Replacing a furnace, AC or heat pump usually means hiring a contractor. Federal agencies publish advice on how to choose one. This guide pulls together what ENERGY STAR, the Federal Trade Commission (FTC) and the U.S. Environmental Protection Agency (EPA) say. It also covers a sizing standard from a trade group, the Air Conditioning Contractors of America (ACCA). For state-by-state license lookups, see our guide to checking an HVAC contractor's license.
A hiring checklist from federal sources
| Step | What the source says | Source |
|---|---|---|
| Check the license and insurance | Confirm the license with your state or county and ask for proof of insurance | FTC (July 2022) |
| Size the system | Use your home's actual characteristics, not a rule of thumb | ENERGY STAR |
| Compare bids | Compare cost, energy efficiency and warranties | ENERGY STAR |
| Sign a written proposal | List project costs, model numbers, job schedule and warranty information | ENERGY STAR |
| Let the contractor get the permit | A contractor who asks you to get permits is a scam warning sign | FTC (July 2022) |
| Ask about refrigerant certification | Technicians who maintain, service, repair or dispose of equipment that could release refrigerants must be Section 608 certified | EPA |
Check the license and insurance first
ENERGY STAR's hiring tips say, "Find out about license and insurance requirements for contractors in your state." The FTC's home improvement scam guide is dated July 2022. It says, "Consider only contractors who are licensed and insured. Check with your state or county government to confirm a contractor's license, and ask the contractor for proof of insurance."
The rules and lookup tools differ by state. Our license guide covers Arizona, Washington, Texas, Florida and Ohio.
How a contractor should size your system
ENERGY STAR says, "A bigger system isn't always better; a contractor should size the heating and cooling system based on the size of your house, level of insulation, and windows." ENERGY STAR's quality installation page gives more detail. It says your contractor should use "the actual characteristics of your home to determine the equipment that is right-sized for your home." It says not to "just rely on a 'rule of thumb.'"
ACCA publishes Manual J. ACCA says, "Manual J 8th Edition is the national ANSI-recognized standard for producing HVAC equipment sizing loads for single-family detached homes, small multi-unit structures, condominiums, townhouses, and manufactured homes." ACCA also says a proper Manual J load calculation "is required by national building codes and most state and local jurisdictions." We did not check the code text ourselves to confirm ACCA's statement.
Jacksonville's residential permits page has a Manual J rule. The rule covers new space, not replacements. The page asks for "three sets of energy calculations and Manual J when the work involves a new space that is heated or cooled." For a replacement, you can still ask a contractor how they sized the new system.
How to compare bids
ENERGY STAR says, "When comparing contractors' proposals (bids), be sure to compare cost, energy efficiency and warranties." The FTC says, "A written estimate should include a description of the work to be done, materials, completion date, and the price." It adds, "Don't automatically choose the lowest bidder."
ENERGY STAR also says to "Sign a written proposal with a contractor before work gets started." It says the proposal protects you "by specifying project costs, model numbers, job schedule and warranty information." Our guide to SEER2 ratings covers the federal efficiency minimums to compare against.
What to put in the contract
The FTC says that before you sign a contract, you should make sure it includes:
- The contractor's name, address, phone number and license number
- An estimated start and completion date
- Any promises made during conversations or calls, such as the scope of work and the cost of labor and materials
- A written statement of your right to cancel within three business days if you signed it at home or anywhere other than the seller's permanent place of business
The FTC adds, "And, make sure all blank spaces are filled in." It says some states limit how much a contractor can ask for as a down payment. It says to contact your state or local consumer agency about the law where you live. It also says, "never make the final payment until the work is done and you're satisfied with it."
Your right to cancel under the Cooling-Off Rule
The FTC's Cooling-Off Rule page says, "The Cooling-Off Rule gives you three days to cancel certain sales made at your home, workplace, or dormitory, or at a seller's temporary location, like a hotel or motel room, convention center, fairground, or restaurant."
The rule does not cover every in-home sale. The FTC says it does not cover sales "needed to meet an emergency." It also does not cover repairs or maintenance that you asked the seller to come to your home to do. Anything you buy beyond that request is covered. An emergency AC replacement may not qualify.
Warranties and service contracts
The FTC's warranties guide is dated July 2023. It says, "Whenever there's a warranty, the law says it must be available for you to read before you buy." It also says, "If a salesperson makes a spoken promise, like saying the company will give you free repairs, get the promise in writing."
The FTC describes a limit that federal law puts on warranties. Under that law, a manufacturer can't make you use specific parts or services to keep your warranty coverage. The exception is when the manufacturer "gives you the parts and services for free or gets a waiver from the FTC to make that requirement." The FTC adds, "An extended warranty or service contract costs extra and is sold separately from a product."
Who should get the permit
The FTC lists this among the signs of a scam: "Scammers ask you to get any required building permits." Washington's Department of Labor & Industries has a Hire Smart guide. It says, "In most instances, if you have hired a contractor, the contractor is required to take out the permits." Permit rules vary by city. Our guide to HVAC permits covers five cities.
Refrigerant certification for technicians
EPA's Section 608 page was last updated July 15, 2026. It says, "EPA regulations (40 CFR Part 82, Subpart F) under Section 608 of the Clean Air Act require that technicians who maintain, service, repair, or dispose of equipment that could release refrigerants into the atmosphere must be certified." It also says, "Section 608 Technician Certification credentials do not expire." You can ask whether the technicians who will handle your system's refrigerant are certified.
What ENERGY STAR says to expect at installation
ENERGY STAR's quality installation page says to make sure "your contractor tests and adjusts the system's refrigerant charge for optimal comfort and efficiency." It also says, "Ask your contractor to inspect your home's duct system, perform a leakage test, and make necessary repairs." For more on new equipment, see our guides to central air conditioning, furnaces and the R-410A phase-out.