Quick answer
Repair when the furnace is under about 12 years old, the fix is a single component well under a third of replacement cost, and the heat exchanger is sound. Replace when the furnace is 15+ years old, the repair quote crosses the 50% threshold, repairs are repeating, or any safety-class failure appears — a cracked heat exchanger is a replacement, full stop, at any age.
- Typical Puget Sound furnace repairs run $250–$2,500; a full replacement runs $9,000–$15,000 — the ratio between those numbers drives the decision.
- Under 12 years old with a single failed part (igniter, capacitor, board): repair.
- 15+ years, second repair in two winters, or a repair quote over half of replacement: replace.
- Safety overrides economics: cracked heat exchangers and CO risks end the repair conversation.
- At end of life, price a cold-climate heat pump alongside the furnace — Washington rebates only support the switch.
Use this guide when
You're holding a repair invoice wondering if replacement is smarter before winter, your furnace just failed for the second time in two seasons, or a technician told you the whole system needs replacing and you want to pressure-test that verdict before spending five figures.
What actually drives the decision
Four questions: how old is the furnace against its 15–20 year expected lifespan, what's the repair-to-replacement ratio, is this the first failure or a pattern, and what rebates would apply to a replacement? A $600 repair on an 8-year-old furnace and the same repair on an 18-year-old one are completely different decisions.
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Repair signals
A single component failure — igniter, flame sensor, capacitor, control board, blower motor — on a furnace inside its first 12 years, especially with parts under manufacturer warranty. Most of these fixes land in the $250–$800 range and buy years of remaining service on a system that was healthy yesterday.
Replace signals
A cracked heat exchanger (at any age), 15+ years on the data plate, a repair quote past 50% of replacement, the second or third repair in two years, or gas bills creeping up with no usage change — old single-stage furnaces at 80% AFUE waste a fifth of every therm compared to modern condensing equipment.
The upgrade question at end of life
If you're replacing anyway, compare a like-for-like furnace against a cold-climate heat pump before signing. The heat pump adds cooling, runs at 2–4× the effective efficiency in our mild climate, and is where Washington's money sits: WA HEAR point-of-sale discounts up to $8,000 for income-eligible households plus PSE rebates of $500–$1,500. A new gas furnace earns essentially nothing.
Key terms and context
This guide is written for heating & air decisions in the Puget Sound. It uses the same terminology you'll hear from inspectors, technicians, and permit offices.
Repairing unsafe units
A cracked heat exchanger can leak carbon monoxide into your supply air, and no patch fixes it — the repair IS a new heat exchanger, which on an old furnace costs so much that replacement wins on every axis. If your furnace is red-tagged for a heat exchanger crack, treat it as a replacement decision, not a negotiation.
The serial-repair trap
Three $500 repairs across two winters is $1,500 spent renting time on a dying furnace — money that vanishes the day it finally quits, usually on the coldest week of January when every installer is booked. Track cumulative repair spend against the replacement quote and set a walk-away number in advance.
How we build this guidance
- Eco repairs and replaces furnaces across the Puget Sound — we profit either way, so the recommendation follows the diagnosis.
- Heat exchanger verdicts come with camera evidence, not just a red tag.
- Every replacement quote includes the rebate math (WA HEAR, PSE) so you compare real net prices.
Methodology: Thresholds follow the industry-standard 50% and repair-cost × age screens against a 15–20 year furnace lifespan; ranges align with Eco's published Puget Sound cost guides. Safety conditions (heat exchanger, venting, CO) override economics in every case.
Last updated: 2026-07-05
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Common questions
What's the 50% rule for furnace repairs?
If a repair costs more than half the price of a new system, replacement usually wins on total cost of ownership. A stricter screen multiplies repair cost by the furnace's age in years — when that product exceeds the replacement price, replace. With Puget Sound replacements running $9,000–$15,000, a $2,000 repair on a 14-year-old furnace fails both tests.
Is a cracked heat exchanger really not repairable?
Effectively no. The heat exchanger is the wall between combustion gases and the air you breathe, and replacing that one component on an out-of-warranty furnace costs a large fraction of a whole new system — for a furnace that's still old everywhere else. Ask to see the crack on camera, then make it a replacement decision.
Should I replace my furnace with another furnace or a heat pump?
In our mild marine climate, a cold-climate heat pump is usually the stronger buy at end of life: it heats and cools in one system and captures the rebates Washington aims at electrification — WA HEAR discounts up to $8,000 for income-eligible households plus PSE rebates of $500–$1,500. Keep gas when your furnace is young, or pair both in a dual-fuel setup for large homes.
Can I limp my furnace through one more winter?
Sometimes that's the honest answer — a cheap, eyes-open repair now and a planned replacement on your schedule. The risk is timing: furnaces fail on the coldest nights, when emergency replacement means paying rush prices for whatever's in stock. If yours is past 15 years, get the replacement quote now so the decision is ready when the furnace makes it for you.