How long do furnaces last in Ontario?
A well-maintained gas furnace in Ontario usually lasts about 15 to 20 years. Oversizing, dirty filters and venting or drain problems shorten that; a correct install and yearly service help it reach the top of the range.
15to20years
Well-maintained, correctly sized gas furnace. A typical range, not a guarantee.
- 0 to 10 yearsEarly yearsFailures are usually one small part or an installation fault, and parts are often still under warranty.
- 10 to 15 yearsMiddle ageIgniters, flame sensors, inducer and blower motors start to wear. Most repairs are still worth doing.
- 15 to 20 yearsTypical end of lifeRepairs get bigger and closer together. Price a replacement before you need one.
- 20 years and upBorrowed timeSome furnaces keep going. Plan the replacement on your schedule, not the furnace’s.
On this page
That range assumes a furnace that was sized and installed properly and serviced most years. Some well-kept furnaces run past 20 years; an oversized or neglected one can fail well before 15. What finally retires a furnace is usually a failed heat exchanger, the steel chamber that keeps flame and exhaust separate from your house air, or a run of repairs that no longer makes sense on an old unit. When that point comes, the Ontario Furnace Prices home page shows what a replacement typically costs, system by system.
Ontario winters add hours. A furnace in Ottawa or Barrie works through a longer, colder season than one in Windsor, but sizing, airflow and maintenance matter more than the city you live in.
What shortens a furnace’s life
Many early failures trace back to heat that cannot get out of the furnace, or water and exhaust that cannot get out of the house.
| Cause | What it does | What to do |
|---|---|---|
| Oversizing | Short, frequent cycles: more starts for the igniter and inducer, more heat stress on the heat exchanger | Size the replacement with a CSA F280 heat loss calculation |
| Dirty filters | Low airflow makes the heat exchanger run hot and trips the high-limit switch | Check monthly in winter; replace every 1 to 3 months |
| Weak duct airflow | Undersized returns or closed vents act like a permanently dirty filter | Keep vents open; ask for a static pressure test |
| Venting problems | Blocked or snow-covered vent pipes cause lockouts and can push exhaust back inside | Keep outdoor pipes clear; have venting checked yearly |
| Condensate problems | On high-efficiency furnaces, a plugged trap or frozen drain shuts the furnace down, and the acidic water corrodes what it touches | Clean the trap and drain yearly; protect lines from freezing |
| Chemicals nearby | Fumes from bleach, solvents and paint strippers drawn into the burner corrode the heat exchanger | Store them away from the furnace |
| Humidifier leaks | Water dripping into the cabinet rusts burners and controls | Service the humidifier each fall |
What helps a furnace last
- A furnace sized to the house, with blower speed and temperature rise set for your ductwork
- Filters checked monthly in winter and changed every 1 to 3 months
- A yearly tune-up, typically $120 to $250: combustion check, flame sensor, igniter, heat exchanger, condensate trap and drain
- Supply and return vents left open and clear of furniture
- Outdoor intake and exhaust pipes kept clear of snow, ice and leaves
- Small faults fixed early: a dirty flame sensor today is cheaper than a lockout on the coldest night
Maintenance will not make an old furnace new, but it catches the faults that end furnaces early. Furnace maintenance cost covers what a tune-up should include.
How to tell how old your furnace is
Find the rating plate
Switch the furnace off at its service switch and remove the front panel. The label inside lists the model and serial number, and many also print a manufacture date.
Decode the serial number with the manufacturer
Most brands encode the build date in the serial number, but formats differ by brand and have changed over the years. Use the manufacturer’s own guidance or customer support, not a generic decoder.
Look at the vent pipe
Canadian rules required at least 90% AFUE, which in practice means a condensing furnace with plastic venting, for most new gas furnaces made from December 31, 2009. A furnace with a single metal vent into a chimney was very likely built before 2010.
Check the paperwork
An invoice, warranty registration, service stickers, your home inspection report or a permit record can all date the install.
Non-condensing (mid-efficiency)
- One metal vent pipe, usually grey or silver
- Rating plate inside the front panel
- Vent runs up into a chimney or metal stack
Most of these were built before 2010, so most are now 16 years old or more.
Condensing (high-efficiency)
- Two plastic pipes (intake and exhaust), usually white or grey
- Rating plate inside the front panel
- Condensate line to a floor drain or pump
The norm for new gas furnaces since December 31, 2009. Use the serial number to pin down the year.
Warning signs a furnace is wearing out
- Age past 15 years. Not a reason to replace on its own, but a reason to start pricing.
- Repairs getting bigger and closer together. Two significant repairs in two winters is a pattern.
- Uneven heat. Rooms that never warm up, or a furnace that runs and runs on cold nights.
- Short cycling. Starting and stopping every few minutes, often from overheating, a sensor fault or oversizing.
- Frequent lockouts. A furnace that only restarts after a power reset is reporting a fault; note the blinking code.
