How long does a furnace last in Seattle?

When does furnace age start to matter?

Age becomes a decision factor the first time a repair quote crosses a few hundred dollars. On a 6-year-old furnace, you fix it without a second thought. On a 15-year-old furnace, the same failure is a fork in the road — because the next failure is already queued up behind it.

Seattle's heating season is long: your furnace runs from October into May in most homes. That's more accumulated runtime per calendar year than a national average suggests, which is why local systems often age faster than the sticker lifespan implies.

Burien and West Seattle homes with original equipment from the 1980s–90s are now hitting the 15–20 year window in clusters — which is why we see replacement waves follow housing booms by roughly two decades. Knowing your furnace's install year (sticker inside the cabinet) gives you a honest timeline.

The signs a furnace is aging out

The pattern we see on service calls, in rough order: heating bills creep up with no rate change to explain them, rooms heat unevenly, the unit short-cycles or runs longer to hit the same temperature, and burner or blower noises change character.

• Repairs are getting closer together — two in the same season is the classic signal
• Yellow or wavering burner flame instead of steady blue
• Visible rust or corrosion around the cabinet or flue
• The system pre-dates 2010 (80% AFUE era) and bills show it

Why maintenance decides the lifespan

A furnace is a heat engine with a filter problem. Restricted airflow — dirty filters, crushed returns, closed registers — makes the heat exchanger run hotter than designed, and thermal stress is what cracks heat exchangers. A cracked heat exchanger is the classic end-of-life failure: it can leak combustion gases and is rarely worth replacing on an old unit.

Annual professional maintenance keeps combustion tuned, verifies airflow, and catches the cheap failures (ignitors, sensors, capacitors) before they cascade into expensive ones. It also creates the service record most manufacturers ask for when honoring parts warranties.

What replacement looks like when the time comes

Replacement is a one-to-two-day job in most Seattle homes: the new furnace, code-required venting corrections, permit, and disposal. Modern condensing furnaces run 90%+ AFUE versus the ~80% of older units, which is a real monthly difference across a Puget Sound heating season.

Many Seattle homeowners also use the replacement moment to price a heat pump — Washington's mild winters suit them, and utility conversion rebates only apply at replacement time.

PSE pays $3,000–$4,000 for qualifying gas-to-heat-pump conversions; Seattle Clean Heat pays $2,000–$6,000 for oil conversions. Those rebates exist at replacement — not as retroactive credits after you've already bought equipment on impulse during a cold snap.

What does it cost in the Seattle area?

For context when the repair-versus-replace math starts, the typical Seattle-area ranges:

• Repair pricing depends on the failed part — ignitors and sensors sit at the low end, control boards and gas valves at the top
• Replacement pricing moves with size, AFUE tier, and any venting or code corrections your home needs
• Seattle-area permits commonly add $150–$450 to a replacement

These are typical Seattle-area market ranges compiled from published cost guides (Angi, HomeGuide, and Seattle-area 2025–2026 cost studies) — market context, not a quote from Glendale Heating & Air Conditioning. Your home's size, equipment, ductwork, electrical, and permits change the number. National figures are marked; Seattle-area labor typically runs above national averages.

Questions Seattle homeowners ask

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