Furnace is 15 years or older and repair calls are becoming frequent
Heating · Mercer Island, WA
Furnace Replacement in Mercer Island, WA
Most furnace replacements on Mercer Island run $4,800 to $9,800 installed, depending on furnace size and ductwork condition. SPS Pro Services has replaced furnaces across King County since 2017, and we can usually schedule a Mercer Island install within the same week you get your estimate.
Typical cost$4,800–$9,800
WarrantyWorkmanship warranty
AvailabilitySame-week visits
HoursMon–Fri 8am–6pm
Mercer Island sits surrounded by Lake Washington, and that waterfront exposure means homes here deal with more sustained humidity and wind-driven cold than inland Bellevue or Redmond properties. Furnaces work harder to recover after damp, breezy nights, and that extra cycling wears down heat exchangers and blower motors faster than in drier parts of King County.
Local knowledge
What's different about furnace replacement in Mercer Island
We run service calls in Mercer Island every week — the same patterns come up again and again.
Many Mercer Island homes were built in the 1950s through 1970s and still run original galvanized ductwork in crawlspaces that stays damp from lake proximity, which corrodes furnace cabinets and connections over time.
Island homes often have large view windows facing the water, and single-pane or older double-pane glass drives heat loss that pushes an undersized furnace past its rated capacity during winter cold snaps.
PSE serves gas and electric service on Mercer Island, and we size replacement furnaces to your actual PSE gas line capacity and panel setup rather than a generic load calculation.
Symptoms we see daily
Signs you need furnace replacement in Mercer Island
Uneven heating between rooms or a thermostat that won't hold temperature
Energy bills climbing with no change in how the home is used
Pilot light burns yellow instead of blue, or you notice odd smells when it runs
Banging, rattling, or grinding noises when the furnace starts up
No surprises
How a Mercer Island furnace replacement visit works
1
On-site load assessment
We inspect your current furnace, ductwork, and home's insulation and window exposure to calculate the correct BTU output for your Mercer Island address.
2
Written estimate same visit
You get a firm price within the $4,800 to $9,800 range before we schedule anything, based on furnace tier and any duct or venting work needed.
3
Old unit removal and disposal
We disconnect gas, electrical, and ductwork connections and haul away the old furnace, including any asbestos-era duct wrap inspection if your home dates to the 1960s or earlier.
4
New furnace install and connection
We set the new unit, connect gas and PSE electrical service, seal duct joints, and pressure-test the system before startup.
5
Startup, testing, and walkthrough
We run heating cycles, check airflow at each register, verify carbon monoxide safety readings, and walk you through the thermostat and filter schedule.
Flat-rate pricing
Furnace Replacement in Mercer Island — what it costs
Conservative ranges for the Seattle metro. Your written quote is exact before work begins.
| Job | Typical price |
|---|---|
| In-home estimateExact flat quote for your home | Free |
| Standard furnace replacementTypical single-system job | $4,800–$6,470 |
| Mid-range furnace replacementHigher-capacity or multi-zone equipment | $6,470–$8,130 |
| Complex furnace replacementPremium equipment or difficult access | $8,130–$9,800 |
Prices reviewed by Sergei Petrov · July 2026. Parts availability can shift ranges — the quote you sign is final.
24/7 Emergency Line
Emergency dispatchNo heat at 11pm? We pick up.
Office hours are Mon–Fri, but the emergency line never closes. Call any hour and we dispatch a licensed tech across Greater Seattle.
Straight answers
Furnace Replacement in Mercer Island — FAQ
How long does a furnace replacement take on Mercer Island?
Most single-family homes on Mercer Island are done in one day, roughly 6 to 8 hours, assuming the ductwork and gas line are in good condition. Crawlspace access issues common in older island homes can add extra time for the crew.
Why does my furnace need replacing sooner than a friend's in Bellevue?
Mercer Island's lake-surrounded location means higher ambient humidity year-round, which speeds up corrosion in heat exchangers and duct connections compared to drier inland neighborhoods, shortening typical furnace lifespan by a few years.
Do you handle permits for furnace replacement on Mercer Island?
Yes, we pull the required mechanical permit through the applicable jurisdiction and schedule the inspection so your new furnace is fully code-compliant, which matters for resale given how many Mercer Island homes get inspected during sale.
Can you size a furnace for a home with a lot of window glass facing the lake?
Yes, we account for glass exposure and orientation toward Lake Washington in our load calculation, since large view windows on the water side lose heat faster than standard wall construction and change the BTU output you actually need.
Founder & Lead HVAC Technician, SPS Pro Services
EPA Section 608 UniversalNATE Core Certified14+ years in the trade
Reviews the pricing and service guidance on this page against SPS Pro Services's actual job records in Mercer Island and across the Seattle metro.
Prices reviewed July 2026
Also in Mercer Island
Other services our crew handles on the same routes.
Need furnace replacement in Mercer Island?
Call (206) 427-8907 to get a firm furnace replacement estimate for your Mercer Island home this week.