Quotes for the same replacement job can spread widely, and a cheap bid that skips the permit, the load calculation, or the panel assessment is a red flag regardless of the dollar figure. The spread usually isn’t about brand or equipment — it’s about what each bid did and didn’t include.
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That’s the pattern this checklist is built for. The contractor who gives you a good answer to each question below is describing more work, not charging more for the same work. The one who can’t answer them is describing less.
Use the sections below for the job type you’re dealing with.
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For any HVAC job (ask these first)
1. “Are you licensed and insured in this state, and can I see the documentation?”
Good answer: license number is on the proposal, or they pull it up immediately. They name the carrier for liability and workers’ comp.
Bad answer: “of course we are” with no documentation produced. A contractor who is licensed has the number memorized. One who isn’t, deflects.
Why it matters: if an unlicensed tech is injured at your home, or the work causes property damage, your homeowner’s insurance may not cover it.
2. “Is a permit required for this job, and are you pulling it?”
Good answer: yes, a permit is required (most replacement and new-installation work requires one), and they’re pulling it as part of the scope. The permit cost should appear as a line item.
Bad answer: “we can skip the permit and save you money” or “permits aren’t really required for this.” Unpermitted work can fail to pass inspection, void the equipment warranty, and complicate a home sale.
3. “What’s the warranty on your labor, in writing?”
Good answer: a specific term (“we warrant our labor for one year” or “two years”) written into the proposal.
Bad answer: “we stand behind our work.” That’s a philosophy, not a warranty. Without a written term, you have nothing to enforce if the installation causes a failure at month 13.
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📊 Deciding whether to repair or replace?
Compare your own quotes with BidSmart, a bid-comparison tool from our team. Upload the quotes you’ve received and see how they stack up line-by-line — scope, equipment tiers, and the items a low bid quietly leaves out — before you sign anything.
For system replacement
4. “Did you perform a Manual J load calculation, and can I see it?”
Good answer: yes, here’s the output: a room-by-room heat gain and heat loss calculation based on your home’s square footage, insulation, window area, and local climate data.
Bad answer: “we sized it off the old unit” or “we use 500 square feet per ton.” Sizing off the old unit locks in any existing mismatch. An oversized system short-cycles and leaves the house humid; an undersized one runs constantly and can’t keep up on the hottest days.
5. “What’s included in the scope: lineset, electrical, permit, pad, ductwork modifications?”
Good answer: each item listed as its own line with a cost or a “included.” You should be able to see whether the lineset is being replaced or reused, whether a new concrete pad is included, whether any electrical upgrade is in scope.
Bad answer: one blended price with no itemization. The 44% spread in the bids above lived almost entirely in this question. The cheapest bid excluded the permit, the lineset replacement, and the panel assessment that every honest contractor included.
6. “What model numbers are you quoting: outdoor unit, indoor coil, and controls?”
Good answer: full model numbers in writing for all three components. An AHRI-matched combination of outdoor unit and indoor coil is required for the rated efficiency to apply.
Bad answer: “a 3-ton Trane” or “a 16 SEER2 Carrier.” Without model numbers, you can’t verify that the bids are comparing the same tier of equipment, and you have no basis for checking the efficiency rating.
7. “What refrigerant type does this system use, and does my current lineset need to be replaced?”
Good answer: explains that newer R-454B or R-32 systems may require different line set materials, and tells you whether your existing lineset passes or needs replacement. This is a legitimate scope difference that honest bids surface and dishonest bids quietly ignore.
Bad answer: a blank stare, or “it should be fine.” Reusing a lineset that isn’t compatible contaminates the refrigerant charge and voids the equipment warranty.
8. “Will you verify refrigerant charge at startup, not just connect a gauge?”
Good answer: yes, we’ll check superheat on fixed-orifice systems or subcooling on TXV systems at commissioning and document the readings.
Bad answer: “we’ll add refrigerant if it needs it.” Adding refrigerant without a measurement is guessing. Overcharge and undercharge both reduce efficiency and shorten compressor life.
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For compressor replacement
9. “Have you ruled out the capacitor and contactor before calling the compressor gone?”
Good answer: yes. The tech replaced the capacitor, checked the contactor for voltage drop and pitting, and then ran a megohm (insulation resistance) test and an amp-draw test on the compressor with the new capacitor in place.
