How to vet a contractor and compare bids

1. The bid, not the brand

Homeowners shop equipment brands. The install quality matters more than the brand on the box: a well-sized, well-commissioned mid-tier system beats a premium unit installed badly, every time. So the goal of vetting isn't to find the cheapest number or the biggest name — it's to find the contractor whose scope of work is complete and correct and whose price reflects it. Get at least three written bids; one quote tells you nothing about whether it's fair.

2. Before you call

Walk in with your own numbers and the right scope, so you're comparing bids on the same job rather than being sold three different ones:

• Run a planning estimate first (the relevant calculator on this site) so you know roughly what the work should cost in your state before anyone quotes you. A bid 2–3× the planning range deserves a hard question.
• Insist on a load calculation, not a rule of thumb. For HVAC, that is an ACCA Manual J load calculation followed by Manual S equipment selection (and Manual D when ducts are being designed). For an existing electrical service, ask which NEC dwelling-load method the electrician used; the applicable section can vary by adopted NEC edition and project. Oversizing is a common and expensive mistake, and "we'll match what you have" is not a calculation.
• Write down the scope yourself in one paragraph (e.g., "replace 3-ton AC + gas furnace with a cold-climate heat pump, keep furnace as dual-fuel backup, include any panel work"). Hand the same paragraph to every bidder.

3. The three non-negotiables (verify, don't take their word)

• License. Confirm any license required by your state or locality and trade using the issuing agency's lookup. Licensing rules vary. Unlicensed work can create permit, warranty, financing, resale, or insurance problems; check the equipment warranty and your policy rather than assuming a universal consequence.
• Insurance. Ask for current proof of general liability and workers' compensation coverage where required, and verify the certificate with the listed agent or carrier. Coverage and homeowner liability rules vary by state.
• Permit. Confirm with the local building department whether the job requires a permit, who will pull it, and who schedules inspection. Where a permit is required, it should appear in the written scope. Skipping required permits removes an independent code check and can complicate resale or later corrective work.

4. Questions that reveal a good contractor

For HVAC:

• "Will you do a Manual J load calculation, and can I have a copy?" (A good contractor says yes without flinching.)
• "What's the cold-climate rating — the HSPF2 and the capacity at my design temperature?" (Tests whether they spec for your climate or just grab a unit.)
• "Are you recommending dual-fuel or a backup, and why?" (Reveals whether they've thought about your coldest days.)
• "Which refrigerant does this model use, and are the installers trained and equipped for that manufacturer's A2L installation requirements?"

For electrical:

• "Which NEC dwelling-load method did you run, and does my existing service actually need upgrading — or would listed load-management equipment work?" (A panel upgrade you don't need is a common upsell.)
• "Are the service-entrance conductors copper or aluminum, and is the meter base included?"
• "Who coordinates with the utility for the disconnect/reconnect, and is that fee in the bid?"

5. How to read and compare bids

A real bid is itemized. Beware the single-line "$X for a heat pump" quote — you have no way to compare it. A complete bid breaks out:

• Equipment (make, model, size/tonnage, efficiency rating)
• Labor and any subcontracted electrical work
• Ancillaries: line sets, condensate handling, ductwork repair, pads/mounts, electrical circuit or panel work
• Permit + inspection fee, and utility coordination fee where applicable
• Removal/disposal of old equipment, and any drywall/finish repair
• Warranty terms — both the manufacturer's parts warranty and the contractor's labor warranty

When three bids differ a lot, the difference is almost always in the scope, not the markup — a low bid that omitted the panel work or the ductwork isn't cheaper, it's incomplete. Normalize the bids to the same scope before you compare the totals.

6. What a fair price looks like

It is normal and legitimate for an installed price to be well above the equipment's retail box price — you're paying for sizing, labor, code compliance, permits, warranty, and a company that will still exist when something needs service. A useful sanity check is the planning range from the calculator: a bid within or modestly above the low/mid/high band for your state is reasonable; a bid far below it usually means missing scope (or an unlicensed/uninsured operator), and a bid far above it deserves an itemized explanation. The planning range is a guardrail, not a target — your home's specifics legitimately move the number.

7. Red flags that should end the conversation

• "We can skip the permit to save you money."
• Pressure tactics and "today only" pricing on a multi-thousand-dollar install.
• A large deposit demanded up front (a deposit for special-order equipment is normal; paying most of the job before work starts is not).
• No written, itemized scope — or refusal to provide a load calculation.
• Cash-only, no license number on the contract, or no proof of insurance.
• "You definitely need a panel upgrade" with no load calculation to back it up.
• Sizing by rule of thumb ("a ton per 500 square feet") instead of a Manual J.

8. After you sign and after the install

• Get it in writing: the itemized scope, the equipment models, the price, the timeline, the warranty, and that the permit is included.
• Don't pay in full until the inspection passes. Hold a final payment until the permit is closed out by the local inspector.
• Commissioning matters: for HVAC, ask that refrigerant charge and airflow be measured and recorded, not eyeballed — an undercharged or airflow-starved system quietly loses much of the efficiency you paid for.
• Register the equipment for the full manufacturer warranty, and keep the permit and invoice with your home records — the next buyer's inspector will ask.