AI chip maker Nvidia has dominated the stock market conversation over the past five years. But it isn't the S&P 500's best performer. That distinction belongs to Comfort Systems, an HVAC and plumbing contractor that has seen its share jump more than 2,000%.

Comfort Systems is a classic hard-hat company, employing about 18,000 workers including plumbers, pipe fitters, welders and other skilled technicians to install and maintain heating and cooling systems, plumbing and more at factories and other industrial sites.

It's been a huge beneficiary of the AI picks-and-shovels boom, with its data-center revenue exploding over the past several years. Its hands-on business model means it's continued to thrive in recent weeks, as investors grow wary of many tech and software stocks.

Comfort Systems stock has posted five-year average annual returns of more than 87%, the highest in the S&P 500, according to Bespoke Investing Group. That's led to a cumulative return of more than 2,100%. Nvidia, by contrast, has retuned 66% a year. What's more, Comfort Systems is up 46% year to date in 2026, while Nvidia is essentially flat.

Comfort Systems earnings per share more than tripled between 2021 and 2024, according to FactSet. Wall Street will get the latest read on its financials after the market closes Thursday. Wall Street analysts forecast a fourth-quarter profit of $6.75 a share on sales of $2.3 billion. The forecast suggests earnings growth of about 66% on the $4.09 the company earned in the final quarter of 2024.

With its stock price rallying so sharply, Comfort Systems may not have a lot of room for error. The stock's forward price-to-earning ratio has jumped to nearly 43 from 23 just 12 months ago.

That said, investors may want to look for buy-the-dip moments.

"Investors should treat periodic pullbacks as opportunities," wrote William Blair analyst Tim Mulrooney earlier this month. He added that unlike some more direct AI plays, electrical and plumbing companies, such as Comfort Systems and rival Emcor Group, stand to benefit from a number of business trends, such as reshoring and shortages of skilled workers.

Mulrooney rates Comfort Systems as Outperform -- although it's worth noting that, with shares trading at $1,350 Thursday afternoon, they had already blown through his Feb. 5 target price of $1,230.

In the long run, Comfort Systems has plenty of room to grow. While the market is still sussing how the AI revolution will play out, few doubt that the U.S. will need additional data centers, which also cater to AI-adjacent fields like cloud-computing.

With roughly $10 billion in annual revenue, the company has expanded in part by acquiring local operators in the highly fragmented HVAC and plumbing industries. While Comfort Systems has 184 U.S. locations, it remains concentrated in the Southeast, with comparatively few operations in Texas and almost none west of the Rockies.

The company spent an average of $93 million a year on acquisitions between 2007 and 2024, according to a recent presentation, that amounted to about three-fourths of its excess cash, with the rest going to buy backs and dividends.