to which they relate vest.

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COMPENSATION DISCUSSION & ANALYSIS

In connection with its ongoing review of executive compensation, and as described in further detail in Elements of Executive Compensation, the Compensation Committee determined that it was appropriate to adjust the metrics included in the Long-Term PSU Component to simplify the overall structure of the long-term incentive plan and to increase focus on continued earnings growth, as a complement to effective deployment of capital. With that in mind, for the 3-yearperformance period ending December 31, 2027, the Compensation Committee established Company performance goals relating to (i) improvement of ROIC (which accounts for 60% of the number of PSUs that each NEO can earn); (ii) cumulative adjusted earnings per share (which accounts for 40% of the number of PSUs that each NEO can earn); and (iii) a relative TSR performance modifier (which can increase or decrease the overall achievement percentage by 15%). The ROIC and cumulative adjusted earnings per share goals have a 0% to 200% performance scale, which can then be increased or decreased by the TSR modifier. The performance targets and results for these goals may be adjusted, as appropriate, to take into account any unusual or unforeseen events that occur during the performance period.

As soon as administratively practicable following the conclusion of the 3-yearperformance period on December 31, 2027, the weighted percentage earned for each goal will be determined, and the combined weighted percentage earned will then be multiplied by the number of PSUs granted in 2025. This will result in a final number of earned and vested PSUs, which will be settled in shares of Quanta common stock, as set forth in the following calculation:

ROIC Improvement Performance Goal

For the ROIC performance goal, which accounts for 60% of the PSU component, the Compensation Committee established targeted amounts that reward overall ROIC improvement during the 3-yearperformance period.

Rationale.The Compensation Committee believes that measuring improvement in ROIC is appropriate to assess the Company's ability to create incremental return and value on all of its invested capital and determined that utilizing a 3-yearaverage of annual ROIC performance will appropriately measure and reward improved performance. The Compensation Committee believes this performance metric requires both income statement and balance sheet management and that achievement of the targeted ROIC will have a significant positive impact on both long-term financial performance and stockholder value creation and exhibit appropriate capital allocation priorities.

Calculation.Performance with respect to the ROIC improvement goal is measured based on average ROIC during the 3-yearperformance period. ROIC for each year is calculated as net operating profit after tax,divided byaverage invested capital. Net operating profit after tax is equal to adjusted EBITA, multiplied by(1 - tax rate), less non-controllinginterests (after tax). Average invested capital is equal to total assets, minus non-controllinginterests, cash and non-interestbearing current liabilities and is taken as the average of the current year-endand the prior year-end.

For purposes of calculating ROIC, (i) net operating profit after tax may be adjusted by the same adjustments described above with respect to AIP Adjusted EBITDA, subject to the discretion of the Compensation Committee, except that there is no adjustment for acquisitions unless otherwise determined by the Compensation Committee, and (ii) invested capital is subject to the balance sheet impact of those same adjustments, as applicable and as deemed appropriate by the Compensation Committee.

COMPENSATION DISCUSSION & ANALYSIS

Performance / Achievement.With respect to average ROIC during the performance period, a payout begins to accrue only if average ROIC is greater than a threshold amount, which is aligned with the Compensation Committee's and management's expectations with respect to the level of ROIC performance that the Company should achieve to consistently create value. Performance above threshold / at target represents return in excess of the Company's cost of capital and performance at maximum represents consistent improvement over historical performance. The Compensation Committee established the following performance/payout scale for assessing average ROIC improvement (average ROIC will be rounded to the nearest one tenth decimal place):

Additionally, consistent performance during a majority of the 3-yearperformance period can result in a moderated payout. Namely, if two annual measurements result in ROIC greater than the threshold amount, but 3-yearaverage ROIC fails to achieve the threshold average improvement, the Compensation Committee determined an achievement percentage of 66% would be warranted.

