A new HVAC system is a five-figure purchase that will live with your house for 12-20 years. Most homeowners spend more time researching a $1,200 mattress than they spend evaluating their HVAC contract. Here are the five questions I tell my mom to ask any installer she's considering. They sort the honest contractors from the not-so-honest ones in about ten minutes.
1. “Did you do a Manual J load calculation?”
Manual J is the industry-standard residential heat-loss/heat-gain calculation. It accounts for square footage, insulation, window area, sun orientation, occupancy, and local climate to determine the actual cooling and heating load of your home. It's how a competent installer determines what size system to put in.
If the answer is “we use square footage” or “the existing system is 4 tons so we'll match that,” walk away. The existing system is probably oversized (most are), and matching it just compounds the problem.
The right answer is something like: “Yes, we'll do a Manual J on-site. It takes about 30 minutes during the estimate visit. Here's a sample of what one looks like.”
2. “Are you replacing the line set?”
The refrigerant line set runs from your indoor evaporator to your outdoor condenser. When you swap from R-22 to R-410A or R-454B (any new system since 2010), you should replace the line set. Why? Old R-22 systems used mineral oil; new systems use POE oil; mineral-oil residue contaminates POE oil and can foul the new compressor.
Lazy installers leave the old line set and just “flush” it. The flush is rarely complete. Then your $9,000 new system runs contaminated for 8 years and dies of a sludge-related compressor failure.
Right answer: “Yes, we replace the line set on every install. If we're not changing refrigerant types, we still inspect for kinks and replace if we see issues.”
Wrong answer: “We can flush the old one to save you money.” That's $400 saved upfront and a $5,000 compressor failure in year 8.
3. “Are you pulling a permit?”
HVAC installation requires a permit in every California city I work in. Period. The permit:
- Triggers a city building-department inspection that verifies the work was done to code
- Protects your home insurance — claims for a fire or CO incident on unpermitted work can be denied
- Becomes part of your home's records, which matters at sale
A “cash deal, no permit” installer is asking you to take all the legal and insurance risk while they pocket a couple hundred bucks. Hard pass. The permit is $150-$400 in most South Bay cities; refusing to pull one is a red flag for everything else they're cutting corners on.
4. “What's the warranty — in writing — on parts AND labor?”
The manufacturer's parts warranty is automatic on a registered system (typically 10 years on parts, 10-12 on the compressor). The labor warranty is the installer's commitment, and it's where companies cut corners.
Industry-standard labor warranty is 1 year minimum, 2 years preferred. Anything less is a sign the installer doesn't expect to be in business in 2 years.
Also ask:
- Will you register the equipment with the manufacturer for me? (Most won't unless asked, and unregistered = warranty drops to 5 years.)
- What happens if you're out of business when I have a warranty claim? (Honest answer: the manufacturer's parts warranty travels with the system; the labor warranty doesn't.)
5. “What's included in the install — and what's not?”
This is the question that catches every gotcha. Get it in writing. Specifically:
- Pad replacement. The concrete or composite pad under the outdoor condenser. New install or relocate? $150-$300 if not included.
- Disconnect upgrade. Sometimes required by code if your existing disconnect is old. $200-$400.
- Drain line. Replace or just reuse? Drain line should always be replaced on a swap.
- Thermostat. New install includes a basic programmable thermostat? Or are you upgrading to a Nest/Ecobee/Honeywell?
- Permit fee. Pass-through cost or absorbed?
- Removal/disposal of old equipment. EPA refrigerant recovery is required by law; verify it's included.
- Ductwork modifications. The single biggest hidden cost. New AC tonnage often requires duct upsizing on the supply side. Get this clarified before signing.
The right answer is a written line-by-line breakdown of the contract. The wrong answer is “don't worry, we'll handle it.”
One bonus question
“Can I have three references in my city, addresses included?”
Honest answer: yes, here are five names and addresses of recent jobs. Drive by, ask the homeowners.
Dishonest answer: “we have a five-star Google rating” (which can be bought) or “our customers are private” (which is nonsense for an HVAC installer).
If you'd like to interview me with these questions before signing anything, call (866) 982-3652. I'll answer every one of them honestly, in writing, and the in-home estimate is free.
Have HVAC questions? Call (866) 982-3652 or use the contact form. — Emilio Solano