Comfort Systems USA (FIX) 10-K risk factor changes: FY2024 vs FY2023

Any period of economic recession affecting a market or industry in which we [added: transact business is likely to adversely impact our business.]

Additionally, because [removed: 5.8%] [added: 5.4%] of our revenue for the year ended December 31, [removed: 2023] [added: 2024] was attributable to projects in the government sector, a reduction in federal, state, or local government spending in our industries and markets could result in decreased revenue and profit for us.

Our backlog as of December 31, [removed: 2023] [added: 2024] was [removed: $5.16] [added: $5.99] billion.

The global economy [removed: has recently experienced] [added: 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, [added: unrest in] the [removed: war between Israel and Hamas,] [added: Middle East,] and supply chain constraints.

In efforts to combat inflation, the U.S. Federal Reserve raised interest rates multiple times in recent years and may do so again in [removed: 2024] [added: 2025] (or may slow any rate reductions from what the market currently anticipates).

For instance, we have exposure to changes in interest rates under our revolving credit [removed: facility] [added: facility,] and as interest rates increase, our debt service obligations on our variable rate indebtedness will increase even though the amount borrowed remains the same, and our net income and cash flows, including cash available for servicing our indebtedness, may correspondingly decrease.

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

[added: If our surety companies] were to limit or eliminate our access to bonds, our alternatives would include seeking bonding capacity from other surety companies, increasing business with clients that do not require bonds and posting other forms of collateral for project performance, such as letters of credit or cash.

We may need to perform our work under a variety of conditions, including but not limited to, difficult terrain, difficult site conditions and busy urban centers where delivery of materials and availability of labor may be impacted, clean-room environments where strict procedures must be followed and sites that may have been exposed to harsh and hazardous conditions and outbreaks of infectious [removed: disease, such as the COVID-19 pandemic.][added: disease.]

Physical risks from climate change could, among other things, include an increase in extreme weather events (such as [added: wildfires,] floods [removed: or] [added: and] hurricanes), rising sea levels and limitations on water availability and quality.

The last several years have been periodically marked by political and economic concerns, including the COVID-19 pandemic, decreased consumer confidence, the effects of international conflicts such as the wars between Russia and Ukraine and [removed: between Israel and Hamas,] [added: unrest in the Middle East,] tariffs, energy costs and inflation.

Further, ongoing economic instability in the global markets, [removed: including from the COVID-19 pandemic,] supply chain disruptions, rising inflation and interest rates and the wars between Russia and Ukraine and [removed: between Israel and Hamas,] [added: unrest in the Middle East,] could limit our ability to access the capital markets at a time when we would like, or need, to raise capital, which could have an impact on our ability to react to changing business conditions or new opportunities.

If our business resources become strained or over-burdensome, our earnings may be adversely affected, and we may be unable to increase revenue [added: growth.]

Any of these events could damage our reputation [removed: and, while the April 2019 incident did not have such effects,] [added: and] have a material adverse effect on our business, results of operations, financial condition and cash flows.

[added: The implementation of new systems and information] technology could adversely impact our operations by requiring substantial capital expenditures, diverting management’s attention, or causing delays or difficulties in transitioning to new systems.

[removed: If we are unable to] service our debt obligations or fund our other liquidity needs, we could be forced to curtail our operations, reorganize our capital structure (including through bankruptcy proceedings) or liquidate some or all of our assets in a manner that could cause holders of our securities to experience a partial or total loss of their investment in us.

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

Our [removed: 172] [added: 178] locations are located in 27 states, which exposes us to a variety of different state and local laws and regulations, particularly those pertaining to contractor licensing requirements.

Because [removed: 5.8%] [added: 5.4%] of our revenue for the year ended December 31, [removed: 2023] [added: 2024] was attributable to projects in the government sector, prohibitions against bidding on future government contracts could have an adverse effect on our financial condition and results of operations.

Each location is subject to numerous safety risks, including fall risks, electrocutions, fires, explosions, mechanical failures, weather-related incidents, transportation accidents, damage to equipment and, with respect to indoor sites, an increased risk of [removed: COVID-19 outbreaks.][added: infectious disease.]

While we have taken what we believe are appropriate precautions to minimize safety [removed: risks,] [added: risks and continuously focus on adopting improved safety practices,] we have experienced serious accidents, including fatalities, in the past and may experience additional accidents in the future.

For example, the U.S. government has [removed: recently pursued a new] [added: adopted an evolving] approach to trade policy, including renegotiating or terminating certain existing bilateral or multi-lateral trade agreements.

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

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 [removed: products,] [added: 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.

Our results of operations are reported based on our determination of the amount of taxes we owe in various tax jurisdictions, and our provision for income taxes and tax liabilities are subject to review or examination by taxing authorities in applicable tax [removed: jurisdictions.]

An adverse outcome of such a review or examination could adversely affect our operating results and [added: financial condition.]

Force majeure or extraordinary events beyond the control of the contracting parties, such as natural and man-made disasters, as well as outbreaks of infectious disease [removed: (e.g.,] [added: (_e.g._,] COVID-19) and terrorist actions, could negatively impact us.

We typically negotiate contract language through which we are granted certain relief from force majeure [removed: events in private client contracts and review and attempt to mitigate force majeure events in both public and private]

The loss of one or a few customers could adversely affect our business, financial condition and results of operations.

A few customers have in the past and may in the future account for a significant portion of our revenues.

For example, in 2024, one customer represented approximately 13.3% of our consolidated revenue.

Although we have

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

A loss of business from a significant customer, or a number of significant customers, could have a material adverse effect on our business, financial condition, results of operations and cash flows.

terms have become more expensive and more restrictive.

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.

If we are unable to

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.

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.

jurisdictions.

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

transact business is likely to adversely impact our business.

If our surety companies

growth.

In April 2019, for example, our information technology infrastructure was impacted by a ransomware attack virus, which caused a substantial majority of our operating locations to experience loss of access to certain data and outages affecting systems including accounting, payroll, billing, job report and management and other software environments.

These disruptions created challenges in key back-office functions that required workarounds and alternative procedures.

The implementation of new systems and information

Future legislation could also have an impact on our business.

financial condition.

client contracts.

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

We also perform electrical logistics [removed: services, electrical service work,] [added: services] and electrical [removed: construction and engineering services.][added: service work.]

Approximately [removed: 89.0%] [added: 91.1%] of our revenue is earned on a project basis for installation services in newly constructed facilities or for replacement of systems in existing facilities.

Project contracts typically provide for periodic billings to the customer as we meet progress milestones or incur [removed: cost] [added: costs] on the project.

As of December 31, [removed: 2023,] [added: 2024,] we had [removed: 10,481] [added: 7,935] projects in process.

Our average project takes six to nine months to complete, with an average contract price of approximately [removed: $1.1] [added: $1.8] 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 [removed: developments in any given sector.]

Taken together, projects with contract prices of $2 million or more totaled [removed: $10.2] [added: $12.78] billion of aggregate contract value as of December 31, [removed: 2023,] [added: 2024,] or approximately [removed: 86%,] [added: 89%,] out of a total contract value for all projects in progress of [removed: $12.0] [added: $14.35] billion.

