Comfort Systems USA, a mechanical and electrical services contractor, has seen its stock surge 77% this year and 871% over three years, driven by its role in AI data centre construction. The company's backlog has grown to $14.06 billion, exceeding projected 2026 revenue of $13 billion. Technology-related revenue, including data centres, now represents 58% of total revenue, up from 40% the previous year. President Trent McKenna noted this substantial increase during a July earnings call. The company's backlog reflects contracted installation and replacement project work, typically lasting under one year. It excludes service work and maintenance contracts, meaning the figures don't fully capture long-term revenue opportunities. The backlog continues expanding as hyperscalers invest heavily in AI infrastructure.

US Treasury yields near 4.79% reflect strong corporate borrowing for AI investments rather than economic weakness, according to analysts Joel Litman and Rob Spivey. They argue that context matters more than absolute rate levels. Companies borrowing at 5% to fund projects returning 30-40% benefit from current rates, whilst those earning less than borrowing costs face pressure. The analysts note that AI-related corporate debt issuance reached roughly $1.5 trillion this year, driving yields higher. Alphabet posted its first negative free cash flow since 2004, burning $5.9 billion in Q2 as capital expenditure hit $44.9 billion. Amazon swung to negative $7.6 billion on a trailing basis. However, negative cash flow can signal productive investment rather than distress, the analysts suggest.

Comfort Systems USA stock has fallen more than 20% from its all-time high, despite strong fundamentals in the AI infrastructure sector. The company provides HVAC, plumbing, piping, and electrical systems for data centers, with demand expected to rise as AI data center construction accelerates. The US currently has over 3,000 operational data centers, with more than 1,500 under construction. Fortune Business Insights projects AI data centers will grow at a 25.8% compound annual growth rate through 2034. Comfort Systems USA reported $3.27 billion in second-quarter revenue, up 51% year-over-year. The company generates income both from initial construction and ongoing maintenance of data centers. Whilst construction represents the bulk of current revenue, maintenance income should increase as more facilities come online, creating steady long-term revenue streams.