- A yellow, lazy flame or soot around the burners. A healthy gas flame is mostly blue.
- New noises, such as a bang at ignition or squealing from the blower.
- Rising gas bills, or rust and water inside the cabinet.
Carbon monoxide and gas smells: get out first, diagnose later
A worn furnace can leak carbon monoxide (CO), which you cannot see or smell. Ontario’s Fire Code requires a working CO alarm next to every sleeping area in homes with a fuel-burning appliance, a fireplace or an attached garage, and since January 1, 2026, on every storey of the home. If it sounds, get everyone out and call 911 from outside.
If you smell gas, leave without touching light switches or anything that could spark, then call your gas utility’s emergency line or 911 from outside.
If a technician finds an immediate hazard, such as a cracked heat exchanger, they will shut the furnace off and tag it. Do not run a tagged furnace. Ask to see the evidence and get a second opinion from another TSSA-registered contractor before you sign for a replacement.
Repair or replace: the numbers
Most repairs cost a fraction of a new furnace, so the decision comes down to age and what is likely to fail next.
- Igniter
- $250 to $450Wears out at any age
- Inducer motor
- $600 to $1,200Common on older furnaces
- ECM blower motor
- $900 to $1,800Variable-speed blower
- New furnace, installed
- $4,000 to $6,500Single-stage, before HST
| Furnace age | Small repair (under $500) | Major repair ($500 to $1,800) | Cracked heat exchanger |
|---|---|---|---|
| Under 10 years | Repair | Repair; check the parts warranty | Check the warranty; labour may not be covered |
| 10 to 15 years | Repair | Usually repair; get a replacement price too | Usually replace |
| 15 to 20 years | Repair, then plan | Lean toward replacing | Replace |
| Over 20 years | Repair only to buy time | Replace | Replace |
A guide, not a rule. Safety, comfort and how long you plan to stay can tip it either way. Repair prices are typical Ontario ranges before HST.
A heuristic some technicians use: multiply the furnace’s age by the repair price, and above about $5,000, lean toward replacing. A 12-year-old furnace needing a $350 igniter scores $4,200: repair it. A 16-year-old needing a $900 inducer motor scores $14,400: start pricing replacements. Treat it as a prompt, not a verdict. The repair or replace check also weighs repair history and your plans, and the furnace repair cost guide prices every common part.
Find out what replacing yours would cost
A free in-home estimate gives you a written replacement price to weigh against the repair, with no obligation to buy.
Free, no obligation. About a minute to request.
Replace on your schedule, not the furnace’s
The most expensive furnace is the one you replace in a January emergency, taking the first available install and skipping the comparison. If yours is past 15 years, use spring or early fall to get two or three quotes, ask for a heat loss calculation and decide whether a heat pump or dual fuel system makes sense.
If you replace: typical installed prices
Heating$4,000to$11,000
Typical installed price, Ontario 2026, all options shown
- Gas furnace, single-stage95 to 96% AFUE $4,000 to $6,500
- Gas furnace, two-stage96% AFUE, ECM blower $5,500 to $8,000
- Gas furnace, modulating97 to 98% AFUE, variable speed $7,000 to $11,000
Installed price in Ontario, before 13% HST ($4,520 to $12,430 with HST). Standard replacement in a detached home with usable ductwork and venting.
See furnace prices in Ontario for what moves those numbers, the furnace buying guide for the decisions in order, and the best time to buy a furnace for timing.
Questions people ask
Can a furnace last 30 years?
Some do, but it is not something to plan around. A 30-year-old furnace is far less efficient than a new 95% model, parts can be hard to find, and the heat exchanger has been through decades of heating and cooling. If yours is that old, have it inspected each fall and price a replacement now.
Should I replace a 20-year-old furnace that still works?
Not automatically. If it passes a safety inspection and heats the house evenly, keep running it while you plan. What you gain by replacing early is choice: time to compare quotes, size the new furnace properly and consider a heat pump, instead of taking the first install available in a cold snap.
Do high-efficiency furnaces last as long as older ones?
A well-installed condensing furnace can reach the same 15 to 20 year range. It has more parts that need care, including a second heat exchanger, a condensate trap and drain and plastic venting, so skipped maintenance shows up sooner. Many early failures trace back to installation, airflow or drainage rather than the design.
Does the warranty tell me how long my furnace will last?
No. A warranty is a promise to supply certain parts for a period, not a prediction of life. Heat exchanger coverage often runs longer than other parts, and labour is usually separate and shorter. Keep the registration confirmation, because a covered part can still leave you paying for the labour.
Do furnaces wear out faster in colder parts of Ontario?
A furnace in Ottawa, Barrie or Sudbury runs more hours each winter than one in Windsor or Niagara, so wear builds a little faster. In practice, sizing, airflow, venting and maintenance have a bigger effect than climate. A right-sized, serviced furnace in a cold city can outlast a neglected one in a mild one.