This is one of the biggest decisions an Ottawa homeowner makes, and it’s made worse by the fact that whoever’s quoting you usually makes more money on a replacement than a repair. So let’s lay out the math the way it actually works.
The $5,000 rule
The traditional HVAC rule of thumb is: multiply the furnace’s age (in years) by the repair cost. If that number exceeds $5,000, replace. Under $5,000, repair.
Your 12-year-old furnace needs an $800 repair. 12 × $800 = $9,600. That’s over $5,000, so the rule says replace. Same furnace at 4 years old: 4 × $800 = $3,200. Under $5,000, so repair.
This rule is a decent starting point. But it doesn’t account for efficiency, rebates, or the actual probability of the next repair.
The efficiency math nobody mentions
A 1990s-era 80% AFUE furnace costs about 20% more to operate per year than a modern 96% AFUE condensing unit. For the average Ottawa home heating bill (~$1,800/year), that’s $360 every year you keep the old unit. Over 5 years, that’s $1,800 in operating savings on top of any repair you avoid.
If you’re comparing a $1,800 repair on a 1990s 80% furnace vs $5,500 to install a 96% unit, the real comparison isn’t $1,800 vs $5,500. It’s $1,800 vs ($5,500 − operating savings − rebates).
The 2026 Ontario rebate consideration
This is where the math shifts dramatically for Ottawa homeowners in 2026. The Home Renovation Savings Program plus Enbridge HER+ plus the Greener Homes Loan can stack to over $10,000 if you’re replacing with a heat pump or hybrid system. See our full rebate breakdown.
That changes the comparison again. $1,800 repair vs $5,500 install becomes $1,800 vs ~$2,000 net after rebates. Suddenly replacement makes a lot more sense.
The rebate landscape in 2026 is unusual. A furnace replacement that would have cost $5,500 in 2022 can net out to under $2,500 today with the right stacked rebates. The same decision looks completely different.
When to definitely repair
- The furnace is under 10 years old AND the repair is under $1,500
- The failure is a minor part (igniter, flame sensor, capacitor) under $500
- You’re selling the house within 12 months
- The current unit is high-efficiency (96%+) and the repair restores it to like-new
When to definitely replace
- The furnace is over 18 years old
- The repair quote exceeds 50% of replacement cost
- The heat exchanger is cracked (carbon monoxide risk)
- The furnace has needed multiple repairs in the last 3 years
- You’re eligible for stacked rebates that bring net replacement below the repair cost
The trap to avoid
The biggest mistake Ottawa homeowners make is the panic-replacement: it’s January, the furnace is dead, the salesperson is in your kitchen, and you sign for a $7,500 install before getting a second quote. Whatever you do, get a second quote unless you’re in genuine danger. Reputable HVAC companies will hold their price for 7 days.
What an honest quote looks like
When we quote a replacement, we provide three options: a like-for-like replacement, a high-efficiency upgrade, and a hybrid heat-pump option (if applicable). Each with itemized labour and parts, the AHRI certificate for the equipment, the rebate documentation we’ll file, and the net-after-rebate cost. You take the quote home, sleep on it, and decide without anyone in your kitchen.
The $169+tax diagnostic gets credited toward the install if you go with us. If you go with someone else, you keep the written diagnosis and the quotes.