Comfort Systems backlog surges 81% to $12.5B on data center boom

The artificial intelligence boom is fueling a gold rush for more than just microchips, driving a historic buildout of physical data centers that has pushed the order book for Comfort Systems USA Inc. (NYSE: FIX) to a record $12.45 billion.

That backlog, an 80.8% increase from the $6.89 billion reported a year prior, shows how intense the demand for specialized electrical and mechanical systems has become. In its first-quarter 2026 earnings call, the company attributed the growth to a surge in hyperscale data center and modular infrastructure projects, reinforcing the idea that the AI trade extends deep into the industrial sector.

The growth is not limited to Comfort Systems. Sterling Infrastructure Inc. (NASDAQ: STRL), which prepares data center sites, reported a $3.8 billion backlog, while Quanta Services Inc. (NYSE: PWR), which connects facilities to the power grid, holds a massive $48.5 billion backlog. The figures underscore the massive capital investment required to build the foundation for AI, from site preparation to grid connection to the intricate HVAC systems needed to cool high-performance processors.

For investors, the results confirm that companies providing the "picks and shovels" of the AI revolution are in a period of exceptional growth. The key question now is how long the tech-driven spending spree can last and how much of that future growth is already reflected in stock prices that have seen triple-digit gains.

The AI Infrastructure Stack

Investors often focus on chip designers like Nvidia, but a trio of infrastructure companies highlights the less-visible supply chain required to make AI possible. Each firm addresses a critical chokepoint in data center construction, and all three reported strong first-quarter 2026 earnings beats and raised their full-year guidance.

Sterling Infrastructure (STRL): The company does the foundational work, preparing the physical sites where data centers are built. Its E-Infrastructure segment saw a 174% acceleration in the first quarter, with management raising full-year revenue guidance by 20%.
Quanta Services (PWR): As a contractor for electrical infrastructure, Quanta connects the new data centers to the power grid. The company raised its full-year guidance to over $35 billion after a strong first quarter, supported by its $48.5 billion backlog.
Comfort Systems USA (FIX): Inside the building, Comfort Systems designs and installs the complex mechanical, electrical, and plumbing systems. Its specialty is HVAC for data centers, where precise cooling is critical for servers running AI workloads.

Record Growth Meets Execution Risk

While the demand is undeniable, the rapid expansion is not without challenges. Sterling's management noted that a primary headwind is finding enough qualified electricians and project managers to keep up with demand, forcing the company to be more selective when bidding for jobs.

For Comfort Systems, the growth is highly concentrated in the hyperscale tech customer segment. While this has powered its recent success, it also presents a risk if those customers were to suddenly pull back on spending. Some analysts note this concentration as a key concern, even as they project continued revenue growth.

The market has rewarded these companies handsomely for their position in the AI buildout. FIX shares are up more than 300% in the last 12 months, while STRL stock has gained more than 170% year-to-date. While technical indicators for FIX and PWR remain bullish, the rapid ascent and overbought signals for STRL suggest investors may need to be selective as valuations climb.

This article is for informational purposes only and does not constitute investment advice.