The compressor has failed, the unit is fifteen years old and the contractor says replacement is the sensible choice. Within a day you have three quotes. One is for a unit with the same capacity as the old one, one recommends a different size and one includes a higher efficiency model, a new thermostat and a curb adapter. The prices differ by thousands of dollars and each salesperson is sure that theirs is the right answer.
Replacement quotes are difficult to compare because they describe different solutions to the same problem. This guide explains what drives the differences: sizing, efficiency ratings, scope of work and the items that quotes commonly leave out. It also shows how to ask for quotes that can be compared and how to spot the questions that tell you the most.
In brief
- Ask whether a load calculation was done and ask to see it.
- Efficiency ratings pay back faster where the unit runs long hours.
- Crane, curb adapter, permit and disposal lines can quietly add to the price.
- Compare model numbers, warranties and scope, not only totals.
In this guide
Replacement is a design decision
Replacing equipment is often treated as a swap, but it is an opportunity to correct earlier mistakes. Many buildings have been renovated since the original installation. Insulation may have improved, lighting may have changed to LED, windows may have been replaced and occupancy may differ. The old unit may have been oversized from the start, a common situation, or may no longer suit the load.
A good contractor treats replacement as a chance to confirm what the building really needs.
Sizing: the heart of the quote
HVAC capacity is typically expressed in tons of cooling, where one ton is 12,000 BTU per hour, and in BTU for heating. Choosing the right size requires a load calculation, a systematic estimate of how much heat the building gains or loses based on its area, construction, insulation, windows, orientation, occupancy and equipment. A standard method is published by industry bodies, and many contractors use software to apply it.
The shortcut is a rule of thumb, such as a ton per several hundred square feet, or simply matching the nameplate on the old unit. That can work by coincidence. It can also produce problems:
- cools the space quickly and then shuts off. It short-cycles, doesn’t remove humidity well, runs unevenly and wears out sooner.
- runs constantly and still cannot keep up on peak days.
Ask each contractor: “Did you perform a load calculation, and can I see it?” If the answer is “we always replace like with like,” ask what changed since the original installation.
Efficiency ratings
Equipment efficiency is described by standardized ratings. You will often see:
- for cooling efficiency over a season.
- for efficiency at a specific hot operating condition.
- for heat pump heating efficiency.
- for gas furnace efficiency.
- for some commercial equipment.
Higher numbers mean better efficiency, and equipment with higher ratings generally costs more. Whether the extra cost pays back depends on how many hours the unit runs, local electricity and gas prices, climate and incentives. In a building that runs the system all day in a hot climate, a more efficient unit can pay back sooner than in a part-time seasonal shop.
Ask the contractor to estimate operating cost differences between options using your utility rates, and to state their assumptions. We do not give financial advice, and we cannot promise any specific savings.
Refrigerants and rules
Refrigerants used in HVAC equipment are regulated, and the rules change as older refrigerants are phased down in favor of alternatives. Replacement equipment today uses refrigerants that differ from those in older units. This matters in two ways. First, old equipment may be costly to repair if it uses a refrigerant that is being phased out. Second, you cannot simply swap a new compressor into an old system designed for a different refrigerant. Ask the contractor what refrigerant the new equipment uses and what that means for service. Handling refrigerant is regulated and must be done by certified technicians.
The scope checklist
- Equipment — Make, model, capacity, efficiency rating.
- Sizing basis — Load calculation or other justification.
- Curb and ductwork — New curb adapter, duct modifications, sealing.
- Electrical — Disconnects, wiring, breaker changes if needed.
- Controls — Thermostat or building controls.
- Crane or rigging — Equipment lift for rooftop units.
- Permits — Who pulls and pays.
- Disposal — Removal of the old unit and refrigerant recovery.
- Startup and commissioning — Testing and airflow verification.
- Warranty — Equipment and labor, in years.
- Timeline — Lead time for equipment and installation.
Items such as crane charges, curb adapters and permits can add significant cost. A quote that omits them is not necessarily lower; the cost will appear later.
Comparing quotes fairly
- Ask each contractor to quote the same capacity or to justify a different one.
- Prices vary by brand and series; a model number lets you check specifications.
- Mark each as included, excluded or not applicable.
- Equipment warranties from the manufacturer are separate from labor warranties from the contractor.
- Equipment availability varies and can delay a project.
- Verify credentials with the relevant licensing board.
Be wary of high-pressure tactics, such as “this price is only good today.” Reputable contractors are generally willing to wait a few days for you to decide, particularly when the system is not in complete failure.
Repair or replace
When a system is older, a major repair can raise the question. A rule of thumb used by some technicians multiplies the age of the system by the repair cost and compares the result with replacement cost. It is a rough guide, not a law. Consider:
- The age and condition of the equipment.
- The cost of repair compared with replacement.
- Whether replacement parts are available.
- The refrigerant type and its future cost.
- The expected remaining time in the building.
- Energy savings from newer equipment.
Our guide to commercial maintenance contracts explains how regular service can postpone replacement decisions, and our comparison of system types can help you decide whether to replace like-for-like or change approach.
Financing, incentives and leases
Replacement may be financed through the contractor, a lender or an equipment lease. Compare total cost, not just the monthly payment. Utility rebates and tax incentives may be available for efficient equipment, but eligibility and amounts change. We do not give tax or financial advice. Ask your utility, program administrators and an accountant what applies to you, and get the details in writing before you sign.
If you lease your space, check your lease before replacing equipment. The landlord may be responsible, or may require approval for changes.
Questions to ask
- Did you perform a load calculation? Can I see it?
- Why did you choose this capacity and efficiency?
- What refrigerant does the new unit use?
- What is included in the price, and what is excluded?
- Who handles permits and inspections?
- How is the old unit removed and its refrigerant recovered?
- What are the equipment and labor warranties?
- How long will the building be without cooling or heating?
The short version
A good replacement quote shows its reasoning: a load calculation, a named model, a complete scope and clear warranties. Compare quotes on scope and sizing, not just price. Ask what has been left out, and take enough time to make a decision, even in a hurry. For ongoing savings after the new unit is in, see our guide to thermostats and schedules.
What to do next
- Gather your last twelve months of utility bills and a description of any renovations.
- Ask at least two contractors to perform a load calculation.
- Request quotes with named models and itemized scope.
- Ask what refrigerant the equipment uses and what it means for service.
- Check licenses and insurance with the relevant agencies.
- Take a few days to decide unless the system has completely failed.
