Questions to ask before you hire an HVAC contractor in Seattle
Seattle’s mild, damp winters make heating the main job for most HVAC systems, but the June 2021 heat wave, when Seattle hit an all-time record of 108°F, and recurring late-summer wildfire smoke have many households adding cooling and better filtration for the first time. Some older Craftsman and mid-century homes still burn heating oil from an aging underground tank, many houses and apartments heat with electric baseboards and have no ducts, and others run on Puget Sound Energy natural gas. In Seattle, a split-system heat pump or air conditioner needs a City refrigeration permit that only a City-licensed refrigeration contractor can get, on top of Washington L&I contractor registration and separate rules for the electrical work. Use these questions to compare Seattle-area HVAC contractors on verified credentials, honest sizing, the right system for your house, and a written scope, not just who can come out this week.
Questions to ask
1. What is your Washington L&I contractor registration number, do you hold a City of Seattle refrigeration contractor license, and can I see both?
Why it matters: Washington requires every construction contractor to register with the Department of Labor & Industries (L&I) and to carry a surety bond and general liability insurance (L&I contractor registration), state law requires the registration number in all of the contractor’s advertisements, and you can usually find it on the written bid (L&I Hire Smart). Look it up with L&I’s Verify a Contractor, Tradesperson or Business tool, which also shows bond and insurance status, workers’ comp coverage, citations, and lawsuits against the bond. Inside Seattle city limits there is one more layer for heat pumps and air conditioners: a business that installs, repairs, or alters refrigeration or air-conditioning equipment needs a City of Seattle refrigeration contractor license and must designate an employee who holds a journey refrigeration mechanic license (SDCI refrigeration licensing). Only a licensed refrigeration contractor can get the refrigeration permit for a split-system heat pump or AC, and the contractor also needs a Seattle business license, even if its office is outside the city (SDCI refrigeration permit). Bellevue, Shoreline, Renton, and other nearby cities set their own permit rules, so ask what your city requires. Ask for a current certificate of insurance too.
2. Who will do the electrical work: is your company a licensed Washington electrical contractor, and who will run the new circuit and disconnect?
Why it matters: In Washington, electrical work is licensed separately from HVAC. Many HVAC technicians hold the HVAC/refrigeration (06A) specialty electrician certificate, which covers control wiring and line-voltage parts inside the equipment. Under the current rule, the 06A specialty does not cover new branch circuits, panelboards, conduit runs, or most disconnect switches outside the unit (WAC 296-46B-920). So a new 240-volt circuit and disconnect for a heat pump or condenser usually needs an electrician certified for that work (for example, a journey-level general or residential specialty electrician), either on the HVAC company’s staff or as a subcontractor. Inside Seattle, the City’s Construction and Inspections department (SDCI), not L&I, issues electrical permits and does the inspections, and any professional pulling one must have a Washington State electrical contractor’s license and a Seattle business license (SDCI electrical permit). Outside Seattle, the permit comes from L&I or from one of the cities that run their own electrical program (L&I city electrical permits). Ask who holds the electrical license, whether the electrical permit is in the quote, and whether your panel has room for the new load.
3. Which technicians on my job hold EPA Section 608 certification and the right Seattle refrigeration mechanic license, and are they trained on the newer A2L refrigerants?
Why it matters: Anyone who installs, services, or repairs equipment containing refrigerant must hold EPA Section 608 certification; the only exception is a registered apprentice who is closely and continually supervised by a certified technician (EPA Section 608 technician certification requirements; EPA Section 608 Q&A). In Seattle, the mechanic installing a system assembled on site must also hold a City refrigeration mechanic’s license appropriate for the refrigerant used (SDCI refrigeration permit). Since Jan. 1, 2025, EPA rules have limited new residential air conditioners and heat pumps to refrigerants with a global warming potential under 700 (EPA Technology Transitions), so many newer systems use A2L (lower-flammability) refrigerants such as R-454B or R-32, which EPA lists as acceptable only under specific use conditions (EPA SNAP) and which have their own handling and installation requirements. Ask who on the crew is certified and licensed, whether they have installed the refrigerant your proposed system uses, and how they will recover the refrigerant from the unit they remove. If your old AC or heat pump runs on R-22, ask plainly whether a repair still makes sense or whether replacement is the honest answer.
