Key Highlights

● Comfort Systems fell after hours on October 22 despite the strong quarter.

● Revenue of $3.77 billion beat the $3.39 billion expected.

● Earnings of $13.91 a share compared with $8.25 a year earlier.

● Backlog climbed to $17.81 billion from $14.06 billion at June 30.

Comfort Systems USA (NYSE:FIX) fell after the bell on Thursday, October 22, 2026, despite reporting third-quarter results that showed sharp growth in revenue and profit. The stock, listed on the NYSE Composite, declined in after-hours trading, with sources reporting drops of differing sizes.

The stock had already slid during the regular session along with other companies tied to AI and data center construction.

A blowout quarter

Comfort Systems reported third-quarter revenue of $3.77 billion, well above the $3.39 billion analysts had expected, according to market data. That compared with $2.45 billion a year earlier, meaning revenue rose by roughly half.

Earnings grew even faster. The company reported earnings of $13.91 per share, up from $8.25 a year earlier, according to its filing with the Securities and Exchange Commission. In the filing, CEO Brian Lane highlighted the sharp jumps in both revenue and per-share earnings.

The company's backlog, which measures work that has been contracted but not yet completed, climbed to $17.81 billion from $14.06 billion at the end of June. A rising backlog suggests demand for Comfort Systems' services remains strong.

Why the stock fell anyway

Comfort Systems installs and services mechanical and electrical systems, including heating, ventilation and air conditioning, plumbing and electrical work, in commercial and industrial buildings. Data centers have become one of its fastest-growing markets, which made it a favorite among investors betting on the AI build-out.

That popularity can cut both ways. Stocks that have rallied strongly often carry high expectations, and even very good results can trigger selling if investors were positioned for more or decide to take profits.

Thursday's market mood also worked against the company. Investors were pulling back from AI infrastructure after Meta Platforms (NASDAQ:META) reported heavy spending and its first cash outflow in more than a decade, according to market data.

GE Vernova (NYSE:GEV) was among the weakest performers in the S&P 500, while Quanta Services (NYSE:PWR), Vertiv (NYSE:VRT) and Eaton (NYSE:ETN) fell sharply. MasTec (NYSE:MTZ), Dycom (NYSE:DY) and Primoris (NYSE:PRIM) hit 52-week lows. Bloom Energy (NYSE:BE), another AI power name, also fell after the bell despite beating forecasts.

The regular session

The Nasdaq Composite fell 694.00 points to 26,008.86, its steepest drop since June 5, and the S&P 500 lost 93.74 points to 7,663.43, its worst day since July. The S&P 500 industrials sector slipped, weighed down by AI power names.

But the market was healthier beneath the surface. About two of every three S&P 500 stocks rose, according to market reports, and the Dow Jones Industrial Average edged up 11.89 points to 52,867.98.

Treasuries rallied strongly as investors sought safety, and the 10-year yield closed back below a closely watched threshold for the first time since September 22.

Comfort Systems Faces Friday's Open and Demand Questions

The first test is whether the after-hours decline holds when regular trading resumes on Friday, October 23.

Investors will look for management commentary on data center demand, project margins and how the backlog will convert into revenue in 2027. Big Tech spending plans will also matter: Microsoft (NASDAQ:MSFT) and Alphabet (NASDAQ:GOOGL) report on Wednesday, October 28, and Amazon (NASDAQ:AMZN) reports on October 29, offering fresh signals on whether the data center construction boom continues.