Comfort Systems USA (FIX) 10-K risk factor changes: FY2025 vs FY2024

Our business, financial condition, results of operations [removed: or] [added: and] cash flows could be adversely affected by the occurrence of any of these events, which could cause actual results to differ materially from expected and historical results, and the trading price of our common stock could decline.

We experience the results of economic trends well after an economic cycle [removed: begins,] [added: begins] and therefore have generally continued to experience the results of an economic recession well after conditions in the general economy have improved.

The industries and markets in which we operate have [removed: always] been and will continue to be vulnerable to macroeconomic downturns because they are cyclical in nature.

Further, to the extent some of our vendors, subcontractors, developers, or general contractors seek bankruptcy protection, [removed: such bankruptcy] [added: we] will likely [removed: force us to] incur additional [removed: costs in] attorneys’ [removed: fees, as well as] [added: fees and] other professional [removed: consultants,] [added: consultant fees] and [added: expenses in connection with pursuing payment in such bankruptcy proceedings, and such increased expenses] will [added: likely] result in decreased revenue and profit.

Additionally, because [removed: 5.4%] [added: 5.0%] of our revenue for the year ended December 31, [removed: 2024] [added: 2025] was attributable to projects in the government sector, a reduction in federal, state, or local government spending in our industries and markets could [removed: result in decreased revenue] [added: have an adverse effect on our business, financial condition, results of operations] and [removed: profit for us.][added: cash flows.]

Our contract prices are established largely based on estimates and assumptions [removed: of] [added: regarding] our projected costs, including assumptions about: future economic conditions; prices, including commodity prices and inflation; availability of labor, including the costs of providing labor, equipment, and materials; and other factors outside our control.

Our backlog as of December 31, [removed: 2024] [added: 2025] was [removed: $5.99] [added: $11.94] billion.

[removed: These conditions have] [added: The global economy has recently experienced high rates of inflation, which] increased our [removed: cost] [added: costs] for labor, materials, [removed: utilities,] [added: utilities] and other goods and services.

Further, there are [removed: market] concerns that the United States economy could experience a recession.

As a result, these conditions have, and they or any similar future conditions may continue to have, [removed: significant] [added: an] adverse [removed: impacts] [added: effect] on our business, financial [removed: condition and] [added: condition,] results of [removed: operations.][added: operations and cash flows.]

The loss of one or a few customers could adversely affect our business, financial [removed: condition and] [added: condition,] results of [removed: operations.][added: operations and cash flows.]

A [removed: few] [added: limited number of] customers have in the past and may in the future account for a significant portion of our [removed: revenues.][added: revenue.]

For example, in [removed: 2024,] [added: 2025,] one customer represented approximately [removed: 13.3%] [added: 12.8%] of our consolidated revenue.

[added: Although we have] long \- standing relationships with many of our significant customers and believe that our portfolio of customers is reasonably diverse, one or [removed: a number] [added: more] of [added: our] significant customers may [removed: unilaterally] reduce, fail to renew, or terminate their contracts with us in the future.

Rising [removed: inflation and/or] [added: inflation,] interest [removed: rates] [added: rate volatility and an economic recession or downturn] may have an adverse effect on our business, financial [removed: condition and] [added: condition,] results of [removed: operations.][added: operations, and cash flows.]

In [removed: efforts] [added: order] to combat inflation, the U.S. Federal Reserve raised interest rates multiple times in recent years and may do so again in [removed: 2025] [added: 2026] (or may slow any rate reductions from what the market currently anticipates).

Economic factors, including inflation and [removed: fluctuations in] interest [removed: rates,] [added: rate volatility,] may have a negative impact on our business.

[removed: Furthermore, the] [added: The] cost of our materials, labor, [added: utilities] and [added: other goods and] services may [added: continue to] rise as a result of [removed: continued] inflation and [removed: further] interest rate hikes, and we may not be able to offset such higher costs through price increases.

While we believe our customers consider a number of these factors in awarding [removed: available] contracts, a large portion of our work is awarded through a bid process.

We expect to continue [removed: pursuing] [added: to pursue] selective acquisitions of businesses.

| | ● | we may not be able to realize the cost [removed: savings or] [added: savings,] other financial benefits [added: or synergies] we anticipated prior to the acquisition. |

The failure to successfully integrate acquisitions could have an adverse effect on our business, financial [removed: condition and] [added: condition,] results of [removed: operations.][added: operations, and cash flows.]

Increases in such labor costs for a prolonged period of time could have a material adverse effect on [removed: the company’s] [added: our business,] financial [removed: condition and] [added: condition,] results of [removed: operations.][added: operations, and cash flows.]

We have determined in the past and may again determine in the future that a significant impairment has occurred in the value of our unamortized intangible [removed: assets or fixed] assets, which could require us to write off a portion of our assets and could [removed: adversely affect] [added: have an adverse effect on] our financial condition [removed: or our reported] [added: and] results of operations.

In the past we have [removed: expanded,] [added: been required to increase,] and it is possible we will [removed: continue] [added: in the future be required] to [removed: expand,] [added: increase,] the number and percentage of total contract dollars [removed: that require] [added: for which we utilize] an underlying [added: surety] bond.

[removed: Historically, surety] market conditions have experienced times of [removed: difficulty] [added: volatility] as a result of significant losses incurred by many surety companies and the results of macroeconomic trends outside of our control, such as [removed: the current] volatility in the capital markets and the possibility of an extended economic downturn or recession.

Consequently, during times when less overall bonding capacity is available in the market, surety [added: terms have become more expensive and more restrictive.]

If we are [removed: not able] [added: unable] to maintain a sufficient level of bonding capacity in the future, it could preclude our ability to bid for certain contracts or successfully contract with some customers.

If a customer defaults in making their payments on a project to which we have devoted resources, it could have a material [removed: negative] [added: adverse] effect on our [added: business,] financial [removed: condition and] [added: condition,] results of [removed: operations.][added: operations and cash flows.]

Extreme weather conditions (such as storms, droughts, extreme heat or cold, wildfires and floods) may limit the availability of resources, increase our costs, or may cause projects to be [added: delayed or] cancelled.

If we are unable to manage the conditions required for certain of our jobs, including the availability of sufficient labor, adherence to environmental, health and safety or other standards, and adequately addressing harsh or hazardous conditions, our [removed: business and] [added: business,] financial [removed: condition] [added: condition, results of operations, and cash flows] could be [added: materially and] adversely affected.

Moreover, our business may be adversely affected by severe weather in areas where we have significant [removed: operations.][added: operations, which could have a material adverse effect on our financial condition, results of operations, and cash flows.]

[removed: Legislation, nationwide protocols,] [added: Evolving legislation, foreign and domestic policy,] regulation or other restrictions related to climate change could negatively impact our operations or our customers’ operations.

[removed: Increasing] [added: Diverging] concerns about climate change and other environmental issues may result in [removed: additional] [added: varying] environmental regulations and [removed: restrictions.][added: restrictions on our operations.]

Compliance with more stringent laws or regulations, as well as more vigorous enforcement policies of the [added: federal, state, or local] regulatory agencies, could increase the costs of projects for our customers or, in some cases, prevent a project from going forward, which could in turn have [removed: an] [added: a material] adverse effect on our [added: business,] financial [removed: condition and] [added: condition,] results of [removed: operations.][added: operations and cash flows.]

Continuing worldwide political and economic uncertainties may adversely affect our [removed: revenue] [added: business, financial condition, results of operations,] and [removed: profitability.][added: cash flows.]

The last several years have been [removed: periodically] marked by [added: worldwide] political and economic [removed: concerns,] [added: uncertainty resulting from a number of factors,] including [removed: the COVID-19 pandemic,] decreased consumer confidence, the effects of international conflicts such as the wars between Russia and Ukraine and unrest in the Middle East, [added: supply chain disruptions,] tariffs, [added: rising] energy costs and inflation.

This [removed: instability can make] [added: uncertainty has made (and may continue to make)] it extremely difficult for our customers, [removed: our] vendors and us to accurately forecast and plan future business activities, and could [removed: cause] [added: lead to] constrained spending on our services, delays and a lengthening of our business development efforts, the demand for more favorable pricing or other terms, and/or difficulty in collection of our accounts receivable.

Further, ongoing [added: political and] economic instability [removed: in the global markets,] [added: has caused (and could continue to cause)] supply chain [removed: disruptions, rising inflation and interest rates and the wars between Russia and Ukraine] [added: disruptions] and [removed: unrest] [added: volatility] in the [removed: Middle East, could] [added: capital markets, which may increase our costs of capital and] limit our ability to access the capital markets at a time when we would like, or need, to raise [removed: capital, which could have an impact on our ability to react to changing business conditions or new opportunities.][added: capital.]

Labor shortages, including the recent U.S. labor shortage, increased labor costs or the loss of key personnel [removed: may reduce] [added: could have a material adverse effect on] our [removed: profitability] [added: business, financial condition, results of operations,] and [removed: negatively impact our business.][added: cash flows.]

Moreover, if we do not employ new technologies as quickly or efficiently as our competitors, or if our competitors develop or utilize more cost-effective or customer-preferred technologies (such as data analytics, artificial intelligence and other new and emerging technologies) that give them a competitive advantage in the proposal bidding and selection process, it could have a material adverse effect on our ability to win and retain business from customers.

Historically, surety

Operating in a number of jurisdictions could make our compliance with laws relating to climate change rules more complex and expensive and potentially expose us to greater levels of legal risks associated with our compliance.

Our failure to comply with any applicable laws could lead to penalties and adversely impact our reputation, customer attraction and retention, access to capital and employee retention.

These conditions could have a material adverse effect on our business, financial conditions, results of operation and cash flows.

However, this

We and certain of our third-party providers collect and retain information about our customers, stockholders, vendors and employees, including information about individuals, as well as proprietary information belonging to our business (collectively, “Confidential Information”).

We face numerous and evolving cybersecurity risks that threaten the confidentiality, integrity and availability of our IT Systems and Confidential Information, including from diverse threat actors, such as state-sponsored organizations, opportunistic hackers and hacktivists, as well as through diverse attack vectors, such as social engineering/phishing, malware (including ransomware), malfeasance by insiders, human or technological error (including the misuse of artificial intelligence tools by our employees), and as a result of malicious code embedded in open-source software, or misconfigurations, bugs or other vulnerabilities in commercial software that is integrated into our (or our suppliers’ or service providers’) IT Systems, products or services.

Because we make extensive use of third-party suppliers and service providers, such as cloud services that support our internal and customer-facing operations, successful cyberattacks that disrupt or result in unauthorized access to third party IT Systems can materially impact our operations and financial results.

Remote and hybrid working arrangements at the Company (and at many third-party providers) also increase cybersecurity risks due to the challenges associated with managing remote computing assets and security vulnerabilities that are present in many non-corporate and home networks.

Additionally, any integration of artificial intelligence in our or any service providers’ operations, products or services is expected to pose new or unknown cybersecurity risks and challenges.

Any circumvention or failure of our cybersecurity defenses or measures could compromise the confidentiality, integrity, and availability of our customers’ own IT Systems and/or Confidential Information as well.

Moreover, cyberattacks are expected to accelerate on a global basis in frequency and magnitude as threat actors are becoming increasingly sophisticated in using techniques and tools—including artificial intelligence to engage in automated, targeted, and coordinated attacks—that circumvent security controls, evade detection and remove forensic evidence.

As a result, we may be required to expend significant resources to protect

In addition, our IT Systems could be damaged or interrupted by natural disasters, power loss, or telecommunications failures.

projects and increase our overall risk exposure.

We also may be required to indemnify third parties for litigation brought against such third parties, even if we are not a defendant.

Changes in U.S. foreign relations, in particular foreign trade policies could lead to the imposition of additional trade barriers and tariffs.

We cannot predict the full extent of new, extended, or changed trade policies, including tariffs, that may be made by the current or a future presidential administration or Congress, including whether existing tariff policies will be maintained or modified or if changes in the U.S. trade policy could result in reactions from U.S. trading partners, such as adopting responsive trade policies making it more difficult or costly for us to purchase materials or supplies.

These changes in U.S. trade policy or in laws and policies governing foreign trade or foreign relations generally, and any resulting negative sentiments towards the United States as a result of such changes, could have an adverse impact on our business, financial condition, results of operations, and cash flows.

Our accounting for income taxes requires significant judgments and may be impacted by changes to our assessment of our projected tax liability, including our ability to realize deductions or credits in various tax jurisdictions.

