Backlogs, Not Chips: FIX, EME and STRL Ride AI Build-Out

Comfort Systems USA (NYSE: FIX), EMCOR Group (NYSE: EME) and Sterling Infrastructure (NASDAQ: STRL) are seeing expanding backlogs as AI data-center spending flows into electrical, cooling and site work, with FIX trading at $1,605.53, EME at $754.73 and STRL at $514.27 as of 15:19 GMT on Sept. 22, 2026.

The scarce input in artificial intelligence is starting to look less like silicon and more like a licensed electrician with an open calendar. Three publicly traded contractors — Comfort Systems USA (NYSE: FIX), EMCOR Group (NYSE: EME) and Sterling Infrastructure (NASDAQ: STRL) — sit at the point where AI capital spending stops being a press release and becomes conduit, chillers, switchgear and graded dirt. All three are reporting expanding backlogs, and the composition of that backlog is the tell: money is moving into electrical work, cooling systems and site preparation.

That framing was laid out by Nasdaq Markets, which compared the three companies on growth and diversification. The investment question it raises is narrower than "is AI real": it is which of these three is most levered to the build-out, and what happens to each if the build-out slows.

Where the three stocks trade right now

As of the last trade at 15:19 GMT on Sept. 22, 2026, with the market open:

Comfort Systems USA (FIX) — $1,605.53, down 1.66% on the day from a prior close of $1,632.59, with an intraday range of $1,596.31 to $1,633.50. That is a decline of roughly $27 per share on the session.
EMCOR Group (EME) — $754.73, down 0.39% from a prior close of $757.71, trading between $752.54 and $762.30.
Sterling Infrastructure (STRL) — $514.27, up 0.32% from a prior close of $512.64, with the widest relative swing of the three: $503.00 to $519.16.

The backdrop is a split tape. The S&P 500, via SPY, is effectively flat at $773.49 against a $773.50 prior close. The Nasdaq 100 tracker QQQ is up 0.48% at $745.02. The Dow proxy DIA is down 0.48% at $517.28. So on a day when large-cap technology is bid and industrial-heavy indices are soft, two of the three AI-adjacent contractors are trading with the Dow rather than with the chipmakers — a reminder that these are still cyclical construction businesses in the eyes of the market, whatever their end customer builds.

Why backlog is the number that matters

For a specialty contractor, backlog is contracted work not yet performed. It is the closest thing the sector has to a forward order book, and it is why investors in FIX, EME and STRL watch it the way semiconductor investors watch bookings. A rising backlog means revenue is already spoken for; it also means pricing power, because a contractor with a full schedule can be selective about which jobs it takes and at what margin.

The AI-specific point is the mix inside that backlog. Electrical work and cooling are the two disciplines a hyperscale data center cannot do without and cannot easily defer. A building shell can be value-engineered. Megawatts of power distribution, redundant switchgear and the mechanical plant that keeps dense GPU racks from cooking themselves cannot. Site work — grading, earthmoving, utilities, pads — comes first in sequence, which makes it an early indicator: the dirt moves before the transformers arrive, and the transformers arrive before the servers.

That sequencing is worth holding onto when reading these three names. A site-work-weighted business sees the cycle earlier. A mechanical and electrical business sees it in the middle. Commissioning and service revenue arrive last and tend to persist after construction ends.

Three different ways to own the same theme

The three are not interchangeable. The comparison the source draws is explicitly about growth versus diversification, and that is the right axis.

Comfort Systems USA

Comfort Systems is the mechanical and electrical contractor of the group — HVAC and plumbing at its core, with electrical capability layered on. Cooling is not an ancillary line item in a modern data center; it is a primary engineering constraint. FIX is also the most expensive of the three on a headline share price at $1,605.53, and today it is the weakest performer, off 1.66%. It closed near the bottom of its intraday range, which is the kind of tape action that follows profit-taking in a crowded trade rather than any change in the underlying order book.

EMCOR Group

EMCOR is the diversification case. It is a large electrical and mechanical construction and facilities-services operation with exposure well beyond data centers — commercial buildings, healthcare, industrial, institutional work, plus a recurring maintenance and service arm. That breadth cuts both ways. It dilutes the pure AI-capex beta that some investors want, and it is exactly what cushions results if hyperscaler spending plans get trimmed. At $754.73, EME is nearly unchanged on the session, down 0.39%, and its intraday range is the tightest of the three.

