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How long do furnaces last?

A gas furnace typically lasts 15–25 years. Where yours falls in that range depends on how hard it works, how it's been looked after, and (for tank water heaters) your water. The best predictor is its age, which is coded in the serial number.

TypeTypical lifeReplacement cost (installed)
Gas furnace15–25 years$3,800–$10,000

How old is yours?

Enter the serial number from the data plate. We'll decode the manufacture date and tell you how much typical life is left, adjusted for your state.

Brand guides: Rheem · Ruud · Goodman · Amana · Daikin · Carrier · Bryant · Payne · ICP · Trane · American Standard · Lennox · York· Where to find the serial number

Where your furnace is in its life

TypeEarly lifeMid-lifeNearing the endPast typical life
Gas furnaceunder 8 yrs8–12 yrs12–25 yrsover 25 yrs

Stage cut-offs are our own rule of thumb (half and 80% of the low end of the typical range), used to decide when a repair stops being worth it.

What wears furnaces out faster

These are estimates. The direction is supported by the sources below, but nobody has measured the size of the effect, so treat them as a rough guide. Our decoder applies them automatically when you pick your state.

Repair or replace?

We compare the repair bill with the cost of a new unit, and get stricter as the unit ages:

StageRepairRepair, but plan to replaceReplace
Early lifeAny repair (check the warranty first)——
Mid-lifeunder 30% of replacement30–50%over 50%
Nearing the endunder 15%15–30%over 30%
Past typical life—under 15%over 15%

Example: a new gas furnace costs about $6,900 installed (midpoint of $3,800–$10,000). Once it's 12+ years old, a repair over about $2,070 points to replacing.

The 30% and 50% marks are widely used contractor rules; the stricter bands for older units are our own. If a new, more efficient unit would pay for itself in energy savings within half its life, we lean toward replacing. A cracked heat exchanger means replacing regardless of cost: it is a safety problem, not a repair.

Typical repair costs

RepairTypical cost
Flame sensor$80–$250
Igniter$100–$250
Control board$300–$650
Draft inducer motor$400–$1,100
Blower motor$500–$2,300
Heat exchanger$1,000–$3,000

Published 2026 ranges from national cost guides. Prices vary a lot by region and contractor; get a quote.

FAQ

How long does a gas furnace last?

Typically 15–25 years, based on industry life-expectancy studies (NAHB and InterNACHI). Your unit's real life depends on how much it runs, maintenance and, for tank water heaters, how hard your water is.

How do I find out how old my furnace is?

The manufacture date is coded into the serial number on the unit's data plate. Each brand writes it differently. Enter the serial in our decoder to get the date, the age, and how much typical life is left.

Is it worth repairing an old gas furnace?

Compare the repair with the cost of replacing. Near the end of its typical life (about 12+ years), a repair over about 30% of replacement cost usually isn't worth it. A new gas furnace typically costs $3,800–$10,000 installed, so that's roughly $2,070.

More guides: How long do water heaters last? · How long do AC units last?

Sources