Quick answer
Three questions decide almost every case: How old is it? How big is the repair? And what happens to the money afterward? A $300 igniter on a 5-year-old furnace is an easy repair. A $2,000 heat exchanger or blower assembly on a 12-year-old furnace is a down payment on the next breakdown — spent on a machine that burns more gas per degree than a modern replacement ever would. Our rule: any furnace over 10 years old facing a major repair should heavily consider replacement.
- Under ~8 years old with a minor repair: fix it. That's what maintenance and repairs are for.
- Over 10 years old with a major repair: replacement deserves serious consideration — often it's the clear financial winner.
- A useful industry rule of thumb: multiply the unit's age by the repair cost. Over ~$5,000, replace. (12 years × $600 = $7,200 → replace.)
- Big repairs on old furnaces buy you the same old efficiency; replacement buys you 96%+ AFUE, staged comfort, and a fresh warranty.
Last updated: 2026-07-16 · Written & reviewed by the Eco field team
Repair vs replacement at a glance
| Repair Makes Sense | Replacement Wins | |
|---|---|---|
| Age | Under ~8 years | Over 10 years (PNW furnaces typically live 8–10) |
| Repair type | Minor: igniter, flame sensor, capacitor, thermostat | Major: heat exchanger, blower assembly, inducer, control board on an old unit |
| Repair history | First or second repair | A repair every season — the pattern is the message |
| The math | Age × repair cost well under $5,000 | Age × repair cost over $5,000 |
| Bills | Stable | Creeping up as efficiency degrades |
| Safety | No safety issues | Cracked heat exchanger = replacement, full stop |
| What the money buys | More life from a machine with life left | 96%+ AFUE, new warranty, right-sized system — and the chance to fix duct problems |
The age × cost multiplication rule is the industry-standard framing, stated as the rule of thumb it is — a framework, not a quote.
The math nobody runs at 9 pm when the heat is out
Repair decisions get made under pressure — the house is cold and the technician has a quote. So here's the framework to hold onto. First, age: ENERGY STAR recommends considering replacement for furnaces near the end of their service life, and in the Puget Sound our field data puts typical furnace life at 8–10 years. Second, the multiplication rule the industry uses: age × repair cost. A $700 repair on a 4-year-old furnace scores 2,800 — repair it. The same repair on an 11-year-old scores 7,700 — that money belongs in a new system. Third, the efficiency gap: a decade-old 80% furnace sends 20 cents of every gas dollar up the flue; a new condensing unit sends a nickel. Every winter you keep the old machine alive, you pay that spread.
Which repairs should always trigger the conversation?
A cracked heat exchanger — this isn't a judgment call. It's a carbon monoxide pathway, the repair costs a large fraction of a new furnace, and on an older unit it's the definitive replacement signal. A blower motor or assembly on a 10+ year unit — often $1,000–$2,000 installed, on a component whose failure is frequently a symptom of a deeper problem. An inducer motor or control board past year 10 — individually repairable, but at this age they arrive in clusters, and paying for them one at a time is the most expensive way to buy a new furnace. And anything failing twice — a component that fails again after replacement means the system is killing its parts. Diagnose the system, not the part.
The hidden culprit: your ducts may be killing your furnace
Here's what a repair-only visit never tells you. Furnaces and air handlers are rated by their manufacturers for a maximum external static pressure — commonly around 0.5 inches water column (it's printed in the installation manual of every Goodman, Trane, Carrier, and Daikin unit, and tabulated in BPA's manufacturer lookup tables). Undersized returns, crushed runs, and restrictive filters push systems far past that number, and high static pressure kills equipment: blower motors overheat and fail early, heat exchangers overheat and crack, and airflow starvation cascades into exactly the major repairs listed above. It can also jeopardize warranty coverage, because manufacturer warranties exclude failures caused by improper application. If your furnace is eating parts, ask for a static pressure reading before you pay for the next one — and if you replace, fix the duct problem with the new install, or the new furnace inherits the old killer.
What does replacement buy that repair can't?
Efficiency: 80% → 96%+ AFUE means roughly 16% less gas for the same heat, every year. A warranty clock reset — 10-year parts warranties are standard on registered new equipment. The chance to right-size: most old furnaces were oversized, and replacement is the only moment to fix sizing, staging, and duct restrictions together. And the heat pump question: if you're replacing anyway, this is the exact moment to compare a heat pump on the same ducts — rebates apply to that path, and not to a new gas furnace.
Pros and cons, honestly
Repair makes sense
Pros
- Furnace under ~8 years old with a minor repair (igniter, flame sensor, capacitor, thermostat)
- First or second repair — no pattern yet
- Age × repair cost lands well under $5,000
- Bills stable, no safety issues
Cons
- More life from a machine with life left — but no efficiency gain
- Past year 10, repairs tend to arrive in clusters
Replacement wins
Pros
- 96%+ AFUE, a new 10-year parts warranty, and a right-sized system
- The one moment to fix sizing, staging, and duct restrictions together
- The natural moment to price a heat pump on the same ducts — with rebates
Cons
- Bigger upfront spend — though a major repair on an old unit is a down payment on the next breakdown
- Cracked heat exchanger = replacement, full stop — no judgment call
The pattern is the message
A repair every season isn't bad luck — it's the system telling you something. A furnace that keeps eating blower motors usually has high static pressure from restrictive ducts or filters forcing the motor to work beyond its rating. Get the pressure measured before buying motor number three, and never pay for major components one at a time on a unit past its typical service life.