Moreover, we may be affected by our ability to utilize, or in the valuation of, our deferred tax assets that are based on estimates of our future results, the prudence and feasibility of possible tax planning strategies, and the economic and political environments in which we do business.

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or costly.

​

Such changes may adversely affect the revenues and profit we ultimately realize on these projects.

We could be adversely impacted by the effects of inflation, supply chain disruptions, capital market volatility and an economic recession or downturn.

The global economy continues to experience high rates of inflation and market and economic volatility, resulting from a number of factors, including the war between Russia and Ukraine, unrest in the Middle East, and supply chain constraints.

In addition, the current market conditions have caused volatility in the capital markets, which may increase our cost of capital or prevent us from raising capital if we desire or need to do so and may have adverse impacts on the mechanical and electrical services industry.

Although we have

Our inability or failure to do so could harm our financial position and results of operations.

terms have become more expensive and more restrictive.

If economic conditions remain uncertain or weaken, or government spending is reduced, our revenue and profitability could be adversely affected.

We also collect and retain information about our customers, stockholders, vendors and employees, with the expectation by such third parties being that we will adequately protect such information.

In addition, our systems, networks and infrastructure could be damaged or interrupted by natural disasters, power loss, telecommunications failures, intentional or inadvertent user misuse or error, failures of information technology solutions, computer viruses, malicious code, ransomware attacks and acts of terrorism.

We may also be subject to physical or electronic security breaches, including breaches by computer hackers or cyber-terrorists or unauthorized access to or disclosure of our or our customers’ data.

While we have security, internal control and technology measures in place to protect our systems and networks, these measures could fail as a result of a cyber-attack, other third-party action, employee error, malfeasance or other security failure.

In the ordinary course of business, we have been targeted by malicious cyber-attacks.

As cybersecurity threats continue to evolve, we may be required to expend significant additional resources to continue to modify or enhance our protective measures or to investigate and remediate any information security vulnerabilities.

The inability to implement, maintain and upgrade adequate safeguards could have a material adverse effect on our business.

New cyber-related regulations, including the cybersecurity risk management, strategy, governance and incident disclosure rules adopted by the SEC in 2023, or other requirements could require significant additional resources and cause us to incur significant costs, which could have an adverse effect on our results of operations and cash flows.

If we are unable to

The costs of employee health insurance have been increasing in recent years due to rising healthcare costs, legislative changes, and general economic conditions.

Additionally, we may incur additional costs as a result of the Patient Protection and Affordable Care Act (the “Affordable Care Act”) that was signed into law in March 2010.

Future legislation could also have an impact on our business, including potential healthcare reform efforts under the Trump administration, the nature and impact of which are uncertain.

The status of the Affordable Care Act, any amendment, repeal or replacement thereof, is currently uncertain.

For example, in December 2019, the United States Court of Appeals for the Fifth Circuit struck down a central provision of the Affordable Care Act, ruling that the requirement that people have health insurance was unconstitutional, sending the case back to a federal district judge in Texas to determine which of the law’s many parts could survive without the mandate.

On March 2, 2020, the United States Supreme Court granted certiorari to review this case, and on June 17, 2021, the U.S. Supreme Court dismissed a challenge on procedural grounds that argued the Affordable Care Act is unconstitutional in its entirety because the “individual mandate” was repealed by Congress.

The Affordable Care Act will remain in effect in its current form; however, we continue to evaluate the effect that the Affordable Care Act has on our business.

Costs incurred as a result of warranty claims could adversely affect our operating results and financial condition.

Changes in United States trade policy, including the imposition of tariffs and the resulting consequences, may have a material adverse impact on our business and results of operations.

As a result of policy changes or shifting proposals by the U.S. government, there may be greater restrictions and economic disincentives on international trade.

For example, the U.S. government has adopted an evolving approach to trade policy, including renegotiating or terminating certain existing bilateral or multi-lateral trade agreements.

It has also imposed tariffs on certain foreign goods and raised the possibility of imposing significant, additional tariff increases or expanding the tariffs to capture other types of goods.

These tariffs and other changes in U.S. trade policy have in the past and could continue to trigger retaliatory actions by affected countries, and certain foreign governments have instituted or are considering imposing retaliatory measures on certain U.S. goods.

If we are unable to pass the costs of such tariffs on to our customer base or otherwise mitigate such costs, or if demand for our services decreases due to the higher cost, our results of operations could be materially adversely affected.

In response to Russia’s invasion of Ukraine in 2022, the United States and other countries imposed trade sanctions against Russia and Belarus, which impacted global operations and financial performance.

We, our suppliers and our customers import certain raw materials, components and other products from foreign suppliers.

As such, the adoption and expansion of trade restrictions such as those adopted in response to Russia’s invasion of Ukraine, the occurrence of a trade war, or other governmental action related to tariffs or trade agreements or policies has in the past and may continue to adversely impact demand for our services, our costs, our customers, our suppliers, and the United States economy, which in turn could have an adverse effect on our business, financial condition and results of operations.

Significant judgment is required in our accounting for income taxes.

Issues relating to tax audits or examinations and any related interest or penalties and uncertainty in obtaining deductions or credits claimed in various jurisdictions could also impact the accounting for income taxes.

jurisdictions.

events in private client contracts and review and attempt to mitigate force majeure events in both public and private client contracts.

We operate primarily in the commercial, industrial and institutional markets and perform most of our work in manufacturing, healthcare, education, [added: office, technology, retail and government facilities.]

In our mechanical business segment, customers hire us to ensure [removed: HVAC] [added: heating, ventilation and air conditioning (“HVAC”)] systems deliver specified or generally expected heating, cooling, conditioning and circulation of air in a facility.

In our electrical business segment, our principal business activity is electrical construction and engineering in the commercial and industrial [removed: field.][added: fields.]

Approximately [removed: 91.1%] [added: 92.7%] of our revenue is earned on a project basis for installation services in newly constructed facilities or for replacement of systems in existing facilities.

When competing for project business, we usually estimate the costs we will incur on a [removed: project,] [added: project] and then propose a bid to the customer that includes a contract price and other performance and payment terms.

As of December 31, [removed: 2024,] [added: 2025,] we had [removed: 7,935] [added: 8,427] projects in process.

Our average project takes six to nine months to complete, with an average contract price of approximately [removed: $1.8] [added: $2.9] million.

We have what we consider to be a well-diversified distribution of revenue across end-use sectors that we believe reduces our exposure to negative [added: developments in any given sector.]

Taken together, projects with contract prices of $2 million or more totaled [removed: $12.78] [added: $22.44] billion of aggregate contract value as of December 31, [removed: 2024,] [added: 2025,] or approximately [removed: 89%,] [added: 93%,] out of a total contract value for all projects in progress of [removed: $14.35] [added: $24.17] billion.

A stratification of projects in progress as of December 31, [removed: 2024,] [added: 2025,] by contract price, is as follows:

| ​ | [added: ​ ​ ​] | ​ | [added: ​ ​ ​] | Aggregate | | |

| Contract Price of Project | ​ | Projects | ​ | [removed: (millions)] [added: (in millions)] | | |

| $10 million - $20 million | | [removed: 138] [added: 194] | ​ | | [removed: 1,947.4] [added: 2,751.1] | ​ |

| $20 million - $40 million | | [removed: 114] [added: 140] | ​ | | [removed: 3,253.0] [added: 3,936.7] | ​ |

| Greater than $40 million | | [removed: 68] [added: 119] | ​ | | [removed: 4,343.3] [added: 11,122.4] | ​ |

In addition to project work, approximately [removed: 8.9%] [added: 7.3%] of our revenue represents maintenance and repair service on already installed HVAC, electrical, and controls systems.

We also provide maintenance and repair [removed: service] [added: services] under ongoing contracts.

These agreements typically are for one or more years and frequently contain [removed: thirty-] [added: 30-] to [removed: sixty-day] [added: 60-day] cancellation notice periods.

We manage our [removed: 47] [added: 50] operating units based on a variety of factors.

[removed: Accordingly,] we devote considerable attention to operating unit management quality, stability, and contingency planning, including related considerations of compensation and non-competition protection where applicable.

We [removed: experienced increasing demand in 2022, 2023 and 2024 and we] [added: currently] expect that the demand environment, especially for manufacturing and technology customers, will remain at high levels [removed: leading into 2025.][added: during 2026.]

[removed: While the impacts from the supply chain shortages have improved,] [added: We experienced an unprecedented demand environment in 2025, and] we continue to experience increased labor costs and [added: intermittent supply chain shortages, including] delays in delivery of certain materials and equipment.

We have a credit facility in place with terms we believe are favorable that does not expire until [removed: July 2027.][added: October 2030.]

As of December 31, [removed: 2024,] [added: 2025,] we had [removed: $770.0] [added: $921.0] million of credit available to borrow under our credit facility.

We have generated positive free cash flow in each of the last [removed: twenty-six] [added: 27] calendar years and will continue our emphasis in this area.

| ​ | ​ | [removed: 2024] [added: 2025] | | | | [added: ​ ​ ​] | [removed: 2023] [added: 2024] | | | | [added: ​ ​ ​] | [removed: 2022] [added: 2023] | | | | ​ |

| Revenue | ​ | $ | [removed: 7,027,476] [added: 9,101,641] | [added: ​ ​ ​] | 100.0 | % | $ | [removed: 5,206,760] [added: 7,027,476] | [added: ​ ​ ​] | 100.0 | % | $ | [removed: 4,140,364] [added: 5,206,760] | [added: ​ ​ ​] | 100.0 | % |

| Cost of services | ​ | | [removed: 5,551,065] [added: 6,905,742] | | [removed: 79.0] [added: 75.9] | % | | [removed: 4,216,251] [added: 5,551,065] | | [removed: 81.0] [added: 79.0] | % | | [removed: 3,398,756] [added: 4,216,251] | | [removed: 82.1] [added: 81.0] | % |

| Gross profit | ​ | | [removed: 1,476,411] [added: 2,195,899] | | [removed: 21.0] [added: 24.1] | % | | [removed: 990,509] [added: 1,476,411] | | [removed: 19.0] [added: 21.0] | % | | [removed: 741,608] [added: 990,509] | | [removed: 17.9] [added: 19.0] | % |

| Selling, general and administrative expenses | ​ | | [removed: 730,072] [added: 883,284] | | [removed: 10.4] [added: 9.7] | % | | [removed: 574,423] [added: 730,072] | | [removed: 11.0] [added: 10.4] | % | | [removed: 489,344] [added: 574,423] | | [removed: 11.8] [added: 11.0] | % |

| Gain on sale of assets | ​ | | [removed: (3,030)] [added: (1,974)] | | — | ​ | | [removed: (2,302)] [added: (3,030)] | | — | ​ | | [removed: (1,585)] [added: (2,302)] | | — | ​ |

| Operating income | ​ | | [removed: 749,369] [added: 1,314,589] | | [removed: 10.7] [added: 14.4] | % | | [removed: 418,388] [added: 749,369] | | [removed: 8.0] [added: 10.7] | % | | [removed: 253,849] [added: 418,388] | | [removed: 6.1] [added: 8.0] | % |

| Interest income | ​ | | [removed: 11,554] [added: 21,604] | | 0.2 | % | | [removed: 3,492] [added: 11,554] | | [removed: 0.1] [added: 0.2] | % | | [removed: 46] [added: 3,492] | | [removed: —] [added: 0.1] | [removed: ​] [added: %] |

| Interest expense | ​ | | [removed: (6,648)] [added: (9,009)] | | (0.1) | % | | [removed: (10,281)] [added: (6,648)] | | [removed: (0.2)] [added: (0.1)] | % | | [removed: (13,352)] [added: (10,281)] | | [removed: (0.3)] [added: (0.2)] | % |

| Changes in the fair value of contingent earn-out obligations | ​ | | [removed: (88,146)] [added: (33,473)] | | [removed: (1.3)] [added: (0.4)] | % | | [removed: (23,607)] [added: (88,146)] | | [removed: (0.5)] [added: (1.3)] | % | | [removed: (4,819)] [added: (23,607)] | | [removed: (0.1)] [added: (0.5)] | % |

| Other income [added: (expense)] | ​ | | [removed: 432] [added: (258)] | | — | ​ | | [removed: 202] [added: 432] | | — | ​ | | [removed: 134] [added: 202] | | — | ​ |

| Income before income taxes | ​ | | [removed: 666,561] [added: 1,293,453] | | [removed: 9.5] [added: 14.2] | % | | [removed: 388,194] [added: 666,561] | | [removed: 7.5] [added: 9.5] | % | | [removed: 235,858] [added: 388,194] | | [removed: 5.7] [added: 7.5] | % |

| Provision [removed: (benefit)] for income taxes | ​ | | [removed: 144,128] [added: 270,895] | ​ | ​ | ​ | | [removed: 64,796] [added: 144,128] | ​ | ​ | ​ | | [removed: (10,089)] [added: 64,796] | ​ | ​ | ​ |

| Net income | ​ | $ | [removed: 522,433] [added: 1,022,558] | ​ | ​ | ​ | $ | [removed: 323,398] [added: 522,433] | ​ | ​ | ​ | $ | [removed: 245,947] [added: 323,398] | ​ | ​ | ​ |

We had [removed: 44] [added: 50] operating locations as of December 31, [removed: 2023.][added: 2025.]

| Under $2 million | | 6,759 | ​ | $ | 1,723.7 | ​ |

| $2 million - $10 million | | 1,215 | ​ | | 4,631.8 | ​ |

| Total | | 8,427 | ​ | $ | 24,165.7 | ​ |

Accordingly,

We have experienced increasing demand since 2022, culminating in an unprecedented overall demand environment in 2025.

