Should I repair my furnace or replace it?
This is the repair-or-replace decision framework — not the furnace-vs-heat-pump comparison table. Under 10 years old: repair, almost always. Past 15: put major-repair money toward replacement. In between, weigh four inputs — age, what failed, the efficiency you'd gain, and how long you'll stay in the home. A cracked heat exchanger at any advanced age is the classic replacement trigger. Seattle's long October–May heating season and rising PSE gas rates tip borderline cases toward replacement sooner than national rules of thumb, especially when a heat-pump conversion would unlock Seattle City Light or PSE money at the same visit and your panel can support it.
The quick answer
- Under 10 years: repair. Past 15: major repairs rarely pencil out
- Cracked heat exchanger, failed control board, or gas valve on an old unit = replacement conversation
- Repairs clustering (two in one season) predict the next failure is queued
- Replacement resets efficiency (80% era → 90%+ AFUE) and starts a new warranty clock
When repair is the right call
The furnace is under ~10 years old, the failure is a chain part (ignitor, flame sensor, capacitor, pressure switch, inducer), and the unit has no repeat-failure history. These parts fail on good furnaces; fixing them buys years, and your parts warranty may still cover the component itself.
Repair also wins whenever the failure is actually an airflow or maintenance problem wearing a parts costume — a limit tripping from a clogged filter doesn't indict the furnace. Fix the cause, not just the casualty.
When replacement is the honest answer
The unit is 15+ years old and facing a major repair: heat exchanger, control board, gas valve, blower assembly. You'd be putting four figures into a machine at the end of its statistical life — with the next failure already accruing. A cracked heat exchanger specifically ends the conversation for safety reasons on any older unit.
Replacement also gets stronger if you're on the 80% AFUE era (pre-~2010): a modern condensing furnace keeps 90–99 cents of every gas dollar versus ~80, across Seattle's long October–May season. And if you want cooling anyway, the replacement moment is when adding AC — or switching to a heat pump with its rebate stack — costs least.
The in-between: make the math explicit
For the 10–15-year gray zone, one honest rule of thumb: multiply the unit's age by the repair quote — past roughly $5,000, lean replacement. It's a sanity check, not physics; what it forces is the right comparison. Ask any bidder for both numbers in writing: this repair, and this repair's cost credited against a replacement. We put both on second opinions for exactly this reason.
Utility territory belongs in the gray zone too: PSE gas customers facing a borderline repair on a 14-year-old furnace should price the heat-pump conversion rebate ($3,000–$4,000) in the same worksheet — SCL customers on electric resistance should check instant discount tiers. Stay horizon is the tiebreaker: repair buys time when you're two years from a remodel that changes the HVAC design; replacement wins when you're settled in a 1920s bungalow with another fifteen winters ahead.
What does it cost in the Seattle area?
The two numbers you're actually comparing, in Seattle-area market terms:
Repair visit / diagnostic
$150 – $450
Diagnostic fee plus a typical single-part repair
National figures — Seattle-area labor typically runs above. Sources: HomeGuide — HVAC repair cost (2026)
Gas furnace replacement
$4,000 – $9,000 typical ~$5,500
New high-efficiency furnace, installed — equipment, labor, permit
Sources: Home Comfort Alliance Seattle furnace guide (2026) · HVAC Project Cost — Seattle, WA (2026)
- Repair pricing scales with the failed part — ignitors and sensors low, boards and gas valves high
- A second same-season failure usually erases whatever the first repair saved
- Replacement pricing moves with size, AFUE tier, and venting/code corrections
- Considering a heat pump instead? Conversion rebates only exist at replacement time
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.
The traps on both sides
The endless-repair trap: a fourth repair on a 17-year-old furnace, each one 'cheaper than replacing,' until you've paid a third of a new furnace to keep an old one limping into the winter it finally quits. And the panic-replace trap: a scary quote on a no-heat morning for a unit that needed a $40 sensor. Both thrive on missing information.
The defense is the same either way: a diagnosis that names the failed part, its price, the unit's age, and the replacement math side by side. Any bid that resists writing that down has answered your question.
Pre-war Seattle stock adds a third trap: replacing a furnace without asking whether the ducts, flue, or panel are ready for what comes next. A 1990s 80% furnace in a Magnolia basement with an orphaned water heater on a shared chimney isn't just a furnace decision — it's a venting-and-electrification checkpoint. Repairing to buy time for that planning is valid; replacing in panic without the checklist isn't.
Questions Seattle homeowners ask
Is the age × repair cost > $5,000 rule legit?
As a sanity check, yes; as gospel, no. It compresses the real inputs (age, failure type, efficiency delta, your timeline) into one number. Use it to notice when a repair deserves scrutiny — then make the actual comparison with real quotes for both paths.
My furnace is 20 years old but runs fine. Replace it proactively?
No failure, no forced move — but do three things: keep maintenance current (its remaining life depends on it), budget as if replacement is near (because statistically it is), and get your replacement research done calmly now rather than during a no-heat week. Old-but-maintained furnaces mostly earn their retirement date honestly.
The repair quote seems huge. How do I know it's real?
Ask for the failed part by name, the diagnosis behind it, and the itemized price — then get a second opinion; ours is free on replacement-scale quotes. Legitimate quotes survive scrutiny comfortably. The scary ones that arrive with a same-day discount usually don't.
If I replace, is it worth switching to a heat pump?
Replacement time is exactly when that question pays: PSE's gas-to-heat-pump rebate runs $3,000–$4,000, you gain cooling, and the install premium over a furnace is smallest when you're buying equipment anyway. Work the heat-pump-vs-furnace guide — the answer depends on your panel, ducts, and timeline. Pre-war Seattle homes on 100-amp service often discover ductless or right-sized ducted heat pumps fit where a straight furnace swap ignored the electrification path entirely.
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How we know this
Framework reflects Glendale's second-opinion practice on Greater Seattle replacement quotes; lifespan statistics from our service history since 1938; cost ranges from published Seattle-area studies (Angi, HomeGuide, 2025–2026).
Reviewed by the Glendale Heating & Air Conditioning team · Last updated 2026-07-15
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