Comfort Systems USA (FIX) Q3 2026: Backlog Jumps $3.75 Billion

Comfort Systems USA (FIX) reported third-quarter 2026 results on October 22, 2026, in its earnings release and Form 10-Q for the quarter ended September 30, and the Comfort Systems USA Q3 2026 backlog jumped by $3.75 billion in a single quarter [1][2]. The filing shows data center orders still accelerating and cash flow still running well ahead of profit, while gross margin eased for the quarter.

Going into the report, three questions mattered. Could backlog convert quickly during the peak construction season without shrinking? Was gross margin leaning too heavily on upward estimate revisions from older projects? And could cash flow, supported by customer prepayments, stay above net income while the company buys modular factory space? Backlog and revenue came in clearly above the earlier baselines, and cash flow was confirmed. Gross margin stayed above the downside line but missed the confirmation level. Taken together, growth and cash generation strengthened, profit conversion held steady, and the operating model is unchanged, though its scale and investment intensity have stepped up.

Comfort Systems USA is a large US mechanical and electrical contractor. Its 52 operating units install HVAC, process piping, electrical and controls systems in many types of buildings, and the company prefabricates modular components for data centers in its own plants [2]. About 94.7% of revenue comes from bid installation projects, mostly under fixed-price contracts. In the third quarter, technology customers, mainly data centers, supplied 60.8% of revenue [2].

Backlog rose $3.75 billion in one quarter

Backlog grew much faster than earlier expectations. Backlog reached $17.81 billion on September 30, up $3.75 billion from $14.06 billion at June 30 and up 90.0% from a year earlier. Same-store backlog rose $3.67 billion, led by four operations: Texas electrical, the large Texas modular operation, a Virginia operation and a Texas mechanical operation [2][3]. Because backlog rose sharply even after a peak construction quarter, new contracts signed in the quarter far exceeded the work completed.

Revenue conversion also beat the earlier baseline. Third-quarter revenue was $3.77 billion, up 15.3% from $3.27 billion in the second quarter and up 53.7% from a year earlier; same-store revenue grew 46.3% [1][2]. Technology-sector revenue was $2.29 billion, roughly double the prior-year level [2]. Management raised full-year same-store growth guidance from the "mid-to-high 30%" range given in July to the "mid-40%" range and gave a 2027 revenue growth outlook in the "mid-20%" range [4][5]. Management said the constraint on growth is craft labor rather than demand [4]. The company expects to recognize about 65-75% of backlog within 12 months, but the increase is highly concentrated, so delays on a few projects would affect the conversion pace [2].

Customer prepayments kept lifting cash flow

Cash from customer prepayments did not reverse in the third quarter. Operating cash flow was $1.01 billion, 2.1 times net income of $489.0 million. The 10-Q attributes most of the year-over-year increase in nine-month operating cash flow to more net advance payments [1][2]. Contract liabilities, meaning billings in excess of costs plus deferred revenue, rose from $3.23 billion at June 30 to $3.87 billion [2][6]. In the first nine months the company recognized $1.75 billion of revenue from contract liabilities held at the start of the year, which shows new prepayments from large projects are arriving faster than old ones are consumed [2].

Modular expansion stayed within the plan of capital spending at about 5% of revenue. Nine-month capital expenditures were $499.4 million, or 5.05% of revenue, mainly for building purchases in the mechanical segment [1][2][5]. Management reiterated that modular capacity will exceed 4 million square feet by the end of 2026 and plans about 6 million square feet by the end of 2027, with capacity allocated first to customers with five-year volume commitments [4]. If new orders slow, the consumption of prepayments would push operating cash flow below net income.

Gross margin eased, with less help from estimate revisions

Gross margin returned to the prior-year level, and profit relied less on upward estimate revisions on older projects. Third-quarter gross margin was 24.8%, down from 25.9% in the second quarter and flat with the prior-year quarter. Revenue from changes in estimates fell to 4.5% of revenue from 7.7% [2][7]. Mechanical segment gross margin was about 25.1%, above the prior-year quarter, while electrical margin was about 24.3%, below 26.2% a year earlier [2][4]. Management attributed the decline to early material deliveries on early-stage jobs and called the effect temporary, an explanation that still needs to be verified [4]. SG&A fell from 9.4% to 8.3% of revenue, which kept operating margin at 16.6% [1][2].

Conclusion

The quarter strengthened the case on growth and cash generation, while profit conversion held steady. The large backlog increase and guidance that now extends into 2027 lengthen revenue visibility, and prepayments lifted operating cash flow to about twice net income. The main uncertainties are order concentration, craft labor supply and whether margins on early-stage projects recover; the earnings call information comes from a structured summary rather than a verbatim transcript. In the next annual report, the key evidence will be whether backlog keeps growing, whether gross margin returns above 25%, and whether contract liabilities begin to decline.

Sources

[1] FIX 8-K filed 2026-10-22 · 3Q26 results press release (2026-10-22, Comfort Systems USA Form 8-K Exhibit 99.1, https://www.sec.gov/Archives/edgar/data/1035983/000110465926118156/fix-ex99d1.htm) [2] FIX 10-Q filed 2026-10-22 · 3Q26 (2026-10-22, Comfort Systems USA Form 10-Q, https://www.sec.gov/Archives/edgar/data/1035983/000110465926118159/fix-20260930x10q.htm) [3] FIX 10-Q filed 2026-07-23 · backlog June 30, 2026 and bookings by operation (2026-07-23, Comfort Systems USA Form 10-Q, https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0001035983&type=10-Q&dateb=&owner=include&count=40) [4] FIX 3Q26 earnings call 2026-10-23 · Drillr structured summary (2026-10-23, Drillr structured earnings call summary) [5] FIX 2Q26 earnings call 2026-07-24 · Drillr structured summary · full-year 2026 guidance (2026-07-24, Drillr structured earnings call summary, https://ir.comfortsystemsusa.com/) [6] FIX 10-Q filed 2026-07-23 · contract assets and liabilities June 30, 2026 (2026-07-23, Comfort Systems USA Form 10-Q, https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0001035983&type=10-Q&dateb=&owner=include&count=40) [7] FIX 10-Q filed 2026-07-23 · 2Q26 gross profit (2026-07-23, Comfort Systems USA Form 10-Q, https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0001035983&type=10-Q&dateb=&owner=include&count=40)