4. Will you run a Manual J load calculation for my house in Seattle’s climate, instead of matching the old furnace’s size?
Why it matters: Seattle winters are long, cloudy, and mild, with occasional cold snaps and snow, so many homes need steady, moderate heat for months rather than a big burst on a few days. Summers are usually mild too, but the June 2021 heat wave set Seattle’s all-time record of 108°F (NOAA Climate.gov), and many homes were built without air conditioning. A Manual J (or equivalent) load calculation should account for local design temperatures, insulation, windows, air leakage, and where the ducts run, and you should get the results in writing. Oversizing is common in older Seattle homes when each replacement was matched to the last furnace, and an oversized system short-cycles, wears out sooner, and can leave rooms uneven or clammy. Ask how the proposed system will handle a freezing week and a hot, smoky August afternoon, how it will keep upstairs bedrooms cool, and whether insulation or air sealing would let you buy smaller equipment. If electric heat will be your primary heat source, SDCI asks for a Heat Equipment Sizing Form with the electrical permit (SDCI electrical permit), so ask who prepares it.
5. Would a heat pump, a high-efficiency gas furnace, or a hybrid system fit my home, and if gas stays, will you combustion-test it and check venting and carbon monoxide safety?
Why it matters: Seattle’s mild winters suit heat pumps, which also add the air conditioning many homes lack, but you should still press on cold-weather performance. Ask for the manufacturer’s rated heating capacity at low outdoor temperatures, what backup heat is included (electric resistance strips or a gas furnace), at what outdoor temperature backup heat turns on, and what electric strips would mean for your panel and your Seattle City Light bill. A hybrid (dual-fuel) system pairs a heat pump with a gas furnace. Puget Sound Energy, which supplies natural gas in Seattle (PSE service area), sets technical requirements for its hybrid heat pump rebate, including a load calculation and a balance point of 30°F or below (PSE hybrid heat pump). Those are useful questions to ask any contractor quoting a hybrid. If you keep or install a gas furnace, ask whether the contractor will measure combustion and carbon monoxide with an analyzer and leave you the readings, where side-wall vents on a high-efficiency furnace will exit, how condensate will drain, and whether an old gas water heater will be left alone in an oversized chimney once the furnace stops venting into it. Under Washington law, residential buildings must have carbon monoxide alarms, but owner-occupied single-family homes legally occupied before July 26, 2009 are exempt until they are sold, when the seller must install alarms before the buyer moves in (RCW 19.27.530). Whatever your home’s status, ask the contractor to confirm you have working CO alarms near sleeping areas.
6. If my house heats with oil, how will you handle the conversion, and who decommissions the old oil tank?
Why it matters: The City estimates 8,000–10,000 Seattle homes still heat with oil, often from underground tanks that can rust and leak into soil and groundwater (Seattle Clean Heat Program). Ask whether the contractor regularly does oil-to-heat-pump conversions, how they will remove the old furnace and oil lines, and whether existing ducts can be reused. The Seattle Fire Department requires a permit before an underground residential heating oil tank is decommissioned, either removed or filled in place, and the work must be done or overseen by someone certified by the International Code Council (ICC) as an underground storage tank decommissioner (Seattle Fire Department rule). Tanks out of service for a year or more must be decommissioned (City oil tank flyer). Ask who is doing that work, whether it is in the quote, and who files the paperwork. If you discover or suspect a leak, the City flyer says to report it within 24 hours to 1-800-OILS-911 and stop automatic oil deliveries.
7. What will you check on ducts, filtration, and old materials that may contain asbestos, and is a ductless system better for a house with baseboards or radiators?