A stratification of projects in progress as of December 31, [removed: 2023,] [added: 2024,] by contract price, is as follows:

| $10 million - $20 million | | [removed: 125] [added: 138] | ​ | | [removed: 1,761.0] [added: 1,947.4] | ​ |

| $20 million - $40 million | | [removed: 96] [added: 114] | ​ | | [removed: 2,688.2] [added: 3,253.0] | ​ |

| Greater than $40 million | | [removed: 40] [added: 68] | ​ | | [removed: 2,448.7] [added: 4,343.3] | ​ |

In addition to project work, approximately [removed: 11.0%] [added: 8.9%] of our revenue represents maintenance and repair service on already installed HVAC, electrical, and controls systems.

We manage our [removed: 44] [added: 47] operating units based on a variety of factors.

[added: With larger amounts of capital,] time, and discretion involved, spending decisions are affected to a significant degree by uncertainty, particularly concerns about economic and financial conditions and trends.

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

[removed: Although we have largely recovered from negative] [added: While the] impacts [removed: caused by] [added: from] the [removed: COVID-19 pandemic,] [added: supply chain shortages have improved,] we continue to experience increased labor [removed: costs, supply constraints and cost increases,] [added: costs] and delays in delivery of [removed: various] [added: certain] materials and equipment.

We expect that constraints and delays [added: in our supply chain] will continue to abate in [removed: 2024;] [added: the near term;] however, we anticipate that pressure on cost and availability, especially for skilled labor, will continue [removed: throughout 2024.][added: in 2025.]

As of December 31, [removed: 2023,] [added: 2024,] we had [removed: $779.8] [added: $770.0] million of credit available to borrow under our credit facility.

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

[removed: Variations from] estimated project costs could have a significant impact on our operating results, depending on project size, and the recoverability of the variation from change orders collected from customers.

Significant judgments and estimates are required in the determination of our income taxes, including the ability to recover our [added: deferred tax assets based on assumptions about future taxable income.]

| ​ | ​ | [removed: 2023] [added: 2024] | | | | | [removed: 2022] [added: 2023] | | | | | [removed: 2021] [added: 2022] | | | | ​ |

| Revenue | ​ | $ | [removed: 5,206,760] [added: 7,027,476] | | 100.0 | % | $ | [removed: 4,140,364] [added: 5,206,760] | | 100.0 | % | $ | [removed: 3,073,636] [added: 4,140,364] | | 100.0 | % |

| Cost of services | ​ | | [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] | % | | [removed: 2,510,429] [added: 3,398,756] | | [removed: 81.7] [added: 82.1] | % |

| Gross profit | ​ | | [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] | % | | [removed: 563,207] [added: 741,608] | | [removed: 18.3] [added: 17.9] | % |

| Selling, general and administrative expenses | ​ | | [removed: 574,423] [added: 730,072] | | [removed: 11.0] [added: 10.4] | % | | [removed: 489,344] [added: 574,423] | | [removed: 11.8] [added: 11.0] | % | | [removed: 376,309] [added: 489,344] | | [removed: 12.2] [added: 11.8] | % |

| Gain on sale of assets | ​ | | [removed: (2,302)] [added: (3,030)] | | — | ​ | | [removed: (1,585)] [added: (2,302)] | | — | ​ | | [removed: (1,540)] [added: (1,585)] | | [removed: (0.1)] [added: —] | [removed: %] [added: ​] |

| Operating income | ​ | | [removed: 418,388] [added: 749,369] | | [removed: 8.0] [added: 10.7] | % | | [removed: 253,849] [added: 418,388] | | [removed: 6.1] [added: 8.0] | % | | [removed: 188,438] [added: 253,849] | | 6.1 | % |

| Interest income | ​ | | [removed: 3,492] [added: 11,554] | | [removed: 0.1] [added: 0.2] | % | | [removed: 46] [added: 3,492] | | [removed: —] [added: 0.1] | [removed: ​] [added: %] | | [removed: 24] [added: 46] | | — | ​ |

| Interest expense | ​ | | [removed: (10,281)] [added: (6,648)] | | [removed: (0.2)] [added: (0.1)] | % | | [removed: (13,352)] [added: (10,281)] | | [removed: (0.3)] [added: (0.2)] | % | | [removed: (6,196)] [added: (13,352)] | | [removed: (0.2)] [added: (0.3)] | % |

| Changes in the fair value of contingent earn-out obligations | ​ | | [removed: (23,607)] [added: (88,146)] | | [removed: (0.5)] [added: (1.3)] | % | | [removed: (4,819)] [added: (23,607)] | | [removed: (0.1)] [added: (0.5)] | % | | [removed: 7,820] [added: (4,819)] | | [removed: 0.3] [added: (0.1)] | % |

| Other income | ​ | | [removed: 202] [added: 432] | | — | ​ | | [removed: 134] [added: 202] | | — | ​ | | [removed: 188] [added: 134] | | — | ​ |

| Income before income taxes | ​ | | [removed: 388,194] [added: 666,561] | | [removed: 7.5] [added: 9.5] | % | | [removed: 235,858] [added: 388,194] | | [removed: 5.7] [added: 7.5] | % | | [removed: 190,274] [added: 235,858] | | [removed: 6.2] [added: 5.7] | % |

| Provision (benefit) for income taxes | ​ | | [removed: 64,796] [added: 144,128] | ​ | ​ | ​ | | [removed: (10,089)] [added: 64,796] | ​ | ​ | ​ | | [removed: 46,926] [added: (10,089)] | ​ | ​ | ​ |

| Net income | ​ | $ | [removed: 323,398] [added: 522,433] | ​ | ​ | ​ | $ | [removed: 245,947] [added: 323,398] | ​ | ​ | ​ | $ | [removed: 143,348] [added: 245,947] | ​ | ​ | ​ |

We had [removed: 42] [added: 47] operating locations as of December 31, [removed: 2022.][added: 2024.]

The same-store comparison from [removed: 2023] [added: 2024] to [removed: 2022,] [added: 2023,] as described below, excludes [removed: Eldeco,] [added: Summit,] which was acquired on February 1, [removed: 2023,] [added: 2024, J&S, which was acquired on February 1, 2024, nine months of results for] DECCO, [added: Inc. (“DECCO”),] which was acquired on October 2, 2023, and [removed: three months] [added: one month] of results for [removed: Atlantic Electric, LLC (“Atlantic”),] [added: Eldeco, Inc (“Eldeco”),] which was acquired on [removed: April] [added: February] 1, [removed: 2022.][added: 2023.]

The increase included a [removed: 3.3%] [added: 12.1%] increase related to the [removed: Eldeco, DECCO] [added: Summit, J&S, DECCO,] and [removed: Atlantic] [added: Eldeco] acquisitions, as well as a [removed: 22.5%] [added: 22.9%] increase in revenue related to same-store activity.

The same-store revenue growth was largely driven by strong market [removed: conditions.][added: conditions, including the increase in our backlog.]

