A forced-air gas furnace typically lasts about 15 to 25 years, central air conditioning about 10 to 15, and hot-water boilers often longer. Past those ranges, efficiency falls and the odds of a failure climb. The expensive, safety-relevant failures are a cracked heat exchanger on a furnace (a carbon-monoxide risk) and a dead compressor on an AC. An old "mid-efficiency" furnace also simply costs more to run than a modern high-efficiency condensing unit.
$3,500 to $8,500 furnace installed (high-efficiency $5,500 to $10,500); rebates up to $3,500Address soonHeating
The quick answer
A gas furnace lasts about 15 to 25 years and central AC 10 to 15; past that, efficiency falls and failures climb, usually at the worst moment. The costly, safety-relevant one is a cracked heat exchanger (a carbon-monoxide risk). Replacing a furnace runs about $3,500 to $8,500, central AC $4,500 to $9,000, a heat pump $8,000 to $20,000 (often with rebates). Read the date on the data plate and factor remaining life into your offer.
You are reading the aging furnace & HVAC page. Type the year the house was built and I will tell you what else tends to be true at that age, what it costs, and what to ask. One number, ten seconds.
Free. No account. Educational and impartial, not a home inspection.
Why it matters
Replacing heating or cooling is one of the larger predictable costs in a home, and it tends to come due at the worst moment, a furnace usually fails in a cold snap. Age and efficiency drive your comfort and energy bills, and a cracked heat exchanger is a genuine safety issue. Knowing roughly how many years are left changes both your offer and your first-winter budget.
How to spot it
Read the manufacture date on the data plate of the furnace and the AC condenser; rust or soot around the furnace, short-cycling, uneven heat, or a loud, struggling AC point to age. A mid-efficiency furnace that vents up a chimney (rather than out a white PVC pipe) is usually older. Ask for service records and the age of each unit.
What it costs
Ontario installed pricing: a standard-efficiency gas furnace $3,500 to $8,500 (high-efficiency 96%+ $5,500 to $10,500, most homeowners pay $4,500 to $6,500); central AC $4,500 to $9,000; a cold-climate heat pump $8,000 to $20,000 before rebates, Ontario's Home Renovation Savings program currently offers up to $7,500 for qualifying heat pumps and up to $3,500 for 96%+ furnaces.
What to do
Address soon. Get the documented age of the furnace and AC, budget for replacement based on remaining life, and factor it into your offer. An HVAC technician confirms condition and checks the heat exchanger for cracks. If you're replacing anyway, look at heat-pump rebates before you decide.
Education and triage, not a home inspection. Casaroo estimates equipment age from the unit's photos and data plate, an HVAC technician confirms its true condition and safety. We flag; we don't inspect.
Common questions
What is a cracked heat exchanger and why does everyone mention it?
It is a crack in the metal chamber that separates combustion gases from the air blown through your house, and it can let carbon monoxide into the living space. It is the one furnace failure that is a safety issue rather than a comfort issue, and only an HVAC technician can check for it.
How old is too old?
A gas furnace typically lasts fifteen to twenty-five years. Past that, you are on borrowed time, and a furnace usually fails in a cold snap when contractors are busiest. Get the documented age off the data plate and price $3,500 to $8,500 into your thinking.
Should I replace an old furnace with a heat pump?
It is worth pricing before you default to a like-for-like swap. A cold-climate heat pump runs $8,000 to $20,000 before rebates and Ontario rebates can be substantial, but rebates change, so confirm what is currently available rather than what was available last year.
Is furnace age a fair thing to negotiate on?
Yes, and it is one of the cleanest, because the manufacture date is printed on the unit. You are not arguing about condition, you are pointing at a date.
Lifespans are estimates that vary with maintenance and install quality; rebate programs change. Confirm current offers and have an HVAC technician verify condition. Casaroo flags, it does not inspect.
Last reviewed 2026-07-10.
This guide is general education, not a home inspection and not advice for your specific property. Always
consult the appropriate licensed professional, and get a licensed home inspection before you remove conditions
or buy. Cost ranges are 2026 estimates that vary by region, size, and access; confirm specifics with a
qualified professional.