Commercial HVAC replacement and installation in Kent.

Most commercial buildings run packaged rooftop units, and federal research puts that equipment over nearly half of all U.S. commercial floor space. That makes the decision fairly standard: you are choosing among three paths, not twenty. The old unit's fuel type, the building's heating load, and the electrical service you already have narrow it quickly. Price at least two of the three. The cheapest install is rarely the cheapest decade, and the highest-efficiency option is not automatically right for a building that runs limited hours or has no room left in its panel. Ask every bidder to hold tonnage and airflow constant across the options so the numbers actually compare. Where the fuel choice is genuinely open, compare installed cost plus modeled utility impact, not the equipment sticker alone.

No one can price a commercial rooftop replacement from a tonnage number alone. These are the lines that separate a clean swap from a project. Make each bidder show them separately so you can see where the money actually goes.

DOE's rooftop replacement guidance names the pattern most buildings fall into: managers wait until the unit stops conditioning the space, needs constant service, or quits entirely. That wait is expensive twice. The old unit burns money the whole time — federal estimates put the waste from aging, inefficient rooftop units at $900 to $3,700 per unit each year — and the emergency call narrows your choice to whatever is available that week.

The same guidance makes the more useful point. Replacing proactively with a more efficient unit often beats both replacement-on-failure and a like-for-like swap at the end of service life. You pick the efficiency tier, the fuel path, and the crane date, and you fold the curb and controls work in while the roof is already open. Doing it on a planned date also means the tenants below get notice instead of a surprise.

So the question is not only what a new unit costs. It is what the current one costs you to keep, what it will cost to replace on a bad day in August, and what the building actually needs from the unit that follows it.

Two buildings can get very different numbers for the same tonnage. The gap is almost always access and infrastructure, not equipment. Here is what pushes a job toward each end.

A quote that arrives without anyone on the roof is a guess wearing a number. The review that makes it real is short, and it settles the same handful of questions every time.

First, the load. The nameplate on a twenty-year-old unit reflects the building as it was, not as it is. Occupancy, plug load, lighting, and envelope work all shift the answer, and carrying the old tonnage forward carries any original sizing error forward with it.

Second, infrastructure. DOE's heat pump guidance flags three items specifically: electrical capacity, physical constraints, and gas lines. Those decide whether an all-electric option is even on the table, before efficiency or price enters the conversation.

Third, the roof itself. Curb dimensions, structural capacity, and where a crane can actually reach set the rigging plan and a real share of the cost.

Fourth, contractor availability. The same guidance calls out installer familiarity with the technology as a live constraint. Newer equipment is only as good as the startup behind it. None of this takes long. It just has to happen before the number, not after it.

The crane day is one morning of noise. What you actually buy is a decade or more of operating behavior, and two decisions shape it more than the equipment brand does. Neither one shows up until a comfort complaint in month two, and both are far easier to settle before the purchase order than after the unit is in the air. If the building has more than one rooftop unit, treat these as fleet decisions rather than one-off ones. The second and third replacements move faster when the first one sets the standard.

If you own several rooftop units, replacing them one emergency at a time is the most expensive way through. DOE's Advanced RTU Campaign is the scale version of the same idea: more than 200 organizations upgraded over 43,000 units and now save a combined $37 million a year on energy bills. Owners in that campaign either replaced old units with more efficient ones or retrofitted advanced controls, whichever made better financial sense per unit.

That is a useful frame even for a small portfolio. Rank your units by age, service history, and the space each one serves. Replace the worst first, on a planned date, and let that job set the template — efficiency tier, controls approach, curb adapter detail. The units that follow price faster and install cleaner.

Procurement belongs in the same conversation. Equipment availability is a real constraint, and DOE lists it alongside electrical capacity and contractor knowledge when judging whether a technology fits a site. A unit selected early, with lead time confirmed in writing, is a scheduled project. The same unit selected the day yours fails is whatever the supply house happens to have.

Two quotes for the same roof should be readable side by side. When they are not, it is usually because one of these five items is buried inside a lump sum. Ask for each as its own line.