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 | ​ |

Variations from

2024 Compared to 2023

In the first quarter of 2024, we split one of our operating locations into two separate operating locations.

Additionally, we completed the acquisitions of Summit Industrial Construction, LLC (“Summit”) and J & S Mechanical Contractors, Inc. (“J&S”), which both report as separate operating locations.

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

| ​ | | 2024 | | | | | ​ | 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.

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).

| ​ | | 2024 | | | 2023 | | |

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

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

The increase in interest income is due to both an increase in our average cash balance and higher interest rates compared to the prior year.

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

The effective rate for 2024 was slightly higher than the 21% federal statutory rate primarily due to net state income taxes (3.9%) and nondeductible expenses (1.5%), partially offset by the credit for increasing research activities (the “R&D tax credit”) (4.1%).

We have a good pipeline of opportunities and potential backlog.

2024 Compared to 2023

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.

We thus made an $80.0 million federal tax payment in the first quarter of 2025 that otherwise would have been paid in the second half of 2024.

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.

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.

| 2025 | ​ | $ | 5,968 | ​ | 2.3 - 2.5 | % |

| 2028 | ​ | ​ | 5,000 | ​ | 5.5 | % |

| Total | ​ | $ | 67,593 | ​ | ​ | ​ |

​

| Notes to former owners | ​ | $ | 5,968 | ​ | $ | 30,625 | ​ | $ | 26,000 | ​ | $ | 5,000 | ​ | $ | — | ​ | $ | — | ​ | $ | 67,593 | ​ |

| Interest payable | ​ | | 3,314 | ​ | | 2,485 | ​ | | 1,038 | ​ | ​ | 56 | ​ | | 3 | ​ | | — | ​ | | 6,896 | ​ |

| Operating lease obligations | ​ | | 41,442 | ​ | | 37,819 | ​ | | 33,246 | ​ | | 29,286 | ​ | | 25,518 | ​ | | 170,630 | ​ | | 337,941 | ​ |

| Total | ​ | $ | 50,798 | ​ | $ | 71,001 | ​ | $ | 60,313 | ​ | $ | 34,364 | ​ | $ | 26,066 | ​ | $ | 170,630 | ​ | $ | 413,172 | ​ |

| Under $2 million | | 9,477 | ​ | $ | 1,722.1 | ​ |

| $2 million - $10 million | | 743 | ​ | | 3,346.2 | ​ |

| Total | | 10,481 | ​ | $ | 11,966.2 | ​ |

With larger amounts of capital,

deferred tax assets based on assumptions about future taxable income.

In the first quarter of 2023, we completed the acquisition of Eldeco, Inc. (“Eldeco”), which reports as a separate operating location.

In the fourth quarter of 2023, we completed the acquisition of DECCO, Inc. (“DECCO”), which reports as a separate operating location.

_Revenue_—Revenue increased $1.07 billion, or 25.8%, to $5.21 billion in 2023 compared to 2022.

The increase primarily resulted from the acquisition of Eldeco ($115.5 million), as well as an additional three months of revenue related to the Atlantic acquisition ($6.7 million).

The sequential backlog increase included the acquisition of DECCO ($29.7 million) as well as a same-store increase of $840.1 million, or 19.6%.

_Gross Profit_—Gross profit increased $248.9 million, or 33.6%, to $990.5 million in 2023 as compared to 2022.

Our overall margin increases were partially offset by growth in modular construction jobs in 2023, which have lower margins than any of our other businesses.

This increase was partially offset by a decrease in professional fees of $3.3 million as compared to the prior year related to the credit for increasing research activities (the “R&D tax credit”) for prior tax years.

| ​ | | December 31, | | | | | ​ |

| SG&A | ​ | $ | 574,423 | ​ | $ | 489,344 | ​ |

| Same-store SG&A, excluding amortization expense | ​ | $ | 520,200 | ​ | $ | 452,918 | ​ |

The increase in interest income is primarily due to interest awarded to us related to a dispute with a customer.

_Interest Expense_—Interest expense decreased $3.1 million, or 23.0%, in 2023 as compared to 2022.

The effective rate for

The effective rate for 2022 was significantly lower than the 21% federal statutory rate due to a reduction in net unrecognized tax benefits primarily from settlement with the Internal Revenue Service (the “IRS”) for 2016, 2017, and 2018 tax years (7.6%), the filing of returns to claim the R&D tax credit for 2019, 2020 and 2021 tax years (15.1%) and inclusion of the R&D tax credit for 2022 (6.7%).

These benefits were partially offset by net state income taxes (4.0%) and nondeductible expenses related to TAS Energy Inc. (1.7%).

As a result of conforming amendments made to the R&D tax credit in connection with the deferral of tax deductions for research and experimental (“R&E”) expenditures pursuant to the Tax Cuts and Jobs Act (2017), our provision for income taxes for the year ended December 31, 2023 benefited from a $10.0 million increase in the R&D tax credit.

Of the $10.0 million increase, $4.9 million related to the R&D tax credit for the 2022 tax year.

2022 Compared to 2021

| ​ | | 2023 | | | 2022 | | | 2021 | | |

deployed in project work until our customer pays us.

These increases were partially offset by a $158.4 million increase in receivables, net driven by higher revenue as compared to the prior year, a $107.1 million federal tax receivable, discussed further below, and $33.3 million of tax refunds received in 2022.

In early September 2023, the IRS issued interim guidance addressing, together with other topics, the treatment of R&E expenditures for taxpayers using the percentage of completion method to account for taxable income from long-term contracts.

We have chosen to rely on such guidance beginning with the 2022 tax year, and the resultant reduction in taxable revenue offsets the deferral of tax deductions for R&E expenditures for the 2022 tax year.

We filed our 2022 federal tax return in October 2023 requesting a refund of our $107.1 million overpayment, which was recorded in “Other Receivables” in our Balance Sheet as of December 31, 2023.

alternative to operating income, net income, or amounts shown in our Consolidated Statements of Cash Flows as determined under generally accepted accounting principles.

On May 25, 2022, 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, increasing our borrowing capacity to $850 million.

In 2022, we incurred approximately $2.3 million in financing and professional costs in connection with the amendment to the Facility, which, combined with previously unamortized costs of $1.2 million, are being amortized on a straight-line basis as a non-cash charge to interest expense over the remaining term of the Facility.

Certain of our vendors require letters of credit to ensure reimbursement for amounts they are disbursing on our behalf, such as to beneficiaries under our self-funded insurance programs.

We have also occasionally used letters of credit to guarantee performance under our contracts and to ensure payment to our subcontractors and vendors under those contracts.

A letter of credit commits the lenders to pay specified amounts to the holder of the letter of credit if the holder demonstrates that we have failed to perform specified actions.

