Furnace Replacement: Costs & When to Do It

A furnace replacement is usually a one-day job. This guide covers what it costs by fuel type and efficiency, the signs your furnace is done — including the safety ones — and how to hire well.

What furnace replacement involves

Furnace replacement removes the old unit and sets a new one sized to your home's heating load, then reconnects the gas or electrical supply, the venting, the ductwork, and the thermostat, and runs a combustion analysis at startup. Moving from an 80% to a 90%+ AFUE furnace adds sealed PVC venting and a condensate drain.

If the air conditioner shares the coil and blower and is also aging, replacing both together keeps the system matched and usually costs less than two visits.

Timing

Signs it's time to replace your furnace

Age

Gas furnaces last about 15–20 years. Past that, efficiency drops and parts get scarce.

Cracked heat exchanger

A safety issue that usually costs enough to repair that replacement is the better call.

Repeated repairs

Two or more failures in a couple of years, or a major part like the control board or blower.

Rising heating bills

Fuel use climbing despite maintenance means the furnace has lost efficiency.

Yellow flame or soot

Signs of incomplete combustion — have it inspected, and plan for replacement if the heat exchanger is involved.

Uneven heat / constant running

The furnace can't keep up, is the wrong size, or is nearing the end of its life.

Cost

Typical furnace replacement cost

Installed ranges for a typical home. Tailor it with the Furnace Replacement Cost Calculator.

Furnace typeTypical range
Gas furnace, 80% AFUE$3,000 – $5,500
Gas furnace, 90–96% AFUE$4,500 – $8,000
Propane furnace$3,500 – $7,000
Oil furnace$5,000 – $9,000
Electric furnace$2,500 – $5,000
Venting conversion (80% → 90%+)+$500 – $1,500
Full system (furnace + AC)$8,000 – $16,000

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Safety

The safety case for replacing

Some furnace problems are a reason to replace rather than repair, mostly for safety:

  • A cracked or corroded heat exchanger — a carbon-monoxide risk
  • Persistent soot, a yellow burner flame, or a tripping CO detector
  • Rust or water damage from a failed high-efficiency condensate system
  • A furnace so old that replacement parts are no longer made
  • Repeated safety-lockout faults a technician can't permanently resolve

If you smell gas or a CO detector sounds, leave the home immediately and call 911 or your gas utility from outside. A licensed technician should confirm a heat-exchanger crack before you decide.

Questions to ask before you replace

  • Did you size the furnace with a load calculation?
  • What AFUE are you quoting, and why that level for my climate?
  • Does the price include new venting and a condensate drain if needed?
  • Should the AC be replaced at the same time?
  • Is a permit, combustion analysis, and inspection included?
  • What's the heat-exchanger warranty and the labor warranty?
  • Which rebates or tax credits apply?
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FAQ

Furnace Replacement Questions

How much does furnace replacement cost?

An 80% AFUE gas furnace runs about $3,000–$5,500 installed; a 90–96% model runs $4,500–$8,000. Propane, oil, and electric furnaces fall outside that range. Estimate yours with the Furnace Replacement Cost Calculator.

How do I know if I need a new furnace?

If the furnace is 15+ years old and needs a major repair — heat exchanger, control board, blower — or you’ve had repeated failures, replacement is usually the better value. The Repair or Replace calculator weighs it out.

Is a cracked heat exchanger dangerous?

Yes — it can leak carbon monoxide into your home's air. A technician should confirm the crack, and a furnace with a cracked heat exchanger should be replaced or repaired before use.

Should I switch to a heat pump instead?

In many climates a heat pump replaces both heating and cooling with one efficient system and can qualify for a larger tax credit. Compare with the Heat Pump vs. Furnace + AC calculator.

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