Bad answer: “the compressor is gone.” A failed capacitor causes a healthy compressor to hum and stall, a presentation that can look definitive on a diagnostic tablet but isn’t. The capacitor is a $150 repair. A compressor is $800–$2,300. Insist on the capacitor swap before condemning the compressor.
10. “Is this compressor in warranty? Can you check the serial number?”
Good answer: the tech looks it up on the spot. Compressor warranties on registered equipment typically run 5–10 years; a compressor replaced under warranty costs labor only, not the $500–$800 part. Contractors who don’t check are leaving money on the table: yours or theirs.
Bad answer: “your unit is old” without checking. Age is not a warranty determination. Serial number is.
11. “If another component fails within a year of the compressor replacement, what’s the policy?”
Good answer: a clear explanation of what their labor warranty covers on the compressor job specifically, and what constitutes a related vs. unrelated failure.
Bad answer: “we can’t know that.” That’s true of any future failure — but a contractor who declines to discuss it doesn’t want accountability for work adjacent to theirs.
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For ductwork work
12. “Will you do a duct leakage test before and after the work?”
Good answer: yes. A duct blaster or blower door test before and after gives you a number (what percentage of conditioned air you’re losing to leakage) and confirms the work actually reduced it.
Bad answer: “we’ll just seal what we can see.” Visual sealing alone frequently misses the leaks that matter most: small gaps in inaccessible sections of trunk line, boot connections at hard-to-reach registers. A before/after test proves the work worked.
13. “Is Aeroseal in scope, or manual mastic and tape sealing?”
Good answer: explains both options honestly. Manual sealing with mastic compound and foil tape is appropriate for accessible, visible leaks. Aeroseal (pressurized sealant injected through the duct system) reaches leaks in inaccessible sections and is backed by pre/post leakage tests. Price difference is real: manual sealing runs $400–$1,900; Aeroseal runs $1,300–$3,000.
Bad answer: “we’ll seal it up” with no distinction between methods and no mention of what percentage of leakage the approach typically seals.
14. “Will replacement ductwork be insulated to current code?”
Good answer: yes, and they specify the R-value (R-6 for most attic duct runs in hotter climates; your local code may specify otherwise).
Bad answer: “it’ll be fine.” Uninsulated or under-insulated duct in unconditioned space is a major efficiency drain and a code violation in most jurisdictions.
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For tune-ups
15. “What’s on your tune-up checklist, and can you leave me a copy afterward?”
Good answer: 12–18 specific items: contactor, capacitor, coil, amp draw, refrigerant check, condensate, thermostat calibration, flue inspection for a furnace visit. A written report left behind.
Bad answer: “we do a complete inspection.” Any contractor who can’t name five items on their checklist without hesitation isn’t running a checklist.
16. “If you find something wrong, will you tell me before doing any repair, with the cost in writing?”
Good answer: yes, every time.
Bad answer: “we’ll take care of it.” You should approve every repair in writing before it happens. “We’ll take care of it” is how a $130 tune-up becomes a $700 invoice you didn’t see coming.
17. “Do you check refrigerant charge, and what’s your method?”
Good answer: yes: superheat measurement on on fixed-orifice systems, subcooling on TXV systems, using calibrated gauges. A tune-up is the right time to catch a slow refrigerant leak before it causes a compressor failure.
Bad answer: “we feel the line” or “we’ll add a can if it needs it.” Feeling the suction line is not a refrigerant diagnosis. Adding refrigerant without measuring is guessing.
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How to use this list
You don’t need to ask all 17 questions on every call. The universal questions (1–3) apply to every job. Then pick the section for your job type and ask 4–6 questions that are specific to it.
The point isn’t to interrogate contractors. It’s to find the ones who can answer these without hesitation — because they already do this work. Those are the quotes worth comparing. The ones who dodge or talk around the questions are telling you what their bid will and won’t include.
For a breakdown of what each of these job types actually costs, see HVAC Repair and Replacement Costs.
Still deciding whether to replace at all? Start one step earlier with the new-system decision guide, then bring the bids back here.
Once the bids are in, how to hire an HVAC company covers the license/insurance checks and quote red flags this list doesn’t, before you sign anything.
For a refrigerant quote specifically, there is a tool that breaks it into line items and compares each one.