Why it matters: If you have ducts, ask whether they will inspect and pressure-test them and what sealing, balancing, or return-air fixes they recommend, especially for upstairs rooms that overheat in summer and finished basements. Wildfire smoke reaches Seattle in many summers, and Washington’s Department of Health recommends MERV 13 or higher filters if your HVAC technician confirms the system can handle them (WA DOH wildfire smoke ventilation guide), so ask about filter size, airflow, and how often to change it. Many Seattle homes and apartments heat with electric baseboards or hot-water radiators and have no ducts; ask whether ductless mini-splits make sense, how many indoor heads are really needed, where they will go, and how the line sets and condensate will be routed and covered outside. Older basements often have duct tape wrap, pipe insulation, or boiler and furnace insulation that may contain asbestos. The Puget Sound Clean Air Agency requires an asbestos survey before renovation; an owner who lives in their single-family house may do their own survey, but rentals, condos, and demolitions need an AHERA-certified inspector, and results must be shared with anyone who may disturb the material (Puget Sound Clean Air Agency). Ask how the contractor handles suspect materials before anyone cuts into them.
8. Which Seattle permits does my job need, who pulls them, will the outdoor unit need a noise review, and are inspections included?
Why it matters: In Seattle, SDCI requires a permit for any furnace replacement or alteration (a furnace or mechanical STFI permit), and a refrigeration permit for any split-system heat pump, air conditioner, or job that requires refrigeration piping; a homeowner can get a furnace permit, but only a licensed refrigeration contractor can get the refrigeration permit. SDCI inspects heat pumps, air conditioners, furnaces, and ducts at a cover inspection before anything is concealed and again at a final inspection (SDCI furnace and refrigeration permit FAQ). New or changed gas piping is permitted and inspected separately by Public Health – Seattle & King County, which covers Seattle, Clyde Hill, and unincorporated King County (Public Health gas piping permits), and in Seattle gas piping mechanics are licensed by SDCI (SDCI gas piping licensing). Electrical work needs its own SDCI electrical permit (see question 2). The same SDCI FAQ says heat pumps and air conditioners placed in a side yard need a noise review, lists property-line sound limits of 45 decibels for heat pumps, and 55 by day / 45 at night for air conditioners, and says ductless systems don’t need a noise review unless there is a complaint. Ask where the outdoor unit will sit, how loud the model is, and whether a noise review is needed. Ask the contractor to pull every permit in their company’s name, include permit fees in the quote, and schedule the inspections. Hold your final payment until the final inspection passes.
9. Which Seattle City Light, Clean Heat, or PSE programs might apply, and will you handle the paperwork?
Why it matters: Seattle City Light, which supplies electricity in the city, currently offers instant discounts on qualifying high-efficiency air-source heat pumps; the discount goes to the contractor through participating distributors, the amount depends on the unit’s efficiency ratings, your contractor can pass it on in the bid, so ask whether it is, and do-it-yourself installs don’t qualify (Seattle City Light heating and cooling). If you heat with oil, the City’s Clean Heat Program currently offers an instant rebate for switching from oil to a qualified heat pump (the City’s page currently names Mitsubishi Electric heat pumps) through a participating contractor, a bonus rebate for moderate-income households, and free heat pumps for income-qualified households through the Office of Housing. If you are a PSE gas customer converting a gas furnace to a hybrid system, PSE’s rebate is available only through a PSE Trade Ally or Recommended Energy Professional contractor (PSE hybrid heat pump). Ask which programs the contractor participates in, which equipment ratings each one depends on, who submits what and by when, and get any promised amount in writing as an estimate, not a guarantee. The federal Energy Efficient Home Improvement Credit (25C) ended for equipment placed in service after Dec. 31, 2025 (IRS), so a system installed in 2026 does not qualify for it; be wary of any quote that still counts a federal tax credit. Program rules and funding change, so verify current terms directly with each program before you sign.
10. What does the written estimate include: model numbers, line sets, electrical work, permits, oil tank or old equipment removal, and a labor warranty?
