Comfort Systems USA, Inc. FIX

Key data

The business

Comfort Systems USA installs and services the mechanical and electrical systems inside commercial buildings: the HVAC, chilled-water plants, piping and wiring. Mechanical is 71% of revenue, electrical 29%. What has changed the company is the customer. Technology, meaning data centers and chip plants, is now 58% of revenue, up from a broad base of hospitals, schools and factories a few years ago. Modular is 17% of the mix: instead of sending electricians into a field, the company builds climate systems as finished modules in its own plants and ships them to site, faster and at a higher margin. The moat is unglamorous and real: forty-odd local operating companies that own the customer relationships, and access to licensed crews in a business that cannot hire fast enough. In a labor-starved business, having the people who can pour a mechanical room is the edge. What the customer signs is a fixed-price contract for a pre-built cooling plant, delivered in weeks a competitor cannot match.

The numbers

Five straight quarters of accelerating growth, and the rate of change is the story.

Revenue grew 50% year over year in Q2 and profit 91%, because margins widen as volume climbs. The company has beaten the analyst number by 15% to 55% in each of the last four quarters, so the Street is chasing a business it keeps underestimating. The reading obligation of the sector is the operating leverage, and it is holding.

Every incremental dollar of revenue this quarter dropped about 24 cents of operating profit, above the 17% corporate average, which is what a mix shift into modular looks like when it is working rather than a cyclical peak. The five-year record is a compounding machine: revenue roughly tripled from $3.1B in 2021 to about $9.1B in 2025, near 31% a year, while EPS went from $3.93 to $28.88, more than seven-fold.

Consensus has FY2026 EPS at $49.01, up 70% on last year, then $60.18 in 2027, a step down to 23% growth. What this memo believes that the multiple does not: with $14.1 billion of remaining performance obligations and incremental margins holding near 24%, the modular step is structural, not a peak, and the forward earnings are more visible than a "cyclical contractor at 30 times EBITDA" fear allows. The print that settles it is incremental operating margin staying above 20% while backlog still grows.

Management

CEO Brian Lane sold $186.3M of stock across 33 sales in the last twelve months, with zero purchases, the three largest being $25.8M in August, $21.9M in May and $13.6M in February 2026. Plan status is not disclosed in the feed, so whether these are scheduled 10b5-1 sales into a tripled share price or discretionary calls cannot be split here, and that ambiguity matters at this multiple. The capital record is cleaner: over 2007 to 2025 the company put 71% of deployed capital into acquisitions and only 18% into buybacks, and the roll-up of local contractors is how it grew. Returns are exceptional, ROE 53.6% and ROIC 38.8%, on a net-cash balance sheet of $1.85B in cash against $54M of long-term debt.

How it fails or surprises you

Technology concentration. With 58% of revenue tied to data centers and chip plants, a single hyperscaler pause in 2026 or 2027 hits the order book hard and fast. Watch the technology share of quarterly bookings; a two-quarter decline in that line is the first sign the theme is cooling, well before revenue rolls over.

Backlog that does not convert. The $14.1B RPO is firm orders, not cash, and the risk the company names first is cancellation or delay. The tell is billings in excess of costs, now $3.23B; if that balance flattens while backlog still reads high, the work has stopped starting.

Margins keep climbing (right tail). If modular scales further and incremental margins hold above 24%, FY2027 EPS clears the $60 consensus and the stock re-rates on earnings the Street modeled too low. The print: operating margin through 18% on the next two quarters.

Closing thoughts

A specific print resolves this one, so name it: the incremental operating margin and the direction of technology bookings over the next two quarters. Hold above 20% incrementals with backlog still growing, and the earnings power the market is paying 30 times EBITDA for is real and durable, and the buyer at today's price is right that this is a structural compounder, not a contractor at a cycle top. Flatten the incrementals or shrink the tech line, and the multiple has no floor to stand on, because the entire premium rests on the data-center build continuing. The left tail, a hyperscaler CapEx pause landing on a 58%-concentrated book priced for perfection, is the one that takes out years of gains, and it is fatter than the price implies. The right tail is a clean beat past $60 in 2027.

The bet is still that America keeps building data centers, and that Comfort Systems keeps winning the job of putting the cooling, piping and electrical guts inside them. It breaks the day the technology customers stop signing, and the pair to watch is the technology share of bookings against the $14.1B backlog, quarter by quarter. If that backlog stops growing while incremental margins slip below 20%, the story is over regardless of what the last print looked like.