Homeowner Questions · Costs and decisions
Repair or replace: when is a furnace not worth fixing?
A furnace is usually nearing replacement when it is 15 to 20 years old, needs a major repair, has repeated breakdowns, or has a safety problem such as a compromised heat exchanger. One useful check is repair cost multiplied by age: the closer that figure gets to the cost of a new system, the weaker the repair case becomes.
Checked October 26, 2026 · Educational guide, not a quote.
Quick answer
A furnace is usually nearing replacement when it is 15 to 20 years old, needs a major repair, has repeated breakdowns, or has a safety problem such as a compromised heat exchanger. One useful check is repair cost multiplied by age: the closer that figure gets to the cost of a new system, the weaker the repair case becomes.
The short version
- Age 15 to 20 is the common decision zone.
- Safety defects override repair economics.
- Repeated failures matter more than one small repair.
- Price the full replacement while the old system still runs, if possible.
Safety comes before math
A cracked or compromised heat exchanger, carbon monoxide concern, or unsafe venting is not a normal budgeting decision. Shut the equipment down as directed by a qualified technician and deal with the safety issue first.
Look at the pattern, not one invoice
A modest control or ignitor repair on a younger furnace may be sensible. A blower motor, control board or inducer on an older unit can be the first of several failures. Ask what else is worn and whether parts are still readily available.
Replacement can change the whole heating plan
If the air conditioner is also old, or the home heats with oil or propane, replacing only the furnace may lock in another decade of high fuel costs. Compare a furnace-only repair with a full heat pump switch and confirmed rebates before deciding.
What to do next
Get the diagnosis and repair quote in writing.
Ask the technician what is likely to fail next.
Compare repair with a complete replacement and rebate scenario.
Read the full guide
This answer connects to Furnace Died? What To Do This Week, where the full topic is covered with the current Ontario figures and the next checker.
Price the replacement before another major repair
Age, safety and the next likely failure matter as much as today's repair bill.
See the emergency guideQuestions people also ask
Repair or replace: when is a furnace not worth fixing?
A furnace is usually nearing replacement when it is 15 to 20 years old, needs a major repair, has repeated breakdowns, or has a safety problem such as a compromised heat exchanger. One useful check is repair cost multiplied by age: the closer that figure gets to the cost of a new system, the weaker the repair case becomes.
Is the 50 percent repair rule useful?
As a rough guide only. If a repair approaches half the cost of replacement on an older furnace, replacement usually deserves the stronger look.
Should I replace a working furnace just for a rebate?
Not automatically. Remaining life, fuel savings, cooling condition and the cost of waiting for an emergency all belong in the decision.