Cost figures are broad editorial ranges. A written local quote and an on-site load calculation should replace them before you buy.
01Normalize the equipment first
- Outdoor unit, indoor coil, air handler, furnace, and thermostat model numbers.
- Nominal capacity and the capacity available at relevant design conditions.
- SEER2, EER2, HSPF2, AFUE, stages, and variable-capacity features that actually differ.
- AHRI certificate or manufacturer-rated matched-system documentation.
- Included accessories: heat strips, filter cabinet, humidifier, surge protection, line-hide, pad, stand, or controls.
02Compare the design, not just the boxes
ENERGY STAR recommends right-sizing from the home’s characteristics instead of a rule of thumb. Ask which Manual J inputs were used, how Manual S informed equipment selection, and whether ducts and return-air capacity were evaluated. An old nameplate or square-foot shortcut is not a substitute for a documented load.
If bidders recommend different sizes, ask each to explain the design temperatures, envelope assumptions, occupancy, ventilation, and safety margin. The goal is not to force identical equipment; it is to understand why the recommendations differ.
03Build one scope-comparison table
| Comparison line | Bid A | Bid B | Bid C |
|---|---|---|---|
| Manual J / sizing basis | Record method | Record method | Record method |
| Exact matched equipment | Models + AHRI | Models + AHRI | Models + AHRI |
| Duct and airflow corrections | Included / excluded | Included / excluded | Included / excluded |
| Electrical, permit, disposal | Included / excluded | Included / excluded | Included / excluded |
| Commissioning deliverables | List tests | List tests | List tests |
| Labor and parts warranty | Years + exclusions | Years + exclusions | Years + exclusions |
| Cash price / financed total | Both totals | Both totals | Both totals |
04Read warranties and financing as contracts
Separate manufacturer parts coverage from the contractor’s labor warranty. Record registration deadlines, maintenance requirements, transfer rules, diagnostic charges, refrigerant coverage, travel fees, and who performs warranty work. A long headline warranty can still leave meaningful ownership costs uncovered.
For financing, compare cash price, amount financed, annual percentage rate, term, promotional expiration, deferred-interest rules, fees, monthly payment, and total of payments. A lower monthly payment can represent a higher project cost.
05Define acceptance before work begins
- Permit and inspection responsibility.
- Airflow or static-pressure measurement and required corrections.
- Refrigerant charging method and startup documentation.
- Drainage, overflow protection, controls, staging, and backup-heat configuration.
- Owner training, manuals, model/serial records, warranty registration, and final cleanup.
- Change-order approval process and payment milestones.
A bid becomes easier to trust when the contractor is willing to define what ‘finished and operating correctly’ means before installation day.
06A defensible final decision
Choose the proposal that best fits the documented load, corrects known building or airflow problems, defines commissioning, offers serviceable equipment, and prices the complete scope transparently. Reputation, licensing, insurance, references, communication, and local parts support belong in the decision alongside the equipment.
If one total is dramatically lower, identify the missing scope before treating it as savings. If one is dramatically higher, identify which measurable outcome, risk reduction, or warranty supports the premium.
—Sources & verification
We link to primary or responsible sources so you can check current requirements before acting.
This guide is educational. Do not open electrical or refrigerant compartments, bypass safety controls, or handle refrigerant. Use qualified, properly licensed professionals where required.