Absent a claim, there is no payment or reserving of funds by us in connection with a letter of credit.

| 2024 | ​ | $ | 4,800 | ​ | 2.5 | % |

| 2025 | ​ | | 21,645 | ​ | 2.3 - 3.0 | % |

| Total | ​ | $ | 44,070 | ​ | ​ | ​ |

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: 2023:][added: 2024:]

| ​ | | [removed: 2024 | | |] 2025 | | | 2026 | | | 2027 | | | 2028 | | | [added: 2029] | | | [added: | | |] Thereafter | | | | | | Total | | | | | |

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

This analysis reflects the contractual terms of the purchase agreements [removed: (e.g.,] [added: (_e.g._,] minimum and maximum payment, length of earn-out periods, manner of calculating any amounts due, etc.) and utilizes assumptions with regard to future cash flows, probabilities of achieving such future cash flows and a discount rate.

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

| Average Interest Rate | ​ | | 5.0% | ​ | | 5.3% | ​ | | 5.5% | ​ | | 5.5% | ​ | | 6.0% | | | ​ | | | — | | | ​ | | | 5.4% | | | ​ | |

| Fixed Rate Debt | ​ | $ | 4,867 | ​ | $ | 21,701 | ​ | $ | 14,144 | ​ | $ | 3,500 | ​ | $ | — | | | ​ | | $ | — | | | ​ | | $ | 44,212 | | | ​ | |

| Average Interest Rate | ​ | | 3.2% | ​ | | 3.3% | ​ | | 4.3% | ​ | | 5.5% | ​ | | — | | | ​ | | | — | | | ​ | | | 3.8% | | | ​ | |

The weighted average interest rate applicable to the borrowings under the revolving credit facility was approximately 5.7% as of December 31, 2022.

We build, install, maintain, repair and replace mechanical, electrical and plumbing (“MEP”) systems throughout our [removed: 44] [added: 47] operating units with [removed: 172] [added: 178] locations in [removed: 131] [added: 136] cities throughout the United States.

Substantially all of our consolidated [removed: 2023] [added: 2024] revenue was derived from commercial, industrial and institutional customers and multi-family residential projects.

Approximately [removed: 54.8%] [added: 56.7%] of our revenue was attributable to installation services in newly constructed facilities and [removed: 45.2%] [added: 43.3%] was attributable to renovation, expansion, maintenance, repair and replacement services in existing buildings.

Our consolidated [removed: 2023] [added: 2024] revenue was derived from the following service industries:

| Mechanical Services | | [removed: 75.8] [added: 78.7] | % |

| Electrical Services | ​ | [removed: 24.2] [added: 21.3] | % |

We believe that commercial, industrial, and institutional mechanical and electrical contracting generate annual revenue in the United States of approximately [removed: $350] [added: $550] billion.

| | ● | construction of and installation in new buildings, which provided approximately [removed: 54.8%] [added: 56.7%] of our revenue in [removed: 2023,] [added: 2024,] and |

| | ● | renovation, expansion, maintenance, repair and replacement in existing buildings, which provided the remaining [removed: 45.2%] [added: 43.3%] of our [removed: 2023] [added: 2024] revenue. |

“Plan and spec” installation refers to projects in which a third-party architect or consulting engineer designs the MEP [removed: systems] [added: systems,] and the installation project is “put out for bid.” We believe that “plan and spec” projects usually take longer to complete and frequently result in less efficient outcomes than “design and build” projects because the system design and installation process are not integrated, thus resulting in more frequent adjustments to project specifications, work requirements and schedules.

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

these complex markets are attractive because of their growth opportunities, large and diverse customer [removed: base,] [added: bases,] attractive margins, and potential for long-term relationships with building owners.

_Leverage Resources and Capabilities_—We believe significant [removed: operating] efficiencies can be achieved by leveraging resources among our operating locations.

Our distribution of revenue in [removed: 2023] [added: 2024] by end-use sector was as follows:

| Office Buildings | | [removed: 7.7] [added: 6.0] | % |

| Retail, Restaurants and Entertainment | | [removed: 6.0] [added: 5.4] | % |

| Multi-Family and Residential | | [removed: 3.5] [added: 2.0] | % |

Approximately [removed: 89.0%] [added: 91.1%] of our revenue is earned on a project basis for installation of systems in newly constructed or existing facilities.

As of December 31, [removed: 2023,] [added: 2024,] we had [removed: 10,481] [added: 7,935] projects in process with an aggregate contract value of approximately [removed: $12.0] [added: $14.35] billion.

Our average project takes six to nine months to complete, with an average contract price of approximately [removed: $1.1] [added: $1.8] million.

This average project size, when taken together with the approximately [removed: 11.0%] [added: 8.9%] of our revenue derived from maintenance and service, provides us with a broad base of work in the construction services sector.

Accordingly, [removed: through our acquisitions,] we have invested in that [removed: capability,] [added: capability through acquisitions,] and after acquisition we have further invested in improving and growing that service offering.

Through [removed: recent and ongoing] development and acquisitions, we plan to continue to improve our unmatched capability in mechanical off-site or modular construction.

We have centralized certain administrative functions such as insurance, employee benefits, training, safety programs, [removed: marketing] and cash management to enable our local operating management to focus on pursuing new business opportunities and improving operating efficiencies.

_Construction and Installation Services for New Buildings_—Our installation business related to newly constructed facilities, which comprised approximately [removed: 54.8%] [added: 56.7%] of our consolidated [removed: 2023] [added: 2024] revenue, involves the design, engineering, integration, installation and start-up of MEP and related systems.

We also perform larger project work, with [removed: 1,004] [added: 1,046] contracts in progress at December 31, [removed: 2023] [added: 2024] with contract prices in excess of $2 million.

Our largest project in progress at December 31, [removed: 2023] [added: 2024] had a contract price of [removed: $149.6] [added: $168.9] million.

Project contracts typically provide for periodic billings to the customer as we meet progress milestones or incur [removed: cost] [added: costs] on the project.

_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: 45.2%] [added: 43.3%] of our consolidated [removed: 2023] [added: 2024] revenue.

However, during periods of peak demand, [removed: including recent residual effects of the COVID-19 pandemic,] lead-times for certain components may extend to several months.

We have procedures to reduce commodity cost [removed: exposure] [added: exposure, including costs due to tariffs,] such as purchasing commodities early for projects, as well as selectively including time or market-based escalation and escape provisions in bids and contracts.

The primary manufacturers of the major components in a commercial MEP system are: Trane, Carrier, York, Daikin (chillers and roof [removed: tops] [added: top] units), Baltimore Aircoil and SPX (cooling towers), Schneider Electric, Eaton, ABB (electrical switchgear), Caterpillar, Cummins, Kohler (power generators), Johnson Controls, Automated Logic and Siemens (building automation).

We have a diverse customer base, with our top customer representing [removed: 14%] [added: 13.3%] of consolidated [removed: 2023] [added: 2024] revenue.

_Employees_—As of December 31, [removed: 2023,] [added: 2024,] we had approximately [removed: 15,800] [added: 18,300] employees as compared to approximately [removed: 14,100] [added: 15,800] employees as of December 31, [removed: 2022.][added: 2023.]

We have collective bargaining agreements covering [removed: 7] [added: 50] employees.

_Culture and Core Values_—Our values define, inform, and guide the way we operate both within [removed: our] [added: the] Company and in the communities where we do business.