Over the last several years, we have also experienced increases in labor costs and delays in delivery of certain materials and equipment.

We anticipate that cost pressures and intermittent delays in our supply chain will persist over the next several quarters.

2025 Compared to 2024

In the first quarter of 2025, we completed the acquisition of Century Contractors, LLC (“Century”), which reports as a separate operating location.

Additionally, we completed the acquisition of Right Way Plumbing & Mechanical LLC (“Right Way”), which reports as a separate operating location.

_Revenue_—Revenue increased $2.07 billion, or 29.5%, to $9.10 billion in 2025 compared to 2024.

| ​ | ​ ​ ​ | 2025 | | | | ​ ​ ​ | ​ | 2024 | | | | ​ ​ ​ |

Of this increase, $66.8 million resulted from the acquisition of Feyen Zylstra and Meisner, and $861.2 million was attributable to same-store activity.

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | | ​ | | ​ | | |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

The sequential backlog increase included the acquisitions of Feyen Zylstra ($90.9 million) and Meisner ($72.5 million), as well as a same-store increase of $2.40 billion, or 25.6%.

_Gross Profit_—Gross profit increased $719.5 million, or 48.7%, to $2.20 billion in 2025 as compared to 2024.

Additionally, we achieved improvements in project execution at our Texas modular operation ($124.3 million).

| ​ | ​ | ​ | ​ | | ​ | | ​ | | ​ | | ​ | | | |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| ​ | ​ ​ ​ | 2025 | | | | ​ ​ ​ | | 2024 | | | | | | |

| SG&A | ​ | $ | | 883,284 | | ​ | | $ | | 730,072 | | | ​ | |

| Same-store SG&A, excluding amortization expense | ​ | $ | | 799,647 | | ​ | | $ | | 674,703 | | | ​ | |

_Interest Income_—Interest income increased $10.1 million, or 87.0%, in 2025 as compared to 2024.

_Interest Expense_—Interest expense increased $2.4 million, or 35.5%, in 2025 as compared to 2024.

Additionally, we expensed $0.3 million in 2025 related to unamortized debt issuance costs for lenders who exited the credit facility when we amended our senior credit facility in August of 2025.

This decrease was primarily caused by lower earn-out expenses for Summit, driven by larger changes in their forecasted results in the prior year and as a result of them reaching their maximum cumulative earn-out target.

The effective rate for 2025 was slightly lower than the 21% federal statutory rate primarily due to a $30.5 million credit for increasing research activities (“R&D tax credit”) (2.4%) partially offset by $30.3 million of net state income taxes (2.3%).

2025 Compared to 2024

These increases were partially offset by a $778.9 million decrease in accounts payable and other current liabilities driven by the size and timing of payments.

In 2023, we filed our 2022 federal tax return requesting a refund of our $107.1 million overpayment, which was received in April 2025 and positively impacted our second quarter cashflows.

Along with the refund, we received $11.3 million (or $8.9 million, net of tax) of interest income that reduced our provision for income taxes in the first quarter of 2025.

The $126.3 million increase in cash used is primarily due to an increase in share repurchases of $158.1 million and an increase in payments of dividends to stockholders of $26.1 million in the current year.

These increases were partially offset by higher net borrowings of debt in the current year compared to 2024.

On August 27, 2025, we amended our senior credit facility (as amended, the “Facility”) arranged by Wells Fargo Bank, National Association, as administrative agent, and provided by a syndicate of banks, which increases our borrowing capacity from $850.0 million to $1.10 billion.

The line of credit includes a sublimit for up to $200.0 million of letters of credit and a sublimit for up to $75.0 million of swingline loans.

As a result of the amendment, $0.3 million of unamortized costs associated with lenders who exited the Facility were written off to interest expense in the third quarter of 2025.

The remaining $1.0 million of unamortized costs from the previous facility will be deferred and amortized over the term of the new Facility.

In 2025, we incurred approximately $3.7 million in

financing and professional costs in connection with the amendment to the Facility, which, combined with previously unamortized costs of $1.0 million, are being amortized on a straight-line basis as a non-cash charge to interest expense over the remaining term of the Facility.

office, technology, retail and government facilities.

developments in any given sector.

| Under $2 million | | 6,889 | ​ | $ | 1,564.7 | ​ |

| $2 million - $10 million | | 726 | ​ | | 3,236.6 | ​ |

| Total | | 7,935 | ​ | $ | 14,345.0 | ​ |

In 2020, the advent of a global pandemic led to some delays in service and construction, including delayed project starts and air pockets or pauses during 2020 and 2021.

We expect that constraints and delays in our supply chain will continue to abate in the near term; however, we anticipate that pressure on cost and availability, especially for skilled labor, will continue in 2025.

We will continue to invest in our service business, to pursue the more active sectors in our markets, and to emphasize our regional and national account business.

_Revenue_—Revenue increased $1.82 billion, or 35.0%, to $7.03 billion in 2024 compared to 2023.

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

The sequential backlog increase was partially offset by the completion of project work in the technology sector at our Texas electrical operation ($52.6 million).

The year-over-year backlog increase was partially offset by the completion of project work in the manufacturing sector at our North Carolina operations ($68.9 million) and in the manufacturing and technology sectors at one of our Indiana operations ($67.1 million).

_Gross Profit_—Gross profit increased $485.9 million, or 49.1%, to $1.48 billion in 2024 as compared to 2023.

Two of our Texas operations achieved both higher volumes and improvements in project execution ($131.7 million).

Additionally, we achieved increased volumes at one of our Virginia operations ($28.0 million), one of our Tennessee operations ($22.6 million) and our North Carolina operation ($19.8 million).

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| --- | --- | --- | --- | --- | --- | --- | --- |

| | | | | | | | |

| SG&A | ​ | $ | 730,072 | ​ | $ | 574,423 | ​ |

| Same-store SG&A, excluding amortization expense | ​ | $ | 652,752 | ​ | $ | 536,189 | ​ |

_Interest Income_—Interest income increased $8.1 million, or 230.9%, in 2024 as compared to 2023.

_Interest Expense_—Interest expense decreased $3.6 million, or 35.3%, in 2024 as compared to 2023.

This increase was primarily caused by higher expenses at Summit, driven by stronger actual current earnings and forecasted results.

Expense or income from changes in earn-out valuations may be more volatile in future periods due to large earn-out agreements for acquisitions that closed in 2024.

The effective rate for 2023 was lower than the 21% federal statutory rate due to the R&D tax credit (6.3%) and an increase in the R&D tax credit for the 2022 tax year (2.8%).

These R&D tax credit benefits were partially offset by net state income taxes (3.7%) and nondeductible expenses (1.5%).

2023 Compared to 2022

We experienced strong ongoing demand in 2024, although we continue to experience increased labor costs and impacts from supply chain shortages, including delays in delivery of certain materials and equipment.

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| ​ | | 2024 | | | 2023 | | | 2022 | | |

On July 22, 2024, due to Hurricane Beryl, the Internal Revenue Service announced tax relief that extended the due dates for our federal tax payments until February 3, 2025.

These increases were partially offset by a $317.0 million change in billings in excess of costs and deferred revenue due to more advance payments received in the prior year.

We have received large advance payments in the current and prior years that will reverse when project costs are incurred, except to the extent that additional advance payments are received.

The $137.8 million decrease in cash used is primarily due to higher net repayments of debt

in the prior year as operating cash flows were used to pay down outstanding debt, partially offset by increased share repurchases of $36.7 million in the current year.

2023 Compared to 2022

| ​ | | 2024 | | | 2023 | | | 2022 | | |

We are exposed to market risk primarily related to potential adverse changes in interest [removed: rates, as discussed below.][added: rates.]

We are not exposed to any other significant financial market [removed: risks, including commodity price risk,] [added: risks] or foreign currency exchange risk from the use of derivative financial instruments.

The following table presents principal amounts (stated in thousands) and related average interest rates by year of maturity for our debt obligations at December 31, [removed: 2024:][added: 2025:]

| ​ | | Twelve Months Ending December 31, | | | | | | | | | | | | | | | | [added: | | | | | | | | | | | | | | |] ​ | | ​ | [added: |] ​ | | | [added: |] ​ | | [added: |] ​ | ​ | | | [added: | |] ​ | | [added: | | | |]

| ​ | [removed: | 2025] [added: ​ ​ ​] | [added: 2026] | | [removed: 2026] | [added: ​ ​ ​] | | 2027 | | | [added: | | ​ ​ ​ | |] 2028 | | | [added: | | ​ ​ ​ |] 2029 | | | | | [added: ​ ​ ​] | [added: | 2030 | | | | | ​ ​ ​ | |] Thereafter | | | | | | [added: | | ​ ​ ​ | | | |] Total | | | | | | [added: | | | |]

| Average [removed: Interest Rate] [added: interest rate] | ​ | | [removed: 5.0%] [added: 4.8%] | [added: |] ​ | | [removed: 5.3%] | [removed: ​] | [added: 4.8%] | [removed: 5.5%] | [added: |] ​ | | [removed: 5.5%] | [added: 4.7% | | | |] ​ | | 6.0% | | | [added: | |] ​ | | [added: —] | [added: | | | ​ | | | |] — | | | [added: | | | |] ​ | | | [removed: 5.4%] | [added: 4.8%] | | [added: | | | |] ​ | | [added: |]

There were no outstanding borrowings on the revolving credit facility as of December 31, [removed: 2024 and 2023.][added: 2024.]

There is some market risk from fluctuations in the prices of certain commodities and materials due to tariffs or other macroeconomic factors.

In many cases, these increased costs are recoverable, and we do not expect these potential cost increases to have a material impact on our results of operations.

| ​ | | | | ​ | | ​ | | ​ | | ​ | ​ | | ​ | | | ​ | ​ | ​ | | | | ​ | ​ | ​ | | | | | ​ | ​ | ​ | | | | | | | ​ | ​ | ​ | | | | | | ​ | | ​ | ​ | | | | | | ​ |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| Fixed rate debt | ​ | $ | 6,163 | | ​ | | $ | | 24,246 | | | ​ | | $ | 14,272 | | | | ​ | $ | 545 | | | | | ​ | $ | — | | | | ​ | | $ | | — | | | | | | | ​ | | | $ | 45,226 | | | | | | ​ | | |

| Variable rate debt | ​ | $ | — | | ​ | | $ | | — | | | ​ | | $ | — | | | | ​ | $ | — | | | | | ​ | $ | 100,000 | | | | ​ | | $ | | — | | | | | | | ​ | | | $ | 100,000 | | | | | | ​ | | |

The weighted average interest rate applicable to the borrowings under the revolving credit facility was approximately 5.0% as of December 31, 2025.

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | | ​ | | | ​ | ​ | | ​ | | | ​ | | | |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| Fixed Rate Debt | ​ | $ | 6,042 | ​ | $ | 30,697 | ​ | $ | 26,029 | ​ | $ | 5,022 | ​ | $ | 545 | | | ​ | | $ | — | | | ​ | | $ | 68,335 | | | ​ | |

We build, install, maintain, repair and replace mechanical, electrical and plumbing (“MEP”) systems [removed: throughout] [added: through] our [removed: 47] [added: 50] operating units with [removed: 178] [added: 190] locations in [removed: 136] [added: 142] cities throughout the United States.

