AC Installation in Seattle, WA
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Seattle summers don't ask much of an air conditioner
Summer afternoons here average 70°F. That's mild, and it means a new air conditioner in King County isn't fighting the kind of heat that pushes a system hard, day after day, for months. It still needs to be sized and installed right for the times it does run.
Any central air conditioner installed new has to meet a federal minimum of 13.4 SEER2. That's the baseline a contractor will work from when they size a system for your home.
- 70°F
- the average summer afternoon it cools against
- 13.4 SEER2
- the federal minimum any new unit must meet
NOAA nClimDiv, 1991–2020 normals
Going above the federal minimum saves little here, about $10 a year.
Estimates for a typical King County home, from EIA household energy data, Washington fuel prices and NOAA climate normals. Your home will differ.
Washington requires contractors to register with the state.
That registration puts the business on file with the Department of Labor and Industries, along with proof of bond and insurance. Nobody tests the contractor's work before they hand over that number. It tells you the business exists and is covered if something goes wrong, not that the state checked what they know.
On this job, the check that matters is local. Installing an air conditioner needs a permit from the building office and an inspection once the work is done, in most cities and counties here. That inspection is what confirms the installation was done right. The registration does not cover that.
Source: Washington State Legislature
- What size air conditioner does my house need?
- The right size comes from a load calculation, not the square footage of your house. A contractor measures your windows, insulation, ceiling height, and how much sun each wall gets, then works out how much heat your house actually gains on a hot day. An oversized unit cools the air fast but shuts off before it pulls the moisture out, so rooms feel clammy. Seattle summer afternoons average 70 degrees, which is mild compared to most of the country, so a contractor sizing your system here will size it for those milder loads rather than guessing based on a hotter climate.
- Should I replace the whole system or just the outdoor unit?
- If your indoor coil and outdoor unit were installed together and matched for each other, replacing only the outdoor unit can throw off that match and hurt performance. Refrigerant changes have also made some older outdoor units hard to pair with new ones still on the market. A contractor can check whether your existing coil and any ductwork will work with a new outdoor unit before you decide. New units sold now have to meet a federal minimum of 13.4 SEER2, so whatever you replace will meet that baseline.
- Do HVAC contractors in Seattle need a state license to work on my home?
- Washington does not license HVAC contractors through a trade exam. What the state requires is registration with the Department of Labor and Industries, which is a business record showing the contractor is bonded and insured, not a test of their skill. Separately, installing an air conditioner in most Seattle homes needs a permit from the local building office, and the work gets inspected once it's done. Ask to see a contractor's L&I registration number and check that they pull the permit for your job.