Everyone at [removed: our] [added: the] Company shares a responsibility for doing business ethically and in a sustainable manner, preserving our good name.

We provide numerous training programs for management, sales, and leadership, as well as on-the-job training, technical training, apprenticeship programs, attractive benefit packages and career advancement opportunities within [removed: our] [added: the] Company.

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: 1.10] [added: 0.97] during [removed: 2023.][added: 2024.]

[removed: To improve our competitive position, we] focus on both the consultative “design and build” installation market and the maintenance, repair, and replacement market to develop and strengthen customer relationships.

| Technology | ​ | 33.2 | % |

| Manufacturing | | 27.3 | % |

| Education | | 10.0 | % |

| Healthcare | | 8.3 | % |

| Government | | 5.4 | % |

| Other | | 2.4 | % |

Our average project takes six to nine months to complete, with an average contract price of approximately $1.8 million.

training.

To improve our competitive position, we

| Manufacturing | | 33.6 | % |

| Technology | ​ | 21.4 | % |

| Healthcare | | 10.6 | % |

| Education | | 9.5 | % |

| Government | | 5.8 | % |

| Other | | 1.9 | % |

trainings.

This level was 52% better than the most recently published OSHA rate for our industry.

Diversity and inclusion are among our leadership’s key priorities, including steps to accelerate progress in outreach, representation, development, and advancement of underrepresented groups within our Company.

In [removed: the first quarter of] 2023, we recorded a pre-tax gain of $6.8 million from legal developments and settlements that primarily relate to disputes with customers regarding the outcome of completed projects as well as an obligation to perform subcontract work under two executed letters of intent for subsequent projects that we believed were not enforceable.

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 [added: believed were not enforceable.]

As of December 31, [removed: 2023,] [added: 2024,] 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.

believed were not enforceable.

| For the fiscal year ended December 31, [removed: 2023] [added: 2024] | |

The aggregate market value of the voting stock held by non-affiliates of the registrant at June 30, [removed: 2023] [added: 2024] was approximately [removed: $5.75] [added: $10.67] billion, based on the [removed: $164.20] [added: $304.12] last sale price of the registrant’s common stock on the New York Stock Exchange on June 30, [removed: 2023.][added: 2024.]

As of February [removed: 16, 2024, 35,684,609] [added: 14, 2025, 35,553,062] shares of the registrant’s common stock were outstanding (excluding treasury shares of [removed: 5,438,756).][added: 5,570,303).]

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: 2023.][added: 2024.]

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

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

| [Item 9B.](#ITEM9BOtherInformation_701400) | [Other Information](#ITEM9BOtherInformation_701400) | [removed: 78] [added: 79] |

| [Item 9C.](#ITEM9CDisclosureRegardingForeignJurisdic) | [Disclosure Regarding Foreign Jurisdictions that Prevent Inspections](#ITEM9CDisclosureRegardingForeignJurisdic) | [removed: 78] [added: 79] |

| [Item 10.](#ITEM10DirectorsExecutiveOfficersandCorpo) | [Directors, Executive Officers and Corporate Governance](#ITEM10DirectorsExecutiveOfficersandCorpo) | [removed: 78] [added: 79] |

| [Item 11.](#ITEMS111213AND14_316091) | [Executive Compensation](#ITEMS111213AND14_316091) | [removed: 78] [added: 79] |

| [Item 12.](#ITEMS111213AND14_316091) | [Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters](#ITEMS111213AND14_316091) | [removed: 78] [added: 79] |

| [Item 13.](#ITEMS111213AND14_316091) | [Certain Relationships and Related Transactions, and Director Independence](#ITEMS111213AND14_316091) | [removed: 78] [added: 79] |

| [Item 14.](#ITEMS111213AND14_316091) | [Principal Accounting Fees and Services](#ITEMS111213AND14_316091) | [removed: 78] [added: 79] |

| [Item 15.](#ITEM15ExhibitsandFinancialStatementSched) | [Exhibits and Financial Statement Schedules](#ITEM15ExhibitsandFinancialStatementSched) | [removed: 78] [added: 79] |

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

Vance Tang, Chair of the Nominating, Governance, and Sustainability Committee, serves as the Board Liaison for Cybersecurity.

Mr. Tang has completed extensive training on cybersecurity risk mitigation, including certification related to completion of the NACD Cyber Risk Oversight Program.

As of December 31, [removed: 2023,] [added: 2024,] we owned [removed: 16] [added: 20] properties.

Lane,_ age [removed: 66,] [added: 67,] has served as our Chief Executive Officer and President since December 2011 and as a director since November 2010.

_William George,_ age [removed: 59,] [added: 60,] 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: 51,] [added: 52,] has served as Executive Vice President and Chief Operating Officer since January 2022 and was formerly Senior Vice President and Chief Operating Officer during 2021.

Shaeff,_ age [removed: 58,] [added: 59,] 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.

Howell,_ age [removed: 36,] [added: 37,] has served as Senior Vice President and General Counsel for the Company since January 2022 and formerly served as Vice President and General Counsel from January 2019 to December 2021.

[removed: 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.

_Terrence Reed_, age [removed: 64,] [added: 65,] 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 December 2023.

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

As of February [removed: 16, 2024,] [added: 14, 2025,] there were approximately [removed: 262] [added: 231] stockholders of record of our Common Stock, and the last reported sale price on that date was [removed: $248.50] [added: $391.22] per share.

[removed: ][added: ]

On [removed: May 17, 2022,] [added: August 7, 2024,] the Board approved an extension to the program by increasing the shares authorized for repurchase by [removed: 0.7] [added: 0.4] million shares.

Since the inception of the repurchase program, the Board has approved [removed: 10.9] [added: 11.4] million shares to be repurchased.

As of December 31, [removed: 2023,] [added: 2024,] we have repurchased a cumulative total of [removed: 10.3] [added: 10.4] million shares at an average price of [removed: $26.27] [added: $31.41] per share under the repurchase program.

During the year ended December 31, [removed: 2023,] [added: 2024,] we repurchased [removed: 0.1] [added: 0.2] million shares for approximately [removed: $21.3] [added: $58.3] million at an average price of [removed: $152.75] [added: $329.14] per share.