Substantially all of our consolidated [removed: 2024] [added: 2025] revenue was derived from commercial, industrial and institutional customers and multi-family residential projects.

Approximately [removed: 56.7%] [added: 63.2%] of our revenue was attributable to installation services in newly constructed facilities and [removed: 43.3%] [added: 36.8%] was attributable to renovation, expansion, maintenance, repair and replacement services in existing buildings.

Our consolidated [removed: 2024] [added: 2025] revenue was derived from the following service industries:

| ​ | [added: ​ ​ ​] | Percentage of | |

| Mechanical Services | | [removed: 78.7] [added: 73.3] | % |

| Electrical Services | ​ | [removed: 21.3] [added: 26.7] | % |

We believe that commercial, industrial, and institutional mechanical and electrical contracting generate annual revenue in the United States of approximately [removed: $550] [added: $700] billion.

Older commercial, industrial and institutional facilities frequently have poor air quality and provide less comfortable environments, and older HVAC systems result in significantly higher energy consumption than [removed: do] modern systems.

| | ● | construction of and installation in new buildings, which provided approximately [removed: 56.7%] [added: 63.2%] of our revenue in [removed: 2024,] [added: 2025,] and |

| | ● | renovation, expansion, maintenance, repair and replacement in existing buildings, which provided the remaining [removed: 43.3%] [added: 36.8%] of our [removed: 2024] [added: 2025] revenue. |

In “design and build” projects, the commercial MEP company is responsible for designing, engineering and installing a cost-effective, energy-efficient [removed: system customized to the specific needs of the building owner.]

Costs and other project terms are normally negotiated [added: between the building owner or its representative and the contracting company.]

We believe that the work we perform to [removed: optimize] [added: enhance] and upgrade systems and controls helps Comfort Systems [removed: USA] to optimize energy use and fundamentally reduce our nation’s carbon footprint.

Our distribution of revenue in [removed: 2024] [added: 2025] by end-use sector was as follows:

| Office Buildings | | [removed: 6.0] [added: 5.0] | % |

| Retail, Restaurants and Entertainment | | [removed: 5.4] [added: 3.7] | % |

| Multi-Family and Residential | | [removed: 2.0] [added: 1.4] | % |

Approximately [removed: 91.1%] [added: 92.7%] of our revenue is earned on a project basis for installation of systems in newly constructed or existing facilities.

As of December 31, [removed: 2024,] [added: 2025,] we had [removed: 7,935] [added: 8,427] projects in process with an aggregate contract value of approximately [removed: $14.35] [added: $24.17] billion.

Our average project takes six to nine months to complete, with an average contract price of approximately [removed: $1.8] [added: $2.9] million.

This average project size, when taken together with the approximately [removed: 8.9%] [added: 7.3%] of our revenue derived from maintenance and service, provides us with a broad base of work in the construction services sector.

_Excel at Modular and Off-Site Construction_—We believe that modular and off-site construction – the ability to build superior quality plants and systems away from the construction site – [removed: will] [added: has] become increasingly important in complex construction projects.

We are actively concentrating managerial and sales resources on training and hiring experienced employees to sell and [added: profitably perform service work.]

_Construction and Installation Services for New Buildings_—Our installation business related to newly constructed facilities, which comprised approximately [removed: 56.7%] [added: 63.2%] of our consolidated [removed: 2024] [added: 2025] revenue, involves the design, engineering, integration, installation and start-up of MEP and related systems.

Our average project takes six to nine months to complete, with an average contract price of approximately [removed: $1.8] [added: $2.9] million.

We also perform larger project work, with [removed: 1,046] [added: 1,668] contracts in progress [removed: at] [added: as of] December 31, [removed: 2024] [added: 2025] with contract prices in excess of $2 million.

Our largest project in progress [removed: at] [added: as of] December 31, [removed: 2024] [added: 2025] had a contract price of [removed: $168.9] [added: $496.9] million.

_Renovation, Expansion, Maintenance, Monitoring, Repair and Replacement Services for Existing Buildings_—Our renovation, expansion, maintenance, monitoring, repair and replacement services in existing buildings comprised approximately [removed: 43.3%] [added: 36.8%] of our consolidated [removed: 2024] [added: 2025] revenue.

Commercial, industrial and institutional service agreements usually have terms of one or more years, with automatic annual renewals, and frequently include [removed: thirty-] [added: 30-] to [removed: sixty-day] [added: 60-day] cancellation notice periods.

Accordingly, we expect our revenue and operating results [removed: generally] will [added: generally] be lower in the first calendar quarter.

We have a diverse customer base, with our top customer representing [removed: 13.3%] [added: 12.8%] of consolidated [removed: 2024] [added: 2025] revenue.

_Employees_—As of December 31, [removed: 2024,] [added: 2025,] we had approximately [removed: 18,300] [added: 22,700] employees as compared to approximately [removed: 15,800] [added: 18,300] employees as of December 31, [removed: 2023.][added: 2024.]

We have collective bargaining agreements covering [removed: 50] [added: 9] employees.

These values set the foundation for our Code of Conduct, which applies to all employees, officers, and directors of the Comfort Systems [removed: USA] family of companies.

_Safety_—We have established comprehensive safety programs throughout our operations to ensure that [removed: all] [added: our] employees comply with safety standards we have established and that are established under federal, state, and local laws and regulations.

Our rate of incidents recordable under the standards of the Occupational Safety and Health Administration (“OSHA”) per one hundred employees per year, also known as the OSHA recordable rate, was [removed: 0.97] [added: 0.93] during [removed: 2024.][added: 2025.]

We [removed: know] [added: believe] that diversity is [removed: truly] a competitive advantage that [added: strengthens our workforce and] helps drive growth and innovation.

Our Board of Directors [added: (the “Board”)] and Board committees provide oversight on certain human capital matters, including our diversity and inclusion strategy.

We generally warrant labor for [removed: thirty] [added: 30] days after servicing existing MEP systems.

system customized to the specific needs of the building owner.

| Technology | ​ | 45.0 | % |

| Manufacturing | ​ ​ ​ | 22.1 | % |

| Healthcare | | 8.9 | % |

| Education | | 7.3 | % |

| Government | | 5.0 | % |

| Other | | 1.6 | % |

and access to bonding, (v) range of capabilities, and (vi) scale of operation.

We seek to

between the building owner or its representative and the contracting company.

We believe that we have realized scale benefits from coordinated purchasing, technical innovation, insurance, benefits, bonding, and financing activities across our operations.

| Technology | ​ | 33.2 | % |

| Manufacturing | | 27.3 | % |

| Education | | 10.0 | % |

| Healthcare | | 8.3 | % |

| Government | | 5.4 | % |

| Other | | 2.4 | % |

profitably perform service work.

To improve our competitive position, we

As of December 31, [removed: 2024,] [added: 2025,] we recorded an accrual for unresolved matters, which is not material to our financial statements, based on our analysis of likely outcomes related to the respective matters; however, it is possible that the ultimate outcome and associated costs will deviate from our estimates and that, in the event of an unexpectedly adverse outcome, we may experience additional costs and expenses in future periods.

In 2022, we recorded a net gain of $5.1 million related to legal matters that merited changes to our assessments of the related accruals in the ordinary course of our business based on information received in 2022.

The largest change resulted from favorable developments related to a dispute with a customer regarding the outcome of a completed project as well as the obligation to perform subcontract work under two executed letters of intent for subsequent projects that we believed were not enforceable.

The net gain of $5.1 million was recorded primarily as an increase in gross profit in our Consolidated Statements of Operations.

| For the fiscal year ended December 31, [removed: 2024] [added: 2025] | |

Houston, Texas [removed: 77057][added: 77024]

| Title of Each Class | [removed: Trading] [added: ​Trading] Symbol(s) | Name of Each Exchange on which Registered |

The aggregate market value of the voting stock held by non-affiliates of the registrant at June 30, [removed: 2024] [added: 2025] was approximately [removed: $10.67] [added: $18.64] billion, based on the [removed: $304.12] [added: $536.21] last sale price of the registrant’s common stock on the New York Stock Exchange on June 30, [removed: 2024.][added: 2025.]

As of February [removed: 14, 2025, 35,553,062] [added: 13, 2026, 35,174,967] shares of the registrant’s common stock were outstanding (excluding treasury shares of [removed: 5,570,303).][added: 5,948,398).]

The information required by Part III (other than the required information regarding executive officers) is incorporated by reference from the registrant’s definitive proxy statement, which will be filed with the Commission not later than 120 days following December 31, [removed: 2024.][added: 2025.]

| [Item [removed: 1C.](#ITEM1CCybersecurity)] [added: 1C.](#Cybersecurity)] | [removed: [Cybersecurity](#ITEM1CCybersecurity)] [added: [Cybersecurity](#Cybersecurity)] | 23 |

| [Item 6.](#ITEM6SelectedFinancialData_853719) | [Reserved](#ITEM6SelectedFinancialData_853719) | [removed: 28] [added: 27] |

| [Item 7.](#ITEM7ManagementsDiscussionandAnalysisofF) | [Management’s Discussion and Analysis of Financial Condition and Results of Operations](#ITEM7ManagementsDiscussionandAnalysisofF) | [removed: 28] [added: 27] |

| [Item 7A.](#ITEM7AQuantitativeandQualitativeDisclosu) | [Quantitative and Qualitative Disclosures about Market Risk](#ITEM7AQuantitativeandQualitativeDisclosu) | [removed: 40] [added: 39] |

| [Item 9.](#ITEM9ChangesinandDisagreementswithAccoun) | [Changes in and Disagreements with Accountants on Accounting and Financial Disclosure](#ITEM9ChangesinandDisagreementswithAccoun) | [removed: 77] [added: 75] |

| [Item 9A.](#ITEM9AControlsandProcedures_403685) | [Controls and Procedures](#ITEM9AControlsandProcedures_403685) | [removed: 77] [added: 75] |

| [Item 9B.](#ITEM9BOtherInformation_701400) | [Other Information](#ITEM9BOtherInformation_701400) | [removed: 79] [added: 77] |

| [Item 9C.](#ITEM9CDisclosureRegardingForeignJurisdic) | [Disclosure Regarding Foreign Jurisdictions that Prevent Inspections](#ITEM9CDisclosureRegardingForeignJurisdic) | [removed: 79] [added: 77] |

| [Item 10.](#ITEM10DirectorsExecutiveOfficersandCorpo) | [Directors, Executive Officers and Corporate Governance](#ITEM10DirectorsExecutiveOfficersandCorpo) | [removed: 79] [added: 77] |

| [Item 11.](#ITEMS111213AND14_316091) | [Executive Compensation](#ITEMS111213AND14_316091) | [removed: 79] [added: 77] |

| [Item 12.](#ITEMS111213AND14_316091) | [Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters](#ITEMS111213AND14_316091) | [removed: 79] [added: 77] |

| [Item 13.](#ITEMS111213AND14_316091) | [Certain Relationships and Related Transactions, and Director Independence](#ITEMS111213AND14_316091) | [removed: 79] [added: 77] |

| [Item 14.](#ITEMS111213AND14_316091) | [Principal Accounting Fees and Services](#ITEMS111213AND14_316091) | [removed: 79] [added: 77] |

| [Item 15.](#ITEM15ExhibitsandFinancialStatementSched) | [Exhibits and Financial Statement Schedules](#ITEM15ExhibitsandFinancialStatementSched) | [removed: 79] [added: 77] |

| [Item 16.](#ITEM16Form10KSummary) | [Form 10-K Summary](#ITEM16Form10KSummary) | [removed: 80] [added: 78] |

_Certain statements and information in this Annual Report on Form 10-K may constitute [removed: forward looking] [added: forward-looking] statements [removed: within the meaning of] [added: regarding our future business expectations, which are subject to] applicable securities laws and regulations.

The words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” or other similar expressions are intended to identify [removed: forward looking] [added: forward-looking] statements, which are generally not historic in nature.

These forward-looking statements are based on the current expectations and beliefs of [removed: Comfort Systems USA, Inc. and its subsidiaries (collectively,] the [removed: “Company”)] [added: Company] concerning future developments and their effect on the Company.

While the Company’s management believes that these [removed: forward looking] [added: forward-looking] statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates, and the Company’s actual results of operations, financial condition and liquidity, and the development of the industry in which the Company operates, may differ materially from those made in or suggested by the forward-looking statements contained in this Annual Report on Form 10-K.

