A forced-air gas furnace typically lasts about 15–20 years, central air conditioning about 12–15, 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.
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
Roughly $4,000–8,000 to replace a furnace with a high-efficiency model installed, $4,000–7,000 for central AC, and around $8,000–12,000 to do both. A cold-climate heat pump runs $6,000–15,000+ but is often offset by federal and provincial rebates. Prices vary with home size, ductwork, and access.
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 Aging furnace & HVAC?
A forced-air gas furnace typically lasts about 15–20 years, central air conditioning about 12–15, 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.
Why does it matter for home buyers?
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 can I 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.
How much does it cost to fix?
Roughly $4,000–8,000 to replace a furnace with a high-efficiency model installed, $4,000–7,000 for central AC, and around $8,000–12,000 to do both. A cold-climate heat pump runs $6,000–15,000+ but is often offset by federal and provincial rebates. Prices vary with home size, ductwork, and access.
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 2026-06-29.
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.