During the year ended December 31, [removed: 2023,] [added: 2024,] we purchased our common shares in the following amounts at the following average prices:

| | (1) | Purchased as part of a program announced on March 29, 2007 under which, since the inception of this program, [removed: 10.9] [added: 11.4] million shares have been approved for repurchase. |

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 | ​ |

| January 1 - January 31 | | 17,100 | ​ | $ | 116.89 | | 10,133,946 | | 810,179 | ​ |

| February 1 - February 28 | | 8,500 | ​ | $ | 122.13 | | 10,142,446 | | 801,679 | ​ |

| March 1 - March 31 | | 3,800 | ​ | $ | 139.69 | | 10,146,246 | | 797,879 | ​ |

| April 1 - April 30 | | 22,200 | ​ | $ | 132.20 | | 10,168,446 | | 775,679 | ​ |

| May 1 - May 31 | | 300 | ​ | $ | 149.28 | | 10,168,746 | | 775,379 | ​ |

| June 1 - June 30 | | 1,500 | ​ | $ | 152.26 | | 10,170,246 | | 773,879 | ​ |

| July 1 - July 31 | | 500 | ​ | $ | 154.60 | | 10,170,746 | | 773,379 | ​ |

| August 1 - August 31 | | — | ​ | $ | — | | 10,170,746 | | 773,379 | ​ |

| September 1 - September 30 | | 9,750 | ​ | $ | 175.37 | | 10,180,496 | | 763,629 | ​ |

| October 1 - October 31 | | 65,250 | ​ | $ | 164.81 | | 10,245,746 | | 698,379 | ​ |

| November 1 - November 30 | | 5,278 | ​ | $ | 186.26 | | 10,251,024 | | 693,101 | ​ |

| December 1 - December 31 | | 5,300 | ​ | $ | 189.79 | | 10,256,324 | | 687,801 | ​ |

| ​ | | 139,478 | ​ | $ | 152.75 | | 10,256,324 | | 687,801 | ​ |

We have audited the accompanying consolidated balance sheets of Comfort Systems USA, Inc. and [removed: its consolidated] subsidiaries (the “Company”) as of December 31, [removed: 2023] [added: 2024] and [removed: 2022,] [added: 2023,] the related consolidated statements of operations, stockholders’ equity, and cash flows, for each of the three years in the period ended December 31, [removed: 2023,] [added: 2024,] 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: 2023] [added: 2024] and [removed: 2022,] [added: 2023,] and the results of its operations and its cash flows for each of the three years in the period ended December 31, [removed: 2023,] [added: 2024,] 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: 2023,] [added: 2024,] 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: 22, 2024,] [added: 20, 2025,] 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 [added: 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 [added: consolidated] financial statements and (2) involved our especially challenging, subjective, or complex judgments.

The communication of this critical audit matter does not alter in any way our opinion on the [added: 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.

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

Our audit procedures related to management’s estimates and judgments included within the Company’s estimated total costs at [removed: contract] completion for its contracts with customers included the following, among others:

| ● | We evaluated [removed: quarter-over-quarter] [added: quarter over quarter] changes in contract profit estimates for a selection of contracts by obtaining explanations from Company’s management regarding the timing and amount of the changes in estimates and corroborating these inquiries by inspecting documents, including management [removed: workplans,] [added: work plans,] customer communications, change orders, vendor invoices, and supplier or subcontractor communications. |

| | ◾ | Evaluating management’s estimate of total costs at contract completion by performing corroborating inquiries with the Company’s project managers and personnel involved with the contracts, and comparing the estimates to management’s [removed: workplans,] [added: work plans,] suppliers’ contracts, subcontract agreements, third-party invoices from suppliers, historical actual results, and/or engineering specifications. |

| | ◾ | Evaluating changes in estimates of total costs at [removed: contract] [added: project] completion by obtaining evidence regarding timing and amounts supporting these changes in estimates such as approved change order documents, communications with the customer, subcontract agreements and related amendments, and recent actual costs. |

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

| [removed: Cash and cash equivalents] [added: CASH AND CASH EQUIVALENTS, beginning of period] | ​ | [removed: $] | 205,150 | ​ | [removed: $] | 57,214 | ​ | [added: | 58,776 | ​ |]

| Billed accounts receivable, less allowance for credit losses of [removed: $11,926] [added: $15,286] and [removed: $10,640,] [added: $11,926,] respectively | ​ | | [removed: 1,318,926] [added: 1,861,212] | ​ | | [removed: 1,024,082] [added: 1,318,926] | ​ |

| Unbilled accounts receivable, less allowance for credit losses of [removed: $850] [added: $1,475] and [removed: $1,011,] [added: $850,] respectively | ​ | | [removed: 72,774] [added: 95,786] | ​ | | [removed: 77,030] [added: 72,774] | ​ |

| Other receivables, less allowance for credit losses of [removed: $522] [added: $553] and [removed: $510,] [added: $522,] respectively | ​ | | [removed: 166,319] [added: 86,186] | ​ | | [removed: 38,369] [added: 166,319] | ​ |

| Inventories | ​ | | [removed: 65,538] [added: 59,224] | ​ | | [removed: 35,309] [added: 65,538] | ​ |

| Prepaid expenses and other | ​ | | [removed: 54,309] [added: 46,213] | ​ | | [removed: 48,456] [added: 54,309] | ​ |

| Costs and estimated earnings in excess of billings, less allowance for credit losses of [removed: $79] [added: $271] and [removed: $80,] [added: $79,] respectively | ​ | | [removed: 28,084] [added: 91,681] | ​ | | [removed: 27,211] [added: 28,084] | ​ |

| Total current assets | ​ | | [removed: 1,911,100] [added: 2,790,241] | ​ | | [removed: 1,307,671] [added: 1,911,100] | ​ |

| PROPERTY AND EQUIPMENT, NET | ​ | | [removed: 208,568] [added: 277,180] | ​ | | [removed: 143,949] [added: 208,568] | ​ |

| LEASE RIGHT-OF-USE ASSET | ​ | ​ | [removed: 205,712] [added: 229,106] | ​ | ​ | [removed: 130,666] [added: 205,712] | ​ |

| GOODWILL | ​ | | [removed: 666,834] [added: 875,270] | ​ | | [removed: 611,789] [added: 666,834] | ​ |

| IDENTIFIABLE INTANGIBLE ASSETS, NET | ​ | | [removed: 280,397] [added: 434,417] | ​ | | [removed: 273,901] [added: 280,397] | ​ |

| DEFERRED TAX ASSETS | ​ | ​ | [removed: 17,723] [added: 85,441] | ​ | ​ | [removed: 115,665] [added: 17,723] | ​ |

| OTHER NONCURRENT ASSETS | ​ | | [removed: 15,245] [added: 19,433] | ​ | | [removed: 13,837] [added: 15,245] | ​ |

| Total assets | ​ | $ | [removed: 3,305,579] [added: 4,711,088] | ​ | $ | [removed: 2,597,478] [added: 3,305,579] | ​ |

| Current maturities of long-term debt | ​ | $ | [removed: 4,867] [added: 6,042] | ​ | $ | [removed: 9,000] [added: 4,867] | ​ |

| Accounts payable | ​ | | [removed: 419,962] [added: 654,943] | ​ | | [removed: 337,385] [added: 419,962] | ​ |

| Accrued compensation and benefits | ​ | | [removed: 169,136] [added: 228,622] | ​ | | [removed: 127,765] [added: 169,136] | ​ |

| Billings in excess of costs and estimated earnings and deferred revenue | ​ | | [removed: 909,538] [added: 1,149,257] | ​ | | [removed: 548,293] [added: 909,538] | ​ |

| Accrued self-insurance | ​ | | [removed: 27,774] [added: 42,315] | ​ | | [removed: 27,644] [added: 27,774] | ​ |

| Other current liabilities | ​ | | [removed: 189,928] [added: 501,591] | ​ | | [removed: 120,715] [added: 189,928] | ​ |

| Total current liabilities | ​ | | [removed: 1,721,205] [added: 2,582,770] | ​ | | [removed: 1,170,802] [added: 1,721,205] | ​ |

| LONG-TERM DEBT | ​ | | [removed: 39,345] [added: 62,293] | ​ | | [removed: 247,245] [added: 39,345] | ​ |

| LEASE LIABILITIES | ​ | | [removed: 188,136] [added: 212,107] | ​ | | [removed: 111,744] [added: 188,136] | ​ |

