Furnace Repair vs Replace: When to Fix and When to Buy New
A simple decision framework with real numbers. The 50% rule, age-based guidance, and common repair costs to help you make the right call.
The 50% Rule
If the repair costs more than 50% of a new furnace, replace it.
A new gas furnace averages $5,500 installed. If your repair quote is over $2,750, you are better off putting that money toward a new unit with a fresh warranty, better efficiency, and 15 to 20 years of reliable service ahead of it.
Decision Matrix by Age
| Furnace Age | Recommendation | Repair Budget |
|---|---|---|
| Under 10 years | Almost always repair | Up to $1,500 (unless heat exchanger) |
| 10 - 15 years | Repair if reasonable, start planning | Up to $1,000; replace if major component |
| 15 - 20 years | Lean toward replacement | Up to $500 for minor fixes only |
| 20+ years | Replace (unless trivial repair) | Under $300 for simple fixes; otherwise replace |
Common Furnace Repairs and Costs
| Repair | Cost | Repair or Replace? |
|---|---|---|
| Flame sensor cleaning/replacement | $100 - $200 | Always repair |
| Thermocouple replacement | $100 - $250 | Always repair |
| Ignitor replacement | $150 - $300 | Always repair |
| Draft inducer motor | $250 - $500 | Repair if under 15 years |
| Circuit board replacement | $300 - $600 | Repair if under 12 years |
| Blower motor replacement | $400 - $800 | Repair if under 12 years |
| Gas valve replacement | $400 - $800 | Consider age carefully |
| Heat exchanger replacement | $1,500 - $3,000 | Usually replace the furnace |
Signs It Is Time to Replace
Age 15+ years
Gas furnaces are designed for a 15 to 20 year lifespan. Beyond 15, the risk of major component failure increases each year.
Frequent repairs (2+ per season)
If you are spending $500+ per year on repairs, that money is better invested in a new unit.
Cracked heat exchanger
The most serious and expensive repair. A cracked heat exchanger can leak carbon monoxide. Replacement cost ($1,500 to $3,000) usually makes a new furnace more economical.
Rising gas bills
A furnace losing efficiency over time means your gas bills climb even when rates stay flat. A new 96% AFUE furnace can cut heating costs 20% compared to an aging 80% unit.
Yellow or flickering burner flame
A healthy gas furnace has a steady blue flame. Yellow indicates incomplete combustion, which reduces efficiency and can produce carbon monoxide.
Excessive dust and dry air
Old furnaces with worn-out blower motors and poor filtration contribute to dusty, dry indoor air that modern variable-speed units handle much better.
Efficiency Gains from Replacement
Replacing an 80% AFUE furnace with a 96% AFUE
In cold climates where annual gas bills are $1,500 to $2,000, savings increase to $250 to $333 per year.
Use our payback calculator to see your specific savings.
Warranty Considerations
Warranty status is a major factor in the repair vs replace decision.
In Warranty
Parts are covered (you pay labour only, typically $200 to $500). Almost always worth repairing unless the furnace has other serious issues.
Out of Warranty
You pay full parts + labour. A blower motor repair goes from $200 (labour only) to $400 to $800 (parts + labour). Apply the 50% rule and age matrix more aggressively.