HVAC System Replacement Cost in Seattle, Washington
Expect to pay $12,600 to $27,400 for full HVAC system replacement in Seattle, WA. Most homeowners end up near $20,700, depending on the equipment tier and how much of the old setup can be reused.
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Seattle Weather and HVAC Load
In a normal year, Seattle racks up 4,482 heating and 210 cooling degree days (NOAA 1991-2020 normals). Heating is the bigger job here, and furnaces and heat pumps in Seattle put in far more hours than the air conditioner. On average, Seattle gets 25 freezing nights and 2 days above 90°F per year. Snowfall averages about 4 inches. For a 2,000 sq ft house, this climate points to a heating load somewhere near 55,000 BTU/h. Treat that as a starting number. A Manual J calculation will move it up or down based on insulation and windows.
| Heating degree days / year | 4,482 |
|---|---|
| Cooling degree days / year | 210 |
| Nights at or below 32°F | 25 |
| Days above 90°F | 2 |
| Average low / high | 45.7°F / 60.8°F |
Seattle Housing Stock
Census figures put the median build year in Seattle at 1974, so a typical house here has about 52 years on it. A lot of these homes are on their second or third system by now. The ductwork is usually original, and leaky joints are common. Seattle has roughly 156,000 owner-occupied homes, or 44.2% of households. Homes here have a median value of $912,100 and households a median income of $121,984. Those two numbers drive the labor adjustment in our estimate.
NOAA's Storm Events Database shows no hail or damaging-wind days for King County from 2020 through 2025, so storm damage to outdoor units is rare here.
When Replacement Makes Sense
- An old R-22 AC paired with an aging furnace
- Both the heating and cooling equipment are 15 years old or more
- Some rooms are uncomfortable, and the energy bills are high
What Moves the Price
- Efficiency ratings: SEER2, AFUE and HSPF2
- Equipment sized to the house and climate
- Duct repair or replacement
- Permits and electrical work
- Thermostat and zoning upgrades
- Furnace plus AC, or heat pump plus air handler
We raised the national figures about 48% for Seattle using local income, home values and the equipment size this climate needs. Real bids can still come in outside the range, so collect three written quotes.
What the Quote Should Cover
- Removing the old equipment
- Duct connections and sealing
- New, matched heating and cooling equipment
- A load calculation and system design
- Startup, testing and warranty registration
Washington Permits, Efficiency Rules and Rebates
Washington falls in the DOE's North region. New split central air conditioners must meet at least 13.4 SEER2, and heat pumps sold anywhere in the U.S. need 14.3 SEER2 and 7.5 HSPF2. Plan on a mechanical permit for most replacements in Seattle; the contractor normally pulls it. Before you sign, ask each bidder for their Washington license or registration number and proof of insurance. The federal 25C tax credit ended for equipment installed after December 31, 2025, so incentives now come mostly from utilities and state programs. Check your electric and gas utility's rebate page before you pick equipment.
Before You Hire
- Ask for a duct leakage test. Leaky ducts can lose 20 to 30% of what the system puts out.
- Replacing both pieces at once usually costs less than two separate jobs a few years apart.
- Make every bidder quote the same efficiency ratings, or the prices won't compare.
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HVAC System Replacement Questions from Seattle Homeowners
How much is full HVAC system replacement in Seattle?
Plan on $12,600 to $27,400, with most jobs near $20,700. Equipment efficiency, house size and the condition of the ducts and wiring decide where your quote falls.
When is the best time to schedule full HVAC system replacement in Seattle?
Between late spring and early fall. Seattle averages 25 freezing nights a year, and heating calls spike from November through February.
How often should an HVAC system be replaced?
Most systems get replaced every 15 to 20 years. AC units and heat pumps usually wear out before gas furnaces do.
Can I replace only the AC and keep my furnace?
Yes, as long as the indoor coil and blower work with the new AC. A mismatched system loses efficiency and can void the warranty.
HVAC System Replacement Near Seattle
Sources: U.S. Census Bureau ACS 5-year estimates 2019-2023 and 2024 population estimates; NOAA NCEI U.S. Climate Normals 1991-2020, station Seattle Sand Point Wsfo; NOAA Storm Events Database 2020-2025, King County. Prices are our estimates, not contractor quotes. Updated 2026.