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

| OTHER LONG-TERM LIABILITIES | ​ | | [removed: 77,944] [added: 147,017] | ​ | | [removed: 67,764] [added: 77,944] | ​ |

| Total liabilities | ​ | | [removed: 2,027,750] [added: 3,006,412] | ​ | | [removed: 1,597,555] [added: 2,027,750] | ​ |

| Treasury stock, at cost, [removed: 5,438,625] [added: 5,562,453] and [removed: 5,362,224] [added: 5,438,625] shares, respectively | ​ | | [removed: (209,807)] [added: (273,799)] | ​ | | [removed: (187,212)] [added: (209,807)] | ​ |

| Additional paid-in capital | ​ | | [removed: 339,562] [added: 350,734] | ​ | | [removed: 332,080] [added: 339,562] | ​ |

February 20, 2025

| ​ | | 2024 | | | 2023 | | ​ |

| Cash and cash equivalents | ​ | $ | 549,939 | ​ | $ | 205,150 | ​ |

| Net income | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 522,433 | ​ | ​ | 522,433 | ​ |

| Issuance of shares for options exercised | ​ | — | ​ | ​ | — | ​ | 5,369 | ​ | ​ | 248 | ​ | ​ | (64) | ​ | ​ | — | ​ | ​ | 184 | ​ |

| Issuance of restricted stock & performance stock | ​ | — | ​ | ​ | — | ​ | 74,129 | ​ | ​ | 2,982 | ​ | ​ | 2,371 | ​ | ​ | — | ​ | ​ | 5,353 | ​ |

| Share repurchase | ​ | — | ​ | ​ | — | ​ | (177,158) | ​ | ​ | (58,307) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (58,307) | ​ |

| BALANCE AT DECEMBER 31, 2024 | ​ | 41,123,365 | ​ | $ | 411 | ​ | (5,562,453) | ​ | $ | (273,799) | ​ | $ | 350,734 | ​ | $ | 1,627,330 | ​ | $ | 1,704,676 | ​ |

| Proceeds from other debt | ​ | ​ | 640 | ​ | ​ | — | ​ | ​ | — | ​ |

December 31, 2024

We adopted this standard beginning with our 2024

annual reporting and applied the requirements of the standard retrospectively to all periods presented.

There was no impact of adoption on our consolidated financial position, results of operations or cash flow, but our disclosure in Note 16, “Segment Information” has been updated to conform with the requirements of ASU 2023-07.

In November 2024, the FASB issued ASU 2024-03, “Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses.” The standard requires entities to disclose, on an annual and interim basis, disaggregated information about certain income statement expense line items in the notes to the financial statements.

These items are expected to be billed and collected in the normal course of business.

Other unbilled receivables where payment is subject to factors beyond just the passage of time are included in contract assets.

with a corresponding receivable from our insurance carrier.

We do

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

| Total | ​ | ​ | $ | 7,027,476 | ​ | 100.0 | % | ​ | $ | 5,206,760 | ​ | 100.0 | % | ​ | $ | 4,140,364 | ​ | 100.0 | % |

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

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

| Total | ​ | ​ | $ | 7,027,476 | ​ | 100.0 | % | ​ | $ | 5,206,760 | ​ | 100.0 | % | ​ | $ | 4,140,364 | ​ | 100.0 | % |

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.

| Cash and cash equivalents | ​ | $ | 549,939 | ​ | $ | — | ​ | $ | — | ​ | $ | 549,939 |

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

Summit Industrial Construction, LLC Acquisition

As a result of the acquisition, Summit is a wholly owned subsidiary of the Company reported in our mechanical segment.

Revenue attributable to Summit was $420.1 million for the eleven months from the acquisition date.

The following summarizes the acquisition date fair value of consideration transferred and the acquisition date fair value of the identifiable assets acquired and liabilities assumed, including an amount for goodwill (in thousands):

| ​ | ​ | ​ |

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

| Consideration transferred: | ​ | ​ |

| Cash paid at closing | $ | 267,500 |

| Working capital adjustment | ​ | 14,602 |

| Notes issued to former owners | ​ | 35,000 |

| Estimated fair value of contingent earn-out payments | ​ | 42,732 |

| ​ | $ | 359,834 |

​

Such revisions are

February 22, 2024

| BALANCE AT DECEMBER 31, 2020 | | 41,123,365 | ​ | $ | 411 | | (4,935,186) | ​ | $ | (129,243) | ​ | $ | 322,451 | ​ | $ | 502,810 | | $ | 696,429 | ​ |

| Net income | | — | ​ | | — | | — | ​ | | — | ​ | | — | ​ | | 143,348 | | | 143,348 | ​ |

| Issuance of shares for options exercised | | — | ​ | | — | | 195,724 | ​ | | 5,399 | ​ | | 235 | ​ | | — | | | 5,634 | ​ |

| Issuance of restricted stock & performance stock | | — | ​ | | — | | 101,360 | ​ | | 2,681 | ​ | | (473) | ​ | | — | | | 2,208 | ​ |

| Share repurchase | | — | ​ | | — | | (362,796) | ​ | | (27,054) | ​ | | — | ​ | | — | | | (27,054) | ​ |

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

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

| CASH AND CASH EQUIVALENTS, beginning of period | ​ | | 57,214 | ​ | | 58,776 | ​ | | 54,896 | ​ |

In October 2021, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2021-08, “Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers.” This standard requires an acquirer to apply Accounting Standards Codification Topic 606 to recognize and measure contract assets and contract liabilities in a business combination.

ASU 2021-08 is effective for

We adopted this standard on January 1, 2023, and the impact on our consolidated financial statements was not material.

been impaired involve market-based information.

Loss estimates associated with the larger and

invoiced to the customer at any point during the contract.

services underlying each performance obligation.

the changes on current and prior periods based on our progress towards complete satisfaction of a performance obligation.

Contract assets are not

The increase in contract assets was primarily due to an increase of $4.1 million as a result of the acquisitions of Eldeco, Inc. (“Eldeco”) and DECCO, Inc. (“DECCO”).

This increase was substantially offset by a decrease of $3.2 million due to the timing of billings and related costs and estimated earnings in excess of billings at December 31, 2023 as compared to December 31, 2022.

Additionally, there was an increase of $12.1 million as a result of the Eldeco and DECCO acquisitions.

In April 2020, we entered into interest rate swap agreements to reduce our exposure to variable interest rates on our revolving credit facility.

The interest rate swap agreements terminated on September 30, 2022.

recognized a net gain of $0.3 million and a net loss of $0.5 million, respectively, related to our interest rate swaps.