The Company undertakes no obligation to publicly update or revise any forward-looking statements after the date they are made, whether [removed: as a result] [added: because] of new information, future events, or [removed: otherwise.][added: otherwise, except as otherwise required by law.]

The terms “Comfort Systems,” “we,” “us,” [added: “our,”] or “the Company” refer to Comfort Systems USA, Inc. or Comfort Systems USA, Inc. and its consolidated subsidiaries, as appropriate in the context.

9753 Katy Freeway

Suite 700

Important factors that could cause actual results to differ materially from those in the forward-looking statements include, but are not limited to: the use of incorrect estimates for bidding a fixed-price contract; undertaking contractual commitments that exceed the Company’s labor resources; failing to perform contractual obligations efficiently enough to maintain profitability; national or regional weakness in construction activity and economic conditions; economic downturns in the markets where the Company operates; shortages of labor and specialty building materials or material increases to the cost thereof; financial difficulties affecting projects, vendors, customers, or subcontractors; unexpected adjustments or cancellations in our backlog resulting in the Company’s backlog failing to translate into actual revenue or profits; inflation, supply chain disruptions, and capital market volatility; the loss of significant customers; intense competition in the Company’s industry; risks associated with acquisitions, including the ability to successfully integrate those companies; impairment charges for goodwill and intangible assets; reductions or reversals of previously recorded revenue or profits as a result of the Company’s cost-to-cost input method of accounting; difficulties in the financial and surety markets; delays and/or defaults in customer payments; difficult work environment; worldwide political and economic uncertainties, including international conflicts and epidemics or pandemics; attraction and retention of key management and employees; the Company’s decentralized management structure; our ability to effectively manage our backlog and the size and cost of our operations; failure of third party subcontractors and suppliers to complete work as anticipated; difficulty in obtaining, or increased costs associated with, bonding and insurance; our ability to remain in compliance with covenants under our credit agreement, service our indebtedness, or fund our other liquidity needs; our inability to properly utilize our workforce; increases and uncertainty in insurance costs; regulatory and legal risks, including adverse litigation results, failure to comply with laws and regulations; changes in United States trade policy, and tax-related risks; the imposition of past and future liability from environmental, safety, and health regulations including the inherent risk associated with self-insurance; an increase in our effective tax rate; a material information technology failure or a material cybersecurity breach; risks related to our common stock; failure or circumvention of our disclosure controls and procedures or internal control environment; our ability to manage growth and geographically-dispersed operations; severe weather conditions (such as storms, droughts, extreme heat or cold, wildfires and floods), including as a result of climate change, and any resulting regulations or restrictions related thereto; force majeure events; deliberate, malicious acts, including terrorism and sabotage; findings of inadequate internal controls; changes in accounting rules and regulations; and other risks detailed in our reports filed with the Securities and Exchange Commission (the “SEC”)._

*​*

_For additional information regarding known material factors that could cause the Company’s results to differ from its projected results, please see its filings with the SEC, including its Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K._

*​*

675 Bering Drive

Suite 400

Known material factors that could cause the Company’s actual results to differ from those in the forward-looking statements are those described in Part I, “Item 1A.

Risk Factors.”_

The Company has adopted processes designed to identify, assess and manage material risks from cybersecurity threats, and the Company’s full Board and management [removed: is] [added: are] actively involved in overseeing the risk management process.

As of December 31, [removed: 2024,] [added: 2025,] we owned [removed: 20] [added: 25] properties.

Generally, leases range from [removed: three] [added: 3] to [removed: ten] [added: 15] years and are on terms we believe to be commercially reasonable.

To maximize available capital, we generally intend to continue to lease our [removed: properties,] [added: properties] but may consider further purchases of property where we believe ownership would be more economical.

Lane,_ age [removed: 67,] [added: 68,] has served as [removed: our] Chief Executive Officer [removed: and President] since December 2011 and as a [removed: director] [added: Director] since November 2010.

Mr. Lane served as [removed: our] President [added: from December 2011 to December 2025] and [added: as President and] Chief Operating Officer from March 2010 until December 2011.

Mr. Lane’s additional experience [removed: includes] [added: included] serving as a Regional Director of Capstone Turbine Corporation, a distributed power manufacturer.

Mr. Lane [removed: holds] [added: earned] a Bachelor of Science in Chemistry from the University of Notre Dame and [removed: a Master of Business Administration] [added: his MBA] from Boston College.

_William George,_ age [removed: 60,] [added: 61,] has served as our Executive Vice President and Chief Financial Officer since May 2005, was our Senior Vice President, General Counsel and Secretary from May 1998 to May 2005, and was our Vice President, General Counsel and Secretary from March 1997 to April 1998.

McKenna,_ age [removed: 52,] [added: 53,] has served as [removed: Executive Vice] President and Chief Operating Officer since January [removed: 2022 and was formerly Senior Vice President and Chief Operating Officer during 2021.][added: 2026.]

[removed: From] [added: Prior to joining the Company, from] February 1999 to August 2004, Mr. McKenna was a practicing attorney in the area of complex commercial litigation in the Houston, Texas, office of Akin Gump Strauss Hauer & Feld LLP, an international law firm.

Shaeff,_ age [removed: 59,] [added: 60,] has served as our Senior Vice President and Chief Accounting Officer since May 2005, was our Vice President and Corporate Controller from March 2002 to May 2005, and was our Assistant Corporate Controller from September 1999 to February 2002.

[removed: Howell,_] [added: Eslicker,_] age [removed: 37,] [added: 35,] has served as Senior Vice President and General Counsel for the Company since [removed: January 2022 and formerly served as Vice President and General Counsel from January 2019 to] December [removed: 2021.][added: 2025.]

_Terrence Reed_, age [removed: 65,] [added: 66,] has served as Senior Vice President, Chief Human Resources Officer since January 2024 and formerly served as Senior Vice President of People and Leadership Development from March 2021 to [removed: December 2023.]

Mr. Lane is a member of the Board of Directors of Main Street Capital Corporation and previously served as a member of the Board of Directors of Griffin Dewatering Corporation.

Prior to his current position, Mr. McKenna served as Chief Operating Officer for the Company from January 2022 to December 2025.

Mr. McKenna also served in various roles at the Company since 2004, including Senior Vice President, Vice President – Region 4, General Counsel and Secretary.

_Rachel R.

Prior to her current position, Ms. Eslicker served as Associate General Counsel and Assistant Corporate Secretary from January 2023 to December 2025 and as Senior Corporate Counsel from January 2019 to December 2022.

Ms. Eslicker started her career as an associate in the Mergers and Acquisitions and Capital Markets department of the Houston, Texas, office of Vinson & Elkins LLP.

Ms. Eslicker holds Bachelor of Arts degrees in Government and History from the University of Texas and a Juris Doctorate from Duke University School of Law.

December 2023.

Mr. McKenna previously served as our Senior Vice President and Vice President – Region 4 from January 2019 to December 2020; Senior Vice President, General Counsel and Secretary from August 2013 to December 2018; Vice President, General Counsel and Secretary from May 2005 to August 2013; and Associate General Counsel from August 2004 to May 2005.

_Laura F.

Previously, Ms. Howell served as the Associate General Counsel from January 2018 to December 2018 and as Senior Counsel, Corporate from November 2014 to December 2017.

Prior to joining the Company, she was an associate in the

corporate department of the Houston office of Latham & Watkins, LLP from November 2013 to October 2014.

From September 2012 to October 2013, Ms. Howell was an associate in the corporate department of the Silicon Valley office of Fenwick & West, LLP.

Ms. Howell holds a Bachelor of Arts in Economics from Wake Forest University and a Juris Doctorate from Stanford Law School.

As of February [removed: 14, 2025,] [added: 13, 2026,] there were approximately [removed: 231] [added: 211] stockholders of record of our Common Stock, and the last reported sale price on that date was [removed: $391.22] [added: $1,337.95] per share.

[removed: ][added: ]

On March 29, 2007, our Board [removed: of Directors (the “Board”)] approved a stock repurchase program to acquire up to 1.0 million shares of our outstanding common stock.

On [removed: August 7, 2024,] [added: May 16, 2025,] the Board approved an extension to the program by increasing the shares authorized for repurchase by 0.4 million shares.

Since the inception of the repurchase program, the Board has approved [removed: 11.4] [added: 11.8] million shares to be repurchased.

As of December 31, [removed: 2024,] [added: 2025,] we have repurchased a cumulative total of [removed: 10.4] [added: 10.9] million shares at an average price of [removed: $31.41] [added: $50.15] per share under the repurchase program.

The share repurchases will be made from time to time at our discretion in the open market or privately negotiated transactions, [added: including pursuant to Rule 10b5-1 share repurchase plans,] as permitted by securities laws and other legal requirements, and subject to market conditions and other factors.

During the year ended December 31, [removed: 2024,] [added: 2025,] we repurchased [removed: 0.2] [added: 0.4] million shares for approximately [removed: $58.3 million] [added: $217.9 million, inclusive of the applicable excise tax,] at an average price of [removed: $329.14] [added: $489.40] per share.

During the year ended December 31, [removed: 2024,] [added: 2025,] we purchased our common shares in the following amounts at the following average prices:

| ​ | [added: ​ ​ ​] | ​ | [added: ​ ​ ​] | ​ | ​ | [added: ​ ​ ​] | Total Number of Shares | [added: ​ ​ ​] | Maximum Number of | |

| | (1) | Purchased as part of a [added: stock repurchase] program announced on March 29, 2007 under which, since the inception of this program, [removed: 11.4] [added: 11.8] million shares have been approved for repurchase. |

| January 1 - January 31 | | 3,000 | ​ | $ | 426.13 | | 10,436,482 | | 919,069 | ​ |

| February 1 - February 28 | | 63,450 | ​ | $ | 378.18 | | 10,499,932 | | 855,619 | ​ |

| March 1 - March 31 | | 197,604 | ​ | $ | 338.91 | | 10,697,536 | | 658,015 | ​ |

| April 1 - April 30 | | 56,909 | ​ | $ | 309.22 | | 10,754,445 | | 601,106 | ​ |

| May 1 - May 31 | | 4,619 | ​ | $ | 429.21 | | 10,759,064 | | 998,900 | ​ |

| June 1 - June 30 | | 850 | ​ | $ | 472.27 | | 10,759,914 | | 998,050 | ​ |

| July 1 - July 31 | | — | ​ | $ | — | | 10,759,914 | | 998,050 | ​ |

| August 1 - August 31 | | 5,080 | ​ | $ | 684.30 | | 10,764,994 | | 992,970 | ​ |

| September 1 - September 30 | | 13,875 | ​ | $ | 701.04 | | 10,778,869 | | 979,095 | ​ |

| October 1 - October 31 | | — | ​ | $ | — | | 10,778,869 | | 979,095 | ​ |

| November 1 - November 30 | | 74,010 | ​ | $ | 923.67 | | 10,852,879 | | 905,085 | ​ |

| December 1 - December 31 | | 25,775 | ​ | $ | 934.21 | | 10,878,654 | | 879,310 | ​ |

| ​ | | 445,172 | ​ | $ | 489.40 | | 10,878,654 | | 879,310 | ​ |

As of December 31, 2024, the Company is no longer included in the Russell 2000 Index.

Given that construction-specific indexes include engineering firms, general contractors, and other organizations that derive a majority of their revenue from providing professional services, we do not believe there is an industry specific index that serves as an accurate comparison to our performance.

While not directly comparable, the Company believes that the S&P 400 Capital Good Index is an appropriate trade or line of business index given that the Company is included within the index and the index includes not only construction and engineering companies, but also companies that manufacture and install building products and electrical equipment.

We intend to use the S&P 400 Capital Goods Index, rather than the Russell 2000 Index, for the purpose of Item 201(e) of Regulation S-K going forward.

In accordance with Item 201(e) of Regulation S-K, the stock performance graph above includes the Russell 2000 Index and the S&P 400 Capital Goods Index.

