Few businesses are benefiting as much from the artificial intelligence (AI) infrastructure boom as Comfort Systems USA (FIX +1.70%). The company ended 2025 with a backlog of $12 billion. For perspective, the backlog was at $6 billion at the end of 2024.
Comfort Systems provides critical contractor services for data centers, which is why its backlog is growing so fast. This is undoubtedly why Wall Street is increasingly looking at the stock.
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Many institutional investment managers are required to file a 13F when buying or selling stocks. According to 13f.info, there were nearly 1,100 13F filings for Comfort Systems in the fourth quarter alone. For perspective, only 700 13F filings were made in the fourth quarter of 2024, showing a massive surge in trading activity by the so-called "smart money."
Here's why smart money is piling into Comfort Systems stock.
NYSE: FIX
Key Data Points
Strong results from this smooth operator
Comfort Systems installs and maintains mechanical, electrical, and plumbing (MEP) systems. The business is booming thanks to demand from data centers, but its services are useful in many commercial buildings.
Over the last several years, Comfort Systems' revenue has soared. And this incredible increase in demand has helped to boost its operating margin to an all-time high.
FIX Revenue (TTM) data by YCharts
Comfort Systems isn't only enjoying strong profit margins because of the high demand for its services. It's also getting more profitable thanks to its business model. The company prefabricates what it can in its own facilities before installing it on site. This controlled environment allows it to do more efficient work.
Scaling this modular capacity is a key component of Comfort Systems' profitable growth. At the end of 2025, management announced it would increase its modular capacity by about 30% in 2026. This will help it service its fast-growing backlog of work.
You don't need to be "smart money" to like this
To be clear, Comfort Systems was growing before AI catalyzed demand in data centers. The company continues to acquire small MEP players around the country to keep growth going. And management is making investments to deliver strong profitability for years to come.
Smart money or not, investors should like this situation. Comfort Systems is a business that doesn't go out of style -- buildings need their cooling, heating, and plumbing systems regularly serviced after they're installed. And old systems need updating. Even if new construction slows, Comfort Systems still has work to do.
Moreover, Comfort Systems has built its business for strong profit margins. And its large backlog gives relative confidence that growth hasn't peaked yet. This is why smart money continues to pile into Comfort Systems USA stock. And it's why shareholders of this industrial stock have enjoyed an incredible 2,200% gain over the last five years.