Cumulative Adjusted Earnings Per Share Goal

For the cumulative adjusted EPS goal, which accounts for 40% of the number of PSUs that each NEO can earn, the Compensation Committee established targeted amounts that reward cumulative adjusted EPS improvement during the 3-yearperformance period.

Rationale.The Compensation Committee believes this cumulative adjusted EPS metric is an appropriate complementary measure for overall ROIC. While improved ROIC targets efficient utilization of all of the Company's invested capital, this metric focuses on continued profitability and earnings growth over the 3-yearperformance period, incentivizing management to grow the Company without taking excessive risk. Measurement of performance with respect to this metric allows the Compensation Committee to evaluate whether management is successfully performing against its core strategic objective to ensure earnings growth, and when combined with performance under the ROIC performance metric, provides a complete picture of the Company's profitability and capital management.

Calculation.Performance with respect to the cumulative adjusted EPS improvement goal is measured based on adjusted EPS during the 3-yearperformance period. The calculation for adjusted EPS aligns with the calculation utilized with respect to the Company's financial reporting, which includes adjustments to GAAP diluted EPS for, among other items, acquisition and integration costs, fair value of contingent consideration liabilities, gain/loss on sale of investments or businesses, foreign currency translation losses, non-cashstock-based compensation and amortization, minus the tax impact of these adjustments and the impact of tax contingency releases.

Performance / Achievement.A payout begins to accrue only if cumulative adjusted EPS is greater than a threshold amount, which is established based on significant improvement from the prior year actual results. Furthermore, target performance corresponds to the expected level of earnings per share growth from the baseline amount during the 3-yearperformance period, and performance above the target amount represents a significant improvement above the target amount. Based on the considerations above, the Compensation Committee established the performance/payout scale below for the targeted cumulative adjusted EPS. When attainment of the goal falls between the designated percentages in the table, the percentage of target incentive earned is determined by interpolation.

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COMPENSATION DISCUSSION & ANALYSIS

Relative TSR Modifier

Rationale. The Compensation Committee believes that a relative TSR modifier creates strong alignment with stockholder interests and the Company's strategic growth. The Compensation Committee also determined that TSR performance should only be rewarded or penalized based on performance that diverges significantly from the median, which can be indicative of the investment community's evaluation of management performance.

Calculation. Relative TSR performance is calculated based on the Company's performance relative to companies within a broad equity market index, namely the S&P 500 Industrials Index, for each of the twelve quarters during the 3-yearperformance period. For 2025, the Compensation Committee determined that the S&P 500 Industrials Index was an appropriate index to utilize due to the fact that the companies included in that index are aligned with Quanta's current market capitalization and include more of Quanta's industry peers.

TSR for the Company is calculated each quarter by determining the percentage appreciation or depreciation of stock price (utilizing the average closing price for the twenty consecutive trading days prior to the end of quarter), plus the value of dividends paid during the quarter. The Company's performance relative to the individual companies within the S&P 500 Industrials Index is established at the end of each quarterly period by evaluating performance from the beginning of the performance period (i.e., January 1, 2025) through that quarter end. The highest and lowest percentile ranks are then set aside, and the remaining ten percentile ranks are averaged to determine the Company's final average percentile rank. The Compensation Committee believes this calculation of TSR prevents the overweighting of anomalous events at the beginning or end of the measurement period, whether they be positive or negative. The Compensation Committee also believes that quarterly evaluations are aligned with how stockholders evaluate management with respect to stockholder value creation.

Performance / Achievement.If the Company's average relative TSR is in the 90th percentile or above of the S&P 500 Industrials Index, the overall achievement percentage under the Long-Term PSU Component will be increased by 15%. The Compensation Committee believes this is the appropriate level of performance to justify a payout under this metric. If the Company's average relative TSR falls between the 10th percentile and the 90th percentile, no adjustment will be made to the overall achievement percentage, and if the Company's average relative TSR is within the 10th percentile or below, the overall achievement percentage under the Long-Term PSU Component will be reduced by 15%.