​

| January 1 - January 31 | | 1,500 | ​ | $ | 196.89 | | 10,257,824 | | 686,301 | ​ |

| February 1 - February 29 | | — | ​ | $ | — | | 10,257,824 | | 686,301 | ​ |

| March 1 - March 31 | | — | ​ | $ | — | | 10,257,824 | | 686,301 | ​ |

| April 1 - April 30 | | — | ​ | $ | — | | 10,257,824 | | 686,301 | ​ |

| May 1 - May 31 | | 13,650 | ​ | $ | 307.97 | | 10,271,474 | | 672,651 | ​ |

| June 1 - June 30 | | 21,347 | ​ | $ | 311.09 | | 10,292,821 | | 651,304 | ​ |

| July 1 - July 31 | | 32,219 | ​ | $ | 305.13 | | 10,325,040 | | 619,085 | ​ |

| August 1 - August 31 | | 44,192 | ​ | $ | 315.12 | | 10,369,232 | | 986,319 | ​ |

| September 1 - September 30 | | 23,550 | ​ | $ | 314.55 | | 10,392,782 | | 962,769 | ​ |

| October 1 - October 31 | | 17,250 | ​ | $ | 388.27 | | 10,410,032 | | 945,519 | ​ |

| November 1 - November 30 | | 22,400 | ​ | $ | 395.39 | | 10,432,432 | | 923,119 | ​ |

| December 1 - December 31 | | 1,050 | ​ | $ | 428.70 | | 10,433,482 | | 922,069 | ​ |

| ​ | | 177,158 | ​ | $ | 329.14 | | 10,433,482 | | 922,069 | ​ |

| ​ | [added: ​ ​ ​] | Page |

| [removed: [Comfort] [added: Comfort] Systems USA, [removed: Inc.](#COMFORTSYSTEMSUSAINC_496109)] [added: Inc.] | ​ | ​ |

We have audited the accompanying consolidated balance sheets of Comfort Systems USA, Inc. and subsidiaries (the “Company”) as of December 31, [removed: 2024] [added: 2025] and [removed: 2023,] [added: 2024,] the related consolidated statements of operations, stockholders’ equity, and cash flows, for each of the three years in the period ended December 31, [removed: 2024,] [added: 2025,] and the related notes (collectively, referred to as the “financial statements”).

In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, [removed: 2024] [added: 2025] and [removed: 2023,] [added: 2024,] and the results of its operations and its cash flows for each of the three years in the period ended December 31, [removed: 2024,] [added: 2025,] in conformity with accounting principles generally accepted in the United States of America.

We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company’s internal control over financial reporting as of December 31, [removed: 2024,] [added: 2025,] based on criteria established in _Internal Control — Integrated Framework (2013)_ issued by the Committee of Sponsoring Organizations of the Treadway Commission and our report dated February [removed: 20, 2025,] [added: 19, 2026,] expressed an unqualified opinion on the Company’s internal control over financial reporting.

The critical audit matter communicated below is a matter arising from the current-period audit of the [removed: consolidated] financial statements that was communicated or required to be communicated to the audit committee and that (1) relates to accounts or disclosures that are material to the [removed: consolidated] financial statements and (2) involved our especially challenging, subjective, or complex judgments.

The communication of [removed: this] critical audit [removed: matter] [added: matters] does not alter in any way our opinion on the [removed: consolidated] financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

[removed: Such revisions are] frequently based on further estimates and subjective assessments.

| ​ | [added: ​ ​ ​] | [added: | 2025 | | ​ ​ ​ |] 2024 | | [added: ​ ​ ​] | 2023 | | [removed: ​] |

| [removed: Cash and cash equivalents] [added: CASH AND CASH EQUIVALENTS, beginning of period] | ​ | [removed: $] | 549,939 | ​ | [removed: $] | 205,150 | ​ | [added: | 57,214 | ​ |]

| Billed accounts receivable, less allowance for credit losses of [removed: $15,286] [added: $19,708] and [removed: $11,926,] [added: $15,286,] respectively | ​ | | [removed: 1,861,212] [added: 2,577,858] | ​ | | [removed: 1,318,926] [added: 1,861,212] | ​ |

| Unbilled accounts receivable, less allowance for credit losses of [removed: $1,475] [added: $1,508] and [removed: $850,] [added: $1,475,] respectively | ​ | | [removed: 95,786] [added: 123,197] | ​ | | [removed: 72,774] [added: 95,786] | ​ |

| Other receivables, less allowance for credit losses of [removed: $553] [added: $325] and [removed: $522,] [added: $553,] respectively | ​ | | [removed: 86,186] [added: 116,157] | ​ | | [removed: 166,319] [added: 86,186] | ​ |

| Inventories | ​ | | [removed: 59,224] [added: 84,066] | ​ | | [removed: 65,538] [added: 59,224] | ​ |

| Prepaid expenses and other | ​ | | [removed: 46,213] [added: 138,560] | ​ | | [removed: 54,309] [added: 46,213] | ​ |

| Costs and estimated earnings in excess of billings, less allowance for credit losses of [removed: $271] [added: $255] and [removed: $79,] [added: $271,] respectively | ​ | | [removed: 91,681] [added: 88,817] | ​ | | [removed: 28,084] [added: 91,681] | ​ |

| Total current assets | ​ | | [removed: 2,790,241] [added: 4,110,553] | ​ | | [removed: 1,911,100] [added: 2,790,241] | ​ |

| PROPERTY AND EQUIPMENT, NET | ​ | | [removed: 277,180] [added: 387,952] | ​ | | [removed: 208,568] [added: 277,180] | ​ |

| LEASE RIGHT-OF-USE [removed: ASSET] [added: ASSETS] | ​ | ​ | [removed: 229,106] [added: 322,922] | ​ | ​ | [removed: 205,712] [added: 229,106] | ​ |

| GOODWILL | ​ | | [removed: 875,270] [added: 1,025,515] | ​ | | [removed: 666,834] [added: 875,270] | ​ |

| IDENTIFIABLE INTANGIBLE ASSETS, NET | ​ | | [removed: 434,417] [added: 485,168] | ​ | | [removed: 280,397] [added: 434,417] | ​ |

| DEFERRED TAX ASSETS | ​ | ​ | [removed: 85,441] [added: 84,139] | ​ | ​ | [removed: 17,723] [added: 85,441] | ​ |

| OTHER NONCURRENT ASSETS | ​ | | [removed: 19,433] [added: 24,920] | ​ | | [removed: 15,245] [added: 19,433] | ​ |

| Total assets | ​ | $ | [removed: 4,711,088] [added: 6,441,169] | ​ | $ | [removed: 3,305,579] [added: 4,711,088] | ​ |

| Current maturities of long-term debt | ​ | $ | [removed: 6,042] [added: 6,163] | ​ | $ | [removed: 4,867] [added: 6,042] | ​ |

| Accounts payable | ​ | | [removed: 654,943] [added: 696,348] | ​ | | [removed: 419,962] [added: 654,943] | ​ |

| Accrued compensation and benefits | ​ | | [removed: 228,622] [added: 291,722] | ​ | | [removed: 169,136] [added: 228,622] | ​ |

| Billings in excess of costs and estimated earnings and deferred revenue | ​ | | [removed: 1,149,257] [added: 2,120,262] | ​ | | [removed: 909,538] [added: 1,149,257] | ​ |

| Accrued self-insurance | ​ | | [removed: 42,315] [added: 42,973] | ​ | | [removed: 27,774] [added: 42,315] | ​ |

| Other current liabilities | ​ | | [removed: 501,591] [added: 236,382] | ​ | | [removed: 189,928] [added: 501,591] | ​ |

| Total current liabilities | ​ | | [removed: 2,582,770] [added: 3,393,850] | ​ | | [removed: 1,721,205] [added: 2,582,770] | ​ |

| LONG-TERM DEBT | ​ | | [removed: 62,293] [added: 139,063] | ​ | | [removed: 39,345] [added: 62,293] | ​ |

| LEASE LIABILITIES | ​ | | [removed: 212,107] [added: 302,590] | ​ | | [removed: 188,136] [added: 212,107] | ​ |

| DEFERRED TAX LIABILITIES | ​ | | [removed: 2,225] [added: 3,892] | ​ | | [removed: 1,120] [added: 2,225] | ​ |

| OTHER LONG-TERM LIABILITIES | ​ | | [removed: 147,017] [added: 153,000] | ​ | | [removed: 77,944] [added: 147,017] | ​ |

| Total liabilities | ​ | | [removed: 3,006,412] [added: 3,992,395] | ​ | | [removed: 2,027,750] [added: 3,006,412] | ​ |

| Treasury stock, at cost, [removed: 5,562,453] [added: 5,946,145] and [removed: 5,438,625] [added: 5,562,453] shares, respectively | ​ | | [removed: (273,799)] [added: (496,006)] | ​ | | [removed: (209,807)] [added: (273,799)] | ​ |

| Additional paid-in capital | ​ | | [removed: 350,734] [added: 363,314] | ​ | | [removed: 339,562] [added: 350,734] | ​ |

| Retained earnings | ​ | | [removed: 1,627,330] [added: 2,581,055] | ​ | | [removed: 1,147,663] [added: 1,627,330] | ​ |

| Total stockholders’ equity | ​ | | [removed: 1,704,676] [added: 2,448,774] | ​ | | [removed: 1,277,829] [added: 1,704,676] | ​ |

Such revisions are

February 19, 2026

| ​ | | 2025 | | ​ ​ ​ | 2024 | | ​ |

| Net income | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,022,558 | ​ | ​ | 1,022,558 | ​ |

| Issuance of restricted stock & performance stock | ​ | — | ​ | ​ | — | ​ | 63,815 | ​ | ​ | 4,280 | ​ | ​ | 2,321 | ​ | ​ | — | ​ | ​ | 6,601 | ​ |

| Share repurchase | ​ | — | ​ | ​ | — | ​ | (445,172) | ​ | ​ | (217,866) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (217,866) | ​ |

| BALANCE AT DECEMBER 31, 2025 | ​ | 41,123,365 | ​ | $ | 411 | ​ | (5,946,145) | ​ | $ | (496,006) | ​ | $ | 363,314 | ​ | $ | 2,581,055 | ​ | $ | 2,448,774 | ​ |

| Proceeds from investments | ​ | ​ | 27,747 | ​ | ​ | — | ​ | ​ | — | ​ |

| Income taxes, net of refunds | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| Federal | ​ | $ | 204,077 | ​ | $ | 73,000 | ​ | $ | 83,000 |

| State | ​ | ​ | | ​ | ​ | ​ | ​ | ​ | ​ |

| Arizona | ​ | ​ | * | ​ | ​ | 5,536 | ​ | ​ | * |

| Remaining states | ​ | ​ | 49,472 | ​ | ​ | 24,283 | ​ | ​ | 17,254 |

| Subtotal | ​ | ​ | 49,472 | ​ | ​ | 29,819 | ​ | ​ | 17,254 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| * Jurisdiction below the threshold for the period presented. | | | | | | | | | |

Entities may apply the standard prospectively or may elect retrospective application.

estimate an allowance for credit losses.

As of December 31, 2025, we had a $34.4 million investment in U.S. Treasury bills with maturities greater than ninety days but less than one year, which are recorded at amortized cost and is included in “Prepaid Expenses and Other” in our Consolidated Balance Sheet.

over the life of the contract using a cost-to-cost input method to measure progress towards contract completion.

This evaluation requires significant judgment and the

Contract assets decreased from December 31, 2024 to December 31, 2025 by approximately $2.9 million.

The decrease in contract assets included a decrease of $7.5 million attributable to the timing of billings, partially offset by an increase of $4.6 million related to our 2025 acquisitions.

Additionally, there was an increase of $60.9 million as a result of our 2025 acquisitions.

We have adopted the practical expedient that allows us to not include service maintenance contracts with a

| U.S. Treasury bills | ​ | $ | — | ​ | $ | 34,357 | ​ | $ | — | ​ | $ | 34,357 |

Cash equivalents described in (ii) and (iii) above have original maturities of three months or less.

We own U.S. Treasury bills with maturities greater than ninety days but less than one year, which we classify as held-to-maturity in accordance with ASC 320 “Investments – Debt Securities,” given that the Company has the ability and intent to hold the investments until maturity.

These investments are included within “Prepaid Expenses and Other” in the Consolidated Balance Sheet.

Due to the short-term maturity, the amortized cost of our U.S. Treasury bills approximates their fair value.

a significantly higher or lower potential liability.

On October 1, 2025, we acquired all of the issued and outstanding membership interests of Feyen-Zylstra Holdings, LLC (“Feyen Zylstra”), headquartered in Michigan, for a total preliminary purchase price of $109.8 million, which included $99.0 million of cash paid on the closing date, $4.3 million in notes payable to the former owners, an earn-out that will be paid if certain financial targets are met after the acquisition date and a working capital adjustment.