The verdict, by situation
Repair
Young furnace, small part — fix it
Under ~8 years with an igniter, sensor, or capacitor on the quote, repair is the obvious answer. That's what maintenance and repairs are for.
Replace
Old furnace, major repair — run the math
Past year 10, four-figure repairs buy the same old efficiency on a unit whose parts now fail in clusters. The age × cost rule usually points at replacement — and at pricing a heat pump on the same ducts while rebates apply.
Either way
Get the static pressure measured first
If your furnace is eating parts, the duct system is often the killer. A static pressure reading costs minutes and tells you whether a new furnace would inherit the same problem.
Which Washington households this sounds like
The 12-year-old furnace with a $1,500 blower quote
Age × cost lands at 18,000 — far past the line. That money belongs in a new system, and this is the exact moment to compare a heat pump on the same ducts.
The 5-year-old furnace that won't ignite
An igniter or flame sensor is a consumable. Repair it, keep up annual service, and expect years more life.
The furnace on its third blower motor
The system is killing its parts — almost always high static pressure from restrictive ducts or filters. Diagnose the system before buying motor number three.
The January no-heat emergency
A like-for-like swap is usually a one-day job when you need heat this week — but a free second opinion on the repair quote costs nothing and often changes the plan.
How we build this guidance
- We do both — repairs and replacements — so the honest answer costs us nothing either way.
- Age guidance follows ENERGY STAR recommendations plus our PNW field lifespan data; the age × cost rule is the industry-standard framing, stated as the rule of thumb it is.
- Every replacement quote from us includes a static pressure reading — because installing new equipment on a duct system that killed the last one isn't a solution.
Methodology: Replacement thresholds per ENERGY STAR guidance; static pressure ratings per manufacturer installation manuals and BPA PTCS lookup tables; efficiency comparison from AFUE ratings.
Ready for the next step?
Get a free estimate for your actual house, not a hypothetical one — honest numbers and rebate eligibility checked before any work begins.
Continue exploring
- Learn: How long does an HVAC system last in the PNW? →
- Learn: Furnace vs heat pump — which should heat your Puget Sound home? →
- Learn: Why is my furnace short cycling? →
- Learn: When should you replace your ductwork? →
- Evaluate: Repair vs replace — the decision framework →
- Compare: Single-stage vs two-stage vs variable-speed furnaces →
- Compare: Condensing vs non-condensing furnaces →
- Book: Furnace repair and replacement estimates →
Common questions
Is it worth repairing a 12-year-old furnace?
For a minor repair — an igniter, a sensor — sometimes, to buy a planned transition instead of an emergency one. For a major repair, rarely: at 12 years a Puget Sound furnace is past its typical 8–10 year service life, and four figures spent there is four figures not spent on equipment that's more efficient, under warranty, and not next to fail.
What counts as a “major” repair?
Heat exchanger, blower motor or assembly, inducer motor, gas valve, or control board — roughly anything north of $800–$1,000 installed. Minor repairs are the consumables: igniters, flame sensors, capacitors, thermostats.
My furnace keeps eating blower motors. Why?
That pattern is almost never bad luck — it's usually high static pressure from restrictive ducts or filters forcing the motor to work beyond its rating. Manufacturers rate systems for a maximum external static pressure (typically ~0.5" w.c.); running above it shortens motor life dramatically. Get the pressure measured before buying motor number three.
Should I replace my furnace with another furnace or a heat pump?
If you're replacing anyway, price both. The heat pump path carries Washington rebates, adds cooling, and fits our climate exceptionally well; the furnace path costs less upfront. We quote them side by side — the comparison is the whole point of our Furnace vs Heat Pump guide.
Sources & references
Equipment ratings, program details, and industry figures on this page come from manufacturers and primary sources, linked below. Verify program status and requirements for your home where applicable.
Repair vs replace guidance
- ENERGY STAR guidance on when to consider replacing aging heating and cooling equipment — ENERGY STAR — Heating & Cooling: When Is It Time to Replace?
Static pressure & equipment ratings
- Residential air handlers and furnaces are rated for a maximum external static pressure — commonly 0.5 in. w.c. — printed in the installation manual — Goodman Manufacturing — AVPTC Air Handler Installation Instructions
- Rated external static pressure and airflow specifications, compiled by manufacturer and model — Bonneville Power Administration — PTCS ESP & CFM Lookup Tables
- How static pressure is measured and interpreted, and how excessive static degrades airflow and equipment operation — National Comfort Institute — Measure and Interpret Static Pressures (hosted by ENERGY STAR)
Warranty terms
- Manufacturer limited warranties exclude damage or repairs required as a consequence of faulty installation or application — Goodman Manufacturing — What problems does the limited warranty not cover?
Equipment lifespan (our published data)
- Puget Sound service-life figures: furnaces 8–10 years, central ACs 12–15, heat pumps 15–20+ with annual service — Eco — How Long Does an HVAC System Last in the PNW?