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

| Life insurance—cash surrender value | ​ | $ | — | ​ | $ | 9,315 | ​ | $ | — | ​ | $ | 9,315 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |

On April 1, 2022, we acquired Atlantic Electric, LLC and its related subsidiary (“Atlantic”), headquartered in Charleston, South Carolina, and with operations in South Carolina and Western North Carolina, for a total purchase price of $48.1 million, which included $34.1 million of cash paid on the closing date, $5.3 million in notes payable to former owners and a working capital adjustment.

Atlantic performs electrical contracting for customers in various South Carolina markets, as well as installation of airport runway lighting in the Southeast.

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

| Balance at December 31, 2021 | ​ | $ | 361,320 | ​ | $ | 230,794 | ​ | $ | 592,114 | ​ |

| Customer Relationships | | 6.4 | ​ | $ | 376,621 | ​ | $ | (193,338) | ​ | $ | 340,721 | ​ | $ | (161,049) |

| Backlog | | 0.6 | ​ | | 5,900 | ​ | | (4,331) | ​ | | 3,200 | ​ | | (2,361) |

| Total | ​ | ​ | ​ | $ | 512,182 | ​ | $ | (231,785) | ​ | $ | 465,482 | ​ | $ | (191,581) |

backlog period.

| 2024 | ​ | $ | 39,851 | ​ |

| 2025 | ​ | | 36,095 | ​ |

| 2026 | ​ | | 35,251 | ​ |

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: 2023] [added: 2024] 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: 2023] [added: 2024] 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: 2023.][added: 2024.]

Due to the recent nature of these business combinations, [removed: Eldeco] [added: Summit, J&S] and [removed: DECCO’s] [added: Precision’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: 2023.][added: 2024.]

As such, our management has excluded [removed: Eldeco] [added: Summit, J&S] and [removed: DECCO] [added: Precision] from its assessment of the effectiveness of internal control over financial reporting as of December 31, [removed: 2023.][added: 2024.]

Collectively, [removed: Eldeco] [added: Summit, J&S] and [removed: DECCO] [added: Precision] comprised [removed: 5.2%] [added: 12.6%] of total assets and [removed: 2.5%] [added: 9.0%] of revenues in our consolidated financial statements as of and for the year ended December 31, [removed: 2023.][added: 2024.]

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: 2023.][added: 2024.]

We have audited the internal control over financial reporting of Comfort Systems USA, [removed: Inc.] [added: Inc] and [removed: its consolidated] subsidiaries (the “Company”) as of December 31, [removed: 2023,] [added: 2024,] 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: 2023,] [added: 2024,] 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 [added: as] of [removed: the Company] [added: and] for the year ended December 31, [removed: 2023,] [added: 2024,] and our report dated February [removed: 22, 2024,] [added: 20, 2025,] expressed an unqualified opinion on those [removed: consolidated] 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: Eldeco,] [added: J&S Mechanical Contractors,] Inc. [added: (“J&S”)] (acquired February 1, [removed: 2023)] [added: 2024), Summit Industrial Construction, LLC (“Summit”) (acquired February 1, 2024),] and [removed: DECCO, Inc.] [added: Precision Plumbing and Service, LLC (“Precision”)] (acquired [removed: October 2, 2023),] [added: May 1, 2024)] and whose financial statements collectively constitute [removed: 5.2%] [added: 12.6%] of total assets and [removed: 2.5%] [added: 9.0%] of total revenues in the consolidated financial statement amounts as of and for the year ended December 31, [removed: 2023.][added: 2024.]

Accordingly, our audit did not include the internal control over financial reporting at [removed: Eldeco, Inc.] [added: J&S, Summit,] and [removed: DECCO, Inc.][added: Precision.]

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 over Financial Reporting.][added: Control.]

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

The Company acquired Eldeco, Inc. in February 2023 and DECCO, Inc. in October 2023.

​

February 22, 2024

During the three months ended December 31, [removed: 2023,] [added: 2024,] 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: 2024] [added: 2025] (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: 2024] [added: 2025] (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.

We have an insider trading policy which governs the purchase, sale, and/or other dispositions of its securities (and related derivative securities) by the Company, directors, officers and key employees and other covered persons and is designed to promote compliance with insider trading laws, rules and regulations, and listing standards applicable to the Company.

A copy of the Company’s Insider Trading Window Policy is filed as Exhibit 19 to this Annual Report on Form 10-K.

| *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 | ​ | | [removed: Filed Herewith] [added: 2023 Form 10-K] |

| 21.1 | ​ | | [List of subsidiaries of Comfort Systems USA, [removed: Inc.](https://www.sec.gov/Archives/edgar/data/1035983/000155837024001529/fix-20231231xex21d1.htm)] [added: Inc.](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex21d1.htm)] | ​ | ​ | ​ | | Filed Herewith |

| 23.1 | ​ | | [Consent of Deloitte & Touche [removed: LLP](https://www.sec.gov/Archives/edgar/data/1035983/000155837024001529/fix-20231231xex23d1.htm)] [added: LLP](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex23d1.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/1035983/000155837024001529/fix-20231231xex31d1.htm)] [added: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex31d1.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/1035983/000155837024001529/fix-20231231xex31d2.htm)] [added: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex31d2.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/1035983/000155837024001529/fix-20231231xex32d1.htm)] [added: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex32d1.htm)] | ​ | ​ | ​ | | Furnished Herewith |

| 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/1035983/000155837024001529/fix-20231231xex32d2.htm)] [added: 2002](https://www.sec.gov/Archives/edgar/data/1035983/000155837025001222/fix-20241231xex32d2.htm)] | ​ | ​ | ​ | | Furnished Herewith |

| 97 | ​ | | [Comfort Systems USA, Inc. Policy for Recoupment of Incentive Compensation](https://www.sec.gov/Archives/edgar/data/1035983/000155837024001529/fix-20231231xex97.htm) | ​ | ​ | ​ | | [removed: Filed Herewith] [added: 2023 Form 10-K] |

| Date: February [removed: 22, 2024] [added: 20, 2025] | ​ | ​ |

| /s/ Brian E. Lane | ​ | President, Chief Executive Officer, and | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ William George | ​ | Executive Vice President and Chief Financial | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ Julie S. Shaeff | ​ | Senior Vice President and Chief Accounting | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ Franklin Myers | ​ | [removed: Chairman] [added: Chair] of the Board | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ Darcy G. Anderson | ​ | Director | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ Herman E. Bulls | ​ | Director | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ RHOMAN J. HARDY | ​ | Director | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ Pablo G. Mercado | ​ | Director | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ William J. Sandbrook | ​ | Director | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ Constance E. Skidmore | ​ | Director | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ Vance W. Tang | ​ | Director | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

| /s/ Cindy L. Wallis-Lage | ​ | Director | ​ | February [removed: 22, 2024] [added: 20, 2025] | ​ |

​

​

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

| /s/ Gaurav Kapoor | ​ | Director | ​ | February 20, 2025 | ​ |

| Gaurav Kapoor | ​ | ​ | ​ | ​ | ​ |

| ​ | ​ | ​ | ​ | ​ | ​ |