Repair or Replace? How to Decide on an Aging Furnace or AC
When your furnace or AC acts up, the hardest question isn’t what’s wrong — it’s whether to repair it or replace it. Here’s an honest way to think it through, without the pressure.
The age rule of thumb
- Furnaces typically last 15–20 years.
- Air conditioners typically last 12–15 years.
- Heat pumps typically last 12–15 years.
If your system is comfortably within its expected life, repair is usually the right call. If it’s near or past the end, replacement deserves serious thought — especially before you sink money into a big repair.
The 50% rule
A common guideline: if a repair costs more than 50% of the price of a new system, replacement is often the smarter long-term move. A related version is the “$5,000 rule” — multiply the repair cost by the unit’s age; if the result is over $5,000, lean toward replacing.
These are guidelines, not gospel — but they keep you from pouring money into a system on its last legs.
Efficiency and running costs
An older furnace might run at 70–80% efficiency (AFUE); a modern condensing furnace runs 95%+. An old AC might be SEER 10; a new one can be SEER 16+. On an aging, inefficient system, a chunk of what you’d spend on repairs comes back as lower monthly bills with a new unit.
Rebates change the math
This is the part people miss: Ontario rebates can meaningfully lower the cost of a new, efficient system — especially heat pumps. When you factor rebates in, replacing can be closer to the cost of a major repair than you’d expect. See our rebates guide for what’s available.
Signs it’s time to replace
- Repairs are becoming frequent
- The system struggles to keep up or heats/cools unevenly
- Energy bills keep climbing
- It uses an old or phased-out refrigerant
- A repair quote approaches half the cost of new
The honest answer: get more than one opinion
A single contractor quoting a replacement has an incentive to sell you one. That’s exactly why comparing a couple of quotes matters — it’s how you tell a genuine “replace it” from an upsell. Tell us about your system and we’ll match you with vetted pros so you can compare, with no obligation.