Feyen Zylstra operates in the Midwest and Southern United States and provides electrical design, installation, and maintenance services primarily to the industrial, technology and healthcare sectors.

As a result of the acquisition, Feyen Zylstra is a wholly owned subsidiary of the Company reported in our electrical segment.

The goodwill recognized as a result of the Feyen Zylstra acquisition is deductible for tax purposes.

On October 1, 2025, we acquired all of the issued and outstanding shares of capital stock of Meisner Electric, Inc. (“Meisner”), headquartered in Florida, for a total preliminary purchase price of $74.9 million, which included $64.5 million of cash paid on the closing date, $5.0 million in notes payable to the former owners and a working capital adjustment.

Meisner operates in Florida and provides greenfield construction services and electrical design, installation, and renovation services primarily to the healthcare, commercial and government sectors.

On May 31, 2025, we acquired all of the issued and outstanding shares of capital stock of a mechanical service provider in New York for a total preliminary purchase price of $2.8 million, which is reported in our mechanical segment.

On May 1, 2025, we acquired all of the issued and outstanding membership interests of Right Way Plumbing & Mechanical LLC (“Right Way”), headquartered in Florida, for a total preliminary purchase price of $64.9 million, which included $49.5 million of cash paid on the closing date, $5.0 million in notes payable to the former owners, an earn-out that will be paid if certain financial targets are met after the acquisition date and a working capital adjustment.

Right Way operates in Florida and provides plumbing installation and maintenance services.

| --- | --- | --- |

| --- | --- | --- |

| --- | --- | --- |

February 20, 2025

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| --- | --- | --- | --- | --- | --- | --- | --- |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| BALANCE AT DECEMBER 31, 2021 | | 41,123,365 | ​ | $ | 411 | | (5,032,311) | ​ | $ | (150,580) | ​ | $ | 327,061 | ​ | $ | 628,774 | | $ | 805,666 | ​ |

| Net income | | — | ​ | | — | | — | ​ | | — | ​ | | — | ​ | | 245,947 | | | 245,947 | ​ |

| Issuance of restricted stock & performance stock | | — | ​ | | — | | 113,955 | ​ | | 3,657 | ​ | | (113) | ​ | | — | | | 3,544 | ​ |

| Share repurchase | | — | ​ | | — | | (442,049) | ​ | | (38,216) | ​ | | — | ​ | | — | | | (38,216) | ​ |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

| Payments on term loan | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (120,000) | ​ |

| Payments on finance lease liabilities | ​ | ​ | — | ​ | | — | ​ | ​ | (899) | ​ |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |

In November 2023, the FASB issued ASU 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures.” This standard requires entities to disclose, on an annual and interim basis, significant segment expenses that are regularly provided to the chief decision maker and included within each reported measure of segment profit and loss.

ASU 2023-07 is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024.

We adopted this standard beginning with our 2024

Early adoption is permitted.

We are currently evaluating the impact ASU 2024-03 will have on our disclosures; however, the standard will not have an impact on our consolidated financial position, results of operation or cash flow.

service financial assets due to lien rights, which we are more likely to have on construction jobs.

Losses are estimated and accrued based upon known facts, historical trends and industry averages.

Estimated losses in excess of our deductible, which have not already been paid, are included in our accrual

with a corresponding receivable from our insurance carrier.

We have a $6.8 million investment in a construction-focused technology fund with a fair value that is not readily determinable and is recorded at cost.

This investment is included in “Other Noncurrent Assets” in our Consolidated Balance Sheet and is reviewed quarterly for impairment.

We did not recognize any impairments in the current year related to this investment.

We do

obligations could change the amount of revenue and profit recorded in a given period.

| ​ | ​ | ​ | ​ | ​ | ​ |

| --- | --- | --- | --- | --- | --- |

Of the increase in contract assets, $59.9 million was driven by the timing of billings, which can sometimes be impacted by milestone billing agreements.

Additionally, acquisitions in 2024 increased contract assets by $3.7 million.

The increase in contract liabilities is primarily due to an increase of $207.5 million as a result of our 2024 acquisitions.

Unsettled amounts under our interest rate swaps, if any, are recorded in the Consolidated Balance Sheet at fair value in “Other Receivables” or “Other Current Liabilities.” Gains and losses on our interest rate swaps are recorded in the Consolidated Statement of Operations in “Interest Expense.” For the year ended December 31, 2022, we recognized a net gain of $0.3 million related to our interest rate swaps.

| Life insurance—cash surrender value | ​ | $ | — | ​ | $ | 7,473 | ​ | $ | — | ​ | $ | 7,473 |

The policies are invested in several investment vehicles, and the fair value measurement of the cash surrender balance associated with these policies is determined using Level 2 inputs within the fair value hierarchy and will vary with investment performance.

reporting period, and changes in estimates of fair value are recognized in earnings.

There have not been any changes in our internal control over financial reporting (as such term is defined in Rules 13a-15(f) and 15d-15(f) under the Securities Exchange Act of 1934) during the three months ended December 31, [removed: 2024] [added: 2025] that have materially affected, or are reasonably likely to materially affect, internal control over financial reporting.

Under the supervision and with the participation of our management, including our Chief Executive Officer and Chief Financial Officer, we conducted an evaluation of the effectiveness of our internal control over financial reporting as of December 31, [removed: 2024] [added: 2025] based on the framework in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO 2013 framework).

Based on that evaluation, our management concluded that our internal control over financial reporting was effective as of December 31, [removed: 2024.][added: 2025.]

Due to the recent nature of these business combinations, [removed: Summit, J&S] [added: Feyen Zylstra, Meisner, Right Way,] and [removed: Precision’s] [added: Century’s] internal control over financial reporting and related processes have not been fully integrated into the Company’s existing systems and internal control over financial reporting as of December 31, [removed: 2024.][added: 2025.]

As such, our management has excluded [removed: Summit, J&S] [added: Feyen Zylstra, Meisner, Right Way,] and [removed: Precision] [added: Century] from its assessment of the effectiveness of internal control over financial reporting as of December 31, [removed: 2024.][added: 2025.]

Collectively, [removed: Summit, J&S] [added: Feyen Zylstra, Meisner, Right Way] and [removed: Precision] [added: Century] comprised [removed: 12.6%] [added: 7.0%] of total assets and [removed: 9.0%] [added: 2.2%] of revenues in our consolidated financial statements as of and for the year ended December 31, [removed: 2024.][added: 2025.]

Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report which is included elsewhere herein, has issued an attestation report auditing the effectiveness of our internal control over financial reporting as of December 31, [removed: 2024.][added: 2025.]

We have audited the internal control over financial reporting of Comfort Systems USA, Inc and subsidiaries (the “Company”) as of December 31, [removed: 2024,] [added: 2025,] based on criteria established in _Internal Control — Integrated Framework (2013)_ issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, [removed: 2024,] [added: 2025,] based on criteria established in _Internal Control — Integrated Framework (2013)_ issued by COSO.

We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the consolidated financial statements as of and for the year ended December 31, [removed: 2024,] [added: 2025, of the Company] and our report dated February [removed: 20, 2025,] [added: 19, 2026,] expressed an unqualified opinion on those financial statements.

As described in Management’s Report on Internal Control over Financial Reporting, management excluded from its assessment the internal control over financial reporting at [removed: J&S Mechanical Contractors,] [added: Feyen-Zylstra Holdings, LLC (“Feyen Zylstra”) (acquired October 1, 2025), Meisner Electric,] Inc. [removed: (“J&S”)] [added: (“Meisner”)] (acquired [removed: February] [added: October] 1, [removed: 2024), Summit Industrial Construction,] [added: 2025), Right Way Plumbing & Mechanical] LLC [removed: (“Summit”)] [added: (“Right Way”)] (acquired [removed: February] [added: May] 1, [removed: 2024), and Precision Plumbing] [added: 2025)] and [removed: Service,] [added: Century Contractors,] LLC [removed: (“Precision”)] [added: (“Century”)] (acquired [removed: May] [added: January] 1, [removed: 2024)] [added: 2025)] and whose financial statements collectively constitute [removed: 12.6%] [added: 7.0%] of total assets and [removed: 9.0%] [added: 2.2%] of total revenues in the consolidated financial statement amounts as of and for the year ended December 31, [removed: 2024.][added: 2025.]

Accordingly, our audit did not include the internal control over financial reporting at [removed: J&S, Summit,] [added: Feyen Zylstra, Meisner, Right Way] and [removed: Precision.][added: Century.]

The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management’s Report on Internal [removed: Control.][added: Controls.]

The Company acquired Feyen-Zylstra Holdings, LLC and Meisner Electric, Inc. in October 2025, Right Way Plumbing & Mechanical LLC in May 2025 and Century Contractors, LLC in January 2025.

February 19, 2026

The Company acquired Summit Industrial Construction, LLC and J & S Mechanical, Inc. in February 2024 and Precision Plumbing and Service, LLC in May 2024.

February 20, 2025

During the three months ended December 31, [removed: 2024,] [added: 2025,] no directors or officers of the Company adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as defined in Item 408(a) and (c) of Regulation S-K.

The other information required by this Item 10 will be furnished on or prior to May 1, [removed: 2025] [added: 2026] (and is hereby incorporated by reference) by an amendment hereto or pursuant to a definitive proxy statement involving the election of directors pursuant to Regulation 14A that will contain such information.

The information required by Items 11, 12, 13 and 14 will be furnished on or prior to May 1, [removed: 2025] [added: 2026] (and is hereby incorporated by reference) by an amendment hereto or pursuant to a definitive proxy statement involving the election of directors pursuant to Regulation 14A that will contain such information.

| ExhibitNumber | [added: ​ ​ ​] | | Description of Exhibits | [added: ​ ​ ​] | ExhibitNumber | [added: ​ ​ ​] | Filing or File Number | |

| [removed: 10.9] [added: 10.8] | ​ | | [Amendment No. 3 to Second Amended and Restated Credit Agreement and Amendment to Other Loan Documents](http://www.sec.gov/Archives/edgar/data/1035983/000104746914008664/a2221896zex-10_1.htm) | ​ | 10.1 | ​ | Third Quarter 2014 Form 10-Q | |

| [removed: 10.10] [added: 10.9] | ​ | | [Agreement and Plan of Merger between the Company and Dyna Ten Corporation, dated April 7, 2014](http://www.sec.gov/Archives/edgar/data/1035983/000110465914026747/a14-10230_1ex10d1.htm) | ​ | 10.1 | ​ | April 9, 2014 Form 8-K | |

| [removed: *10.11] [added: *10.10] | ​ | | [Form of Amended Change in Control Agreement](http://www.sec.gov/Archives/edgar/data/1035983/000104746915008149/a2226337zex-10_1.htm) | ​ | 10.1 | ​ | Third Quarter 2015 Form 10-Q | |

| [removed: 10.12] [added: 10.11] | ​ | | [Amendment No. 4 to Second Amended and Restated Credit Agreement and Amendment to Other Loan Documents](http://www.sec.gov/Archives/edgar/data/1035983/000104746916010332/a2227387zex-10_40.htm) | ​ | [removed: 10.40] [added: 10.1] | ​ | 2015 Form 10-K | |

| [removed: *10.13] [added: *10.12] | ​ | | [Form of 2016 Stock Option Notice](http://www.sec.gov/Archives/edgar/data/1035983/000110465916107645/a16-7178_1ex10d3.htm) | ​ | 10.3 | ​ | March 25, 2016 Form 8-K | |

| [removed: *10.14] [added: *10.13] | ​ | | [Resignation and General Release Agreement between the Company and James Mylett, dated as of January 10, 2017](http://www.sec.gov/Archives/edgar/data/1035983/000110465917001957/a17-1811_1ex10d1.htm) | ​ | 10.1 | ​ | January 11, 2017 Form 8-K | |

| [removed: 10.15] [added: 10.14] | ​ | | [Stock Purchase Agreement, dated February 21, 2017, by and among the Company, BCH, the Selling Shareholders and Daryl Blume, in his capacity as representative of the Selling Shareholders](http://www.sec.gov/Archives/edgar/data/1035983/000110465917011244/a17-7023_1ex2d1.htm) | ​ | 2.1 | ​ | | February 23, 2017 Form 8-K |

| ExhibitNumber | [added: ​ ​ ​] | | Description of Exhibits | [added: ​ ​ ​] | ExhibitNumber | [added: ​ ​ ​] | Filing or File Number | |