Sterling Infrastructure

Sterling is the site-work and heavy civil name — the earthmoving, paving and infrastructure end of the chain, with e-infrastructure work tied directly to data-center and large-warehouse pads. It is the only one of the three higher today, up 0.32% to $514.27, and it traded across a $16 band from $503.00 to $519.16. That volatility is characteristic: Sterling is the smallest-priced of the trio and the most directly tied to project starts, which makes it the highest-beta expression of the theme.

The risk hiding inside a full order book

Backlog growth is not the same as earnings growth. Three things can separate them. Labor is the first: skilled electricians and pipefitters are the actual bottleneck, and wage inflation on a fixed-price contract lands squarely on the contractor. Second is concentration. Work awarded by a handful of hyperscale customers is high-quality revenue until one of them pauses a campus, at which point the customer list looks uncomfortably short. Third is timing. Site work leads, mechanical and electrical follow, commissioning trails — so a slowdown in project starts shows up in Sterling's numbers before it shows up in EMCOR's service revenue.

There is also the power question that sits above all three. Data-center projects are increasingly gated by grid interconnection and transformer lead times, not by a contractor's capacity. A backlog can be real and still convert slowly if the utility cannot energize the site.

What to watch from here

The next set of quarterly reports is where the thesis gets tested, and the useful disclosures are specific: the direction and duration of backlog, how much of it is data-center or "e-infrastructure" work, gross margin on new awards versus work being burned off, and any commentary on labor availability. Investors should also watch whether the three continue to trade as a basket. Today they did not — Sterling up, Comfort Systems down more than a percent, EMCOR barely moved — which suggests the market is beginning to price the differences between site work, mechanical systems and diversified facilities services rather than treating all three as a single AI derivative.

For now the structural point stands. Compute demand has to land somewhere physical, and the people who pour the slab, pull the wire and hang the chillers get paid before the first token is generated.

Key facts

Comfort Systems USA (NYSE: FIX): $1,605.53, -1.66%, as of 15:19 GMT Sept. 22, 2026
EMCOR Group (NYSE: EME): $754.73, -0.39%, as of 15:19 GMT Sept. 22, 2026
Sterling Infrastructure (NASDAQ: STRL): $514.27, +0.32%, as of 15:19 GMT Sept. 22, 2026
Shared driver: Expanding backlogs in electrical, cooling and site work tied to AI build-out

Frequently asked questions

Which three contractors are tied to the AI build-out?

Comfort Systems USA (NYSE: FIX), EMCOR Group (NYSE: EME) and Sterling Infrastructure (NASDAQ: STRL). All three are reported to be benefiting from the physical construction behind artificial intelligence, with expanding backlogs reflecting spending on electrical systems, cooling and site preparation work for data centers and related facilities.

What does 'backlog' mean for a construction contractor?

Backlog is contracted work that has been awarded but not yet performed. It functions as a forward order book: a growing backlog means future revenue is already committed, and it typically gives the contractor more leverage on pricing because a full schedule lets management be selective about which projects to accept.

How did the three stocks trade on Sept. 22, 2026?

As of the last trade at 15:19 GMT, Comfort Systems USA was at $1,605.53, down 1.66% from a $1,632.59 prior close. EMCOR Group was at $754.73, down 0.39%. Sterling Infrastructure was the only gainer, up 0.32% at $514.27 after ranging between $503.00 and $519.16.

Why is electrical and cooling work the bottleneck rather than chips?

Dense AI computing racks require large amounts of power distribution and heat removal. Switchgear, redundant electrical systems and mechanical cooling plant cannot be deferred or simplified the way other building elements can, and the skilled trades that install them are in limited supply, making that labor and capacity the binding constraint.

How do the three companies differ from one another?

Comfort Systems is weighted toward mechanical and electrical work, including HVAC. EMCOR is the most diversified, combining electrical and mechanical construction with facilities services across many end markets. Sterling Infrastructure is the site-work and heavy civil name, tied closely to project starts and earthmoving ahead of vertical construction.

What are the main risks to this trade?

Skilled labor shortages and wage inflation can compress margins on fixed-price contracts. Customer concentration among a few hyperscale buyers means a single paused campus can dent awards. Grid interconnection and transformer lead times can also slow how quickly a reported backlog converts into recognized revenue.

Sources

AI's Physical Bottleneck Isn't Chips. It's These Contractors. — Nasdaq Markets