Boiler Replacement Cost in Seattle, Washington
Our 2026 estimate for boiler replacement in Seattle, WA is $8,200 to $18,500. That puts Seattle 48% above the national average, mainly because of higher incomes and home values, which push labor rates up and the bigger heating equipment this climate calls for.
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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
- Leaks, rust, or pressure that keeps dropping
- The boiler is 20 to 30 years old or more
- Some radiators stay cold
- The pilot or ignition keeps failing
What Moves the Price
- Pumps, zone valves and the piping around the boiler
- A new chimney liner or venting
- Fuel type: gas, oil or propane
- A combi boiler that also makes your hot water
- Condensing or non-condensing boiler
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
- The new boiler and the piping around it
- Flushing and refilling the system
- Venting and fuel hookups
- Removing the old boiler
- Startup and safety tests
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
- A combi boiler frees up space and replaces your water heater.
- Ask for a heat-loss calculation. A lot of old boilers are much bigger than the house needs.
- For a steam system, hire a contractor who works on steam regularly.
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Boiler Replacement Questions from Seattle Homeowners
How much is boiler replacement in Seattle?
Plan on $8,200 to $18,500, with most jobs near $13,900. Equipment efficiency, house size and the condition of the ducts and wiring decide where your quote falls.
When is the best time to schedule boiler 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 long does a boiler last?
A cast-iron boiler can last 25 to 35 years. A modern condensing boiler usually lasts 15 to 20 with yearly service.
Can I replace a boiler with a heat pump?
Yes, with an air-to-water heat pump or a ductless system. The radiators may need upgrading, because heat pumps run cooler water than boilers.
Boiler 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.