| [removed: 10.16] [added: 10.15] | ​ | | [Form of Promissory Note, dated April 1, 2017, issued by the Company in favor of each of the Selling Shareholders](http://www.sec.gov/Archives/edgar/data/1035983/000110465917020991/a17-10800_1ex10d1.htm) | ​ | 10.1 | ​ | | April 3, 2017 Form 8-K |

| [removed: *10.17] [added: *10.16] | ​ | | [2017 Omnibus Incentive Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837017002563/fix-20170523xdef14a.htm) | ​ | A | ​ | | April 10, 2017 Proxy Statement |

| [removed: *10.18] [added: *10.17] | ​ | | [2017 Senior Management Annual Performance Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837017002563/fix-20170523xdef14a.htm) | ​ | B | ​ | | April 10, 2017 Proxy Statement |

| [removed: *10.19] [added: *10.18] | ​ | | [Form of Restricted Stock Unit Agreement under the Company’s [removed: 2012 Equity] [added: 2017 Omnibus] Incentive [removed: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837017002931/fix-20170331ex102e9479d.htm)] [added: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837018003336/fix-20180331ex101c8a191.htm)] | ​ | [removed: 10.2] [added: 10.1] | ​ | | First Quarter [removed: 2017] [added: 2018] Form 10-Q |

| [removed: *10.20] [added: *10.19] | ​ | | [Form of Stock Option Notice under the Company’s [removed: 2012 Equity] [added: 2017 Omnibus] Incentive [removed: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837017002931/fix-20170331ex103bc199c.htm)] [added: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837018003336/fix-20180331ex102ce3cf4.htm)] | ​ | [removed: 10.3] [added: 10.2] | ​ | | First Quarter [removed: 2017] [added: 2018] Form 10-Q |

| [removed: *10.21] [added: *10.20] | ​ | | [Form of Dollar-denominated Performance Restricted Stock Unit Agreement under the Company’s [removed: 2012 Equity] [added: 2017 Omnibus] Incentive [removed: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837017002931/fix-20170331ex104628293.htm)] [added: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837018003336/fix-20180331ex10323834b.htm)] | ​ | [removed: 10.4] [added: 10.3] | ​ | | First Quarter [removed: 2017] [added: 2018] Form 10-Q |

| [removed: *10.22] [added: *10.28] | ​ | | [Form of Restricted Stock Unit Agreement [added: with Revisions] under the Company’s 2017 Omnibus Incentive [removed: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837018003336/fix-20180331ex101c8a191.htm)] [added: Plan](https://www.sec.gov/Archives/edgar/data/1035983/000155837023006827/fix-20230331xex10d1.htm)] | ​ | 10.1 | ​ | | First Quarter [removed: 2018] [added: 2023] Form 10-Q |

| [removed: *10.23] [added: *10.29] | ​ | | [Form of [added: Dollar-denominated Performance Restricted] Stock [removed: Option Notice] [added: Unit Agreement with Revisions] under the Company’s 2017 Omnibus Incentive [removed: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837018003336/fix-20180331ex102ce3cf4.htm)] [added: Plan](https://www.sec.gov/Archives/edgar/data/1035983/000155837023006827/fix-20230331xex10d2.htm)] | ​ | 10.2 | ​ | | First Quarter [removed: 2018] [added: 2023] Form 10-Q |

| [removed: *10.24] [added: *10.27] | ​ | | [Form of [removed: Dollar-denominated Performance] Restricted Stock Unit Agreement [added: with a Blank Vesting Schedule] under the Company’s 2017 Omnibus Incentive [removed: Plan](http://www.sec.gov/Archives/edgar/data/1035983/000155837018003336/fix-20180331ex10323834b.htm)] [added: Plan](https://www.sec.gov/Archives/edgar/data/1035983/000155837022011139/fix-20220630xex10d2.htm)] | ​ | [removed: 10.3] [added: 10.2] | ​ | | [removed: First] [added: Second] Quarter [removed: 2018] [added: 2022] Form 10-Q |

| [removed: 10.25] [added: 10.21] | ​ | | [Amendment No. 5 to Second Amended and Restated Credit Agreement and Amendment to Other Loan Documents](http://www.sec.gov/Archives/edgar/data/1035983/000155837018005771/fix-20180630ex1010b4b06.htm) | ​ | 10.1 | ​ | | Second Quarter 2018 Form 10-Q |

| [removed: 10.26] [added: 10.22] | ​ | | [Purchase Agreement, dated February 21, 2019, by and among the Company, Walker, the Shareholder Sellers and Scott Walker, in his capacity as representative of the Shareholder Sellers](https://www.sec.gov/Archives/edgar/data/1035983/000110465919010746/a19-5185_2ex2d1.htm) | ​ | 2.1 | ​ | | February 26, 2019 Form 8-K |

| [removed: 10.27] [added: 10.23] | ​ | | [Amendment No. 6 to Second Amended and Restated Credit Agreement and Amendment to Other Loan Documents](https://www.sec.gov/Archives/edgar/data/1035983/000155837020001491/ex-10d56.htm) | ​ | 10.56 | ​ | | 2019 Form 10-K |

| [removed: 10.28] [added: 10.24] | ​ | | [Agreement and Plan of Merger dated as of March 9, 2020 among Comfort Systems USA, Inc., OSC Acquisition Corp., TAS Energy Inc., and Element Partners II, L.P., as Stockholder Representative](https://www.sec.gov/Archives/edgar/data/1035983/000110465920033252/tm2012107d1_ex2-1.htm) | ​ | 2.1 | ​ | | March 13, 2020 Form 8-K |

| [removed: *10.29] [added: *10.25] | ​ | | [Resignation and General Release Agreement between Comfort Systems USA, Inc. and Terrence Young, dated as of January 18, 2022](https://www.sec.gov/Archives/edgar/data/1035983/000110465922005448/tm222551d2_ex10-1.htm) | ​ | 10.1 | ​ | | January 19, 2022 Form 8-K |

| [removed: 10.30] [added: 10.26] | ​ | | [Third Amended and Restated Credit Agreement dated as of May 25, 2022 by and among Comfort Systems USA, Inc., as Borrower, the Lenders listed on the signature pages thereof, and Wells Fargo Bank, National Association, as Agent for the Lenders](https://www.sec.gov/Archives/edgar/data/1035983/000110465922065983/tm2217125d1_ex10-1.htm) | ​ | 10.1 | ​ | | May 27, 2022 Form 8-K/A |

| [removed: *10.31] [added: *10.30] | ​ | | [Form of Restricted Stock Unit Agreement [removed: with a Blank] [added: without “Rule of 75”] Vesting [removed: Schedule] under the Company’s 2017 Omnibus Incentive [removed: Plan](https://www.sec.gov/Archives/edgar/data/1035983/000155837022011139/fix-20220630xex10d2.htm)] [added: Plan](https://www.sec.gov/Archives/edgar/data/1035983/000155837024001529/fix-20231231xex10d34.htm)] | ​ | [removed: 10.2] [added: 10.34] | ​ | | [removed: Second Quarter 2022] [added: 2023] Form [removed: 10-Q] [added: 10-K] |

| 19 | ​ | | [Insider Trading Window [removed: Policy](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex19.htm)] [added: Policy](https://www.sec.gov/Archives/edgar/data/1035983/000110465926017530/fix-20251231xex19.htm)] | ​ | ​ | ​ | | Filed Herewith |

| 21.1 | ​ | | [List of subsidiaries of Comfort Systems USA, [removed: Inc.](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex21d1.htm)] [added: Inc.](https://www.sec.gov/Archives/edgar/data/1035983/000110465926017530/fix-20251231xex21d1.htm)] | ​ | ​ | ​ | | Filed Herewith |

| 23.1 | ​ | | [Consent of Deloitte & Touche [removed: LLP](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex23d1.htm)] [added: LLP](https://www.sec.gov/Archives/edgar/data/1035983/000110465926017530/fix-20251231xex23d1.htm)] | ​ | ​ | ​ | | Filed Herewith |

| 31.1 | ​ | | [Certification of Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of [removed: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex31d1.htm)] [added: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000110465926017530/fix-20251231xex31d1.htm)] | ​ | ​ | ​ | | Filed Herewith |

| 31.2 | ​ | | [Certification of Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of [removed: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex31d2.htm)] [added: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000110465926017530/fix-20251231xex31d2.htm)] | ​ | ​ | ​ | | Filed Herewith |

| 32.1 | ​ | | [Certification of Chief Executive Officer pursuant to Section 906 of the Sarbanes-Oxley Act of [removed: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex32d1.htm)] [added: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000110465926017530/fix-20251231xex32d1.htm)] | ​ | ​ | ​ | | Furnished Herewith |

| ExhibitNumber | [added: ​ ​ ​] | | Description of Exhibits | [added: ​ ​ ​] | ExhibitNumber | [added: ​ ​ ​] | Filing or File Number | |

| 32.2 | ​ | | [Certification of Chief Financial Officer pursuant to Section 906 of the Sarbanes-Oxley Act of [removed: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex32d2.htm)] [added: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000110465926017530/fix-20251231xex32d2.htm)] | ​ | ​ | ​ | | Furnished Herewith |

| ​ | ​ | [removed: _President and Chief] [added: _Chief] Executive Officer_ |

| Date: February [removed: 20, 2025] [added: 19, 2026] | ​ | ​ |

| Signature | [added: ​ ​ ​] | Title | [added: ​ ​ ​] | Date | |

| /s/ Brian E. Lane | ​ | [removed: President,] Chief Executive [removed: Officer,] [added: Officer] and [added: Director] | ​ | February [removed: 20, 2025] [added: 19, 2026] | ​ |

| Brian E. Lane | ​ | [removed: Director] (Principal Executive Officer) | ​ | ​ | ​ |

| /s/ William George | ​ | Executive Vice President and Chief Financial | ​ | February [removed: 20, 2025] [added: 19, 2026] | ​ |

| /s/ Julie S. Shaeff | ​ | Senior Vice President and Chief Accounting | ​ | February [removed: 20, 2025] [added: 19, 2026] | ​ |

| 10.31 | ​ | | [Fourth Amended and Restated Credit Agreement dated as of August 27, 2025 by and among Comfort Systems USA, Inc. as Borrower, the Lenders listed on the signature pages thereof, and Wells Fargo Bank, National Association, as Agent for the Lenders](https://www.sec.gov/Archives/edgar/data/1035983/000110465925086404/tm2524764d1_ex10-1.htm) | ​ | 10.1 | ​ | | September 2, 2025 Form 8-K |

| 10.32 | ​ | | [Fourth Amended and Restated Credit Agreement dated as of August 27, 2025 by and among Comfort Systems USA, Inc. as Borrower, the Lenders listed on the signature pages thereof, and Wells Fargo Bank, National Association, as Agent for the Lenders](https://www.sec.gov/Archives/edgar/data/1035983/000110465926017530/fix-20251231xex10d32.htm) | ​ | 10.32 | ​ | | Filed Herewith |

| *10.8 | ​ | | [Form of Option Award under the Comfort Systems USA, Inc. 2012 Equity Incentive Plan](http://www.sec.gov/Archives/edgar/data/1035983/000104746915001294/a2223211zex-10_33.htm) | ​ | 10.33 | ​ | 2014 Form 10-K | |

| *10.32 | ​ | | [Form of Restricted Stock Unit Agreement with Revisions under the Company’s 2017 Omnibus Incentive Plan](https://www.sec.gov/Archives/edgar/data/1035983/000155837023006827/fix-20230331xex10d1.htm) | ​ | 10.1 | ​ | | First Quarter 2023 Form 10-Q |

| *10.33 | ​ | | [Form of Dollar-denominated Performance Restricted Stock Unit Agreement with Revisions under the Company’s 2017 Omnibus Incentive Plan](https://www.sec.gov/Archives/edgar/data/1035983/000155837023006827/fix-20230331xex10d2.htm) | ​ | 10.2 | ​ | | First Quarter 2023 Form 10-Q |

| *10.34 | ​ | | [Form of Restricted Stock Unit Agreement without “Rule of 75” Vesting under the Company’s 2017 Omnibus Incentive Plan](https://www.sec.gov/Archives/edgar/data/1035983/000155837024001529/fix-20231231xex10d34.htm) | ​ | 10.34 | ​ | | 2023 Form 10-K |

| ​ | ​ | ​ | ​ | ​ | ​ |

| /s/ Vance W. Tang | ​ | Director | ​ | February 20, 2025 | ​ |

| Vance W. Tang | ​ | ​ | ​ | ​ | ​ |