Why it matters: A good quote lists the exact indoor and outdoor model numbers, efficiency ratings, thermostat or controls, line set and line-set cover, pad or wall bracket, condensate drain or pump, duct changes, filter upgrade if included, electrical circuit and disconnect, permit fees (SDCI refrigeration, mechanical, and electrical, plus any gas piping permit), oil tank decommissioning if applicable, and disposal of the old equipment. Ask how they handle surprises like undersized ducts, asbestos-suspect material, a corroded chimney, or tight crawlspace or attic access, and require a stop-and-call change-order process before extra work. Get the manufacturer warranty and the contractor’s labor warranty in writing separately, and confirm who registers the equipment so the manufacturer warranty applies.
11. How do you handle no-heat calls in a cold snap and no-cooling calls in a heat wave, and can you give me recent Seattle-area references?
Why it matters: Seattle-area cold snaps and summer heat waves are usually short but intense, and every HVAC company gets slammed at once. Losing heat in freezing weather can freeze pipes in crawlspaces and exterior walls, and extreme heat is dangerous for older adults, young children, and anyone with health conditions. Ask what response time looks like for existing customers during those surges, what after-hours and weekend rates apply, whether a maintenance plan actually moves you up the list, and what an annual tune-up includes. Then ask for two or three recent local references for similar homes, such as an oil-to-heat-pump conversion in a Wallingford Craftsman, ductless heads in a baseboard-heated condo, or a hybrid system in a West Seattle rambler. References tell you about punctuality, cleanup, noise, and whether the system was set up right the first time, which star ratings alone often miss.
Red flags
Quotes a replacement size over the phone or by matching the old furnace, with no load calculation.
No Washington L&I registration number on the bid, or it doesn’t show as active with a bond and insurance in L&I’s Verify tool.
Installing a split-system heat pump or AC in Seattle without a City refrigeration contractor license, or asking you to pull the permit in your own name.
Can’t say who holds the Washington electrical contractor license or who will run the new circuit and disconnect.
Offers a lower price to skip permits or inspections.
Vague about which refrigerant the new system uses or who on the crew is EPA 608 certified.
Pitches a heat pump without explaining cold-weather capacity, backup heat, and what electric strips need from your panel.
Plans to leave an old oil tank in the ground without the Seattle Fire Department decommissioning permit, or won’t say who is certified to do it.
Puts an outdoor unit in a side yard without discussing noise limits, or won’t combustion-test a new gas furnace.
Disturbs old duct wrap, pipe insulation, or boiler insulation without talking about an asbestos survey.
No model numbers, no electrical or permit scope, and no written labor warranty on the estimate.
Promises a specific rebate as guaranteed, still counts the expired federal 25C credit, or isn’t a participating contractor for the program they’re promising.
Get at least two written quotes for the same scope, with model numbers, efficiency ratings, and electrical, permit, and disposal work listed.
Ask each contractor to share their load calculation and explain how the system handles a freezing week and a summer heat wave.
Confirm who holds the Washington electrical contractor license and who pulls the SDCI electrical permit.
Confirm the contractor pulls the SDCI refrigeration or furnace permit (and any Public Health gas piping permit) in their name and schedules the cover and final inspections.
Ask where the outdoor unit will go, how loud it is, and whether SDCI noise review applies.
If you heat with oil, confirm who handles the Seattle Fire Department oil tank decommissioning permit and work.
Ask about an asbestos survey before anyone disturbs old duct wrap or pipe insulation, and about a MERV 13 filter for smoke season.
Make sure you have working carbon monoxide alarms near sleeping areas, especially if you keep gas appliances.
Check current incentives directly with Seattle City Light, the Clean Heat Program, or PSE before you sign, and confirm your contractor participates.
Agree in writing on equipment placement, warranty terms, payment schedule, and a stop-and-call change-order process; hold final payment until inspection passes.
Keep the permit records, warranty registrations, and final invoice for resale and future service.