Should I repair or replace my furnace?
Ben Amina
Aire One East Heating & Cooling, Whitby, Ontario
The question "should I repair or replace my furnace?" comes down to three things: the age of the unit, the cost of the repair against a new furnace, and whether the fault is a safety issue. This guide gives Durham Region homeowners a clear way to decide, including the rule of thumb the trades actually use, an honest cost comparison, and the one exception that overrides everything else. For local service either way, see our furnace repair service.
The short answer: repair the furnace if it is under about 15 years old, running efficiently, and the repair costs a small share of a new unit. Replace it if it is past 15 years, if repairs are stacking up toward the cost of a new furnace, or at any age if the heat exchanger is cracked, which is a carbon monoxide safety issue rather than a comfort one. Age plus repair cost decides most cases; safety overrides both.
Aire One East is a Carrier Factory Authorized dealer serving Durham Region since 1991, with TSSA certified technicians, Licence #1219734, a 4.8 star rating across 364 Google reviews, and 24/7 service. For an honest diagnosis, call 905-576-7600 or book online.
7 signs it is time to replace
Be fair first: none of these alone forces a replacement, but the more that are true, the stronger the case. Lean toward a new furnace when you see several of these.
- Age past about 15 years, the point where efficiency drops and major parts start to fail.
- Repairs stacking up, with the running total approaching a meaningful share of a new unit.
- Rising heating bills from an older furnace below 90 percent efficiency.
- Uneven heating the system cannot correct, often a sizing or wear issue.
- Frequent short cycling that maintenance does not resolve.
- A yellow burner flame or soot, signs of combustion problems worth a prompt inspection.
- A cracked heat exchanger, the one sign that means replace regardless of age, for safety.
When repair is the better choice
Replacement is not always the answer, and a good contractor will tell you so. If your furnace is under 15 years old, running well, and the fault is a common wear part such as an igniter, flame sensor, or a single motor, a repair is almost always the better value. A one-off repair of a few hundred dollars on a furnace with years of life left is money well spent, not a reason to replace. Regular maintenance keeps a healthy furnace in the repair column longer. Our furnace repair in Oshawa and service across Durham cover exactly these fixes.
Repair versus replacement cost
The clearest way to decide is to compare the repair cost against a new furnace. These are typical Durham ranges, verified July 2026, and your quote depends on the specific fault and home.
| Option | Typical Durham cost (CAD) | Makes sense when |
|---|---|---|
| Common repair (igniter, sensor, motor) | $100 to $700 CAD | Furnace under 15 years, otherwise healthy |
| Major repair (control board, gas valve) | $400 to $700 CAD | Newer unit; weigh against age |
| New furnace, installed | $4,500 to $8,500 CAD | Past 15 years, or repairs adding up |
Typical Durham ranges in Canadian dollars (CAD), verified July 2026, subject to change. A common rule of thumb: if a repair costs more than about half a new furnace and the unit is over 15 years old, replace it.
The cracked heat exchanger exception
One fault overrides age and cost. The heat exchanger is the metal wall that keeps combustion gases separate from the air you breathe, and a crack in it can let carbon monoxide into your home. That makes it a safety issue, not a comfort one, and it almost always means replacing the furnace rather than repairing it. Carbon monoxide is colourless and odourless, so detectors on every level are essential, and any headaches or nausea that ease when you leave the house should be treated seriously.
Efficiency, heat pumps, and 2026 rebates
If you are replacing anyway, it is worth asking whether a high-efficiency furnace, or a heat pump paired with a gas furnace, is the better long-term choice. Most Ontario incentives in 2026 favour heat pumps rather than straight furnace swaps, delivered through the Home Renovation Savings Program from Enbridge Gas and Save on Energy. The older Canada Greener Homes Grant closed to new applicants in February 2024, so do not count on it. A dual fuel system, a heat pump above the changeover point with a gas furnace below it, is worth discussing during a replacement, since you are already spending on equipment.
[VERIFY REBATE: confirm current Home Renovation Savings measures and amounts at homerenovationsavings.ca on the day of publish. Do not publish a figure that has not been checked.]
How to decide
- Under 15 years, small repair, no safety issue: repair, and keep up with maintenance.
- Over 15 years, or repairs approaching half a new unit: replace, and consider efficiency gains and rebates.
- Cracked heat exchanger at any age: replace, for safety.
- Rising bills on an old low-efficiency furnace: price a replacement, since the savings may pay part of it back.
- Unsure: get a licensed technician to confirm the heat exchanger and the true repair cost before deciding.
Whichever way you lean, book a furnace replacement quote or a repair diagnosis so the decision is based on your actual furnace, not a guess.
Our licensed technicians confirm the heat exchanger and the real repair cost, then tell you honestly whether to repair or replace. Serving all of Durham Region.
Frequently asked questions
Should I repair or replace my furnace?
Repair if the furnace is under about 15 years old, running well, and the repair is a small share of a new unit. Replace if it is past 15 years, if repairs are stacking up, or at any age if the heat exchanger is cracked, which is a safety issue. A licensed technician can confirm the heat exchanger and the true repair cost before you decide.
At what age should a furnace be replaced?
Most gas furnaces last about 15 to 20 years. Past 15, efficiency has usually dropped and major parts begin to fail, so replacement often makes more sense than a large repair. A well-maintained furnace can run longer, but age is the first thing to weigh.
Is it worth repairing a 20-year-old furnace?
Usually not, for anything beyond a minor fix. At 20 years a furnace is near the end of its life and running at lower efficiency, so a major repair is often money better spent toward a new, more efficient unit. A small repair to get through a season can still make sense if you plan the replacement.
How do I know if my heat exchanger is cracked?
You cannot confirm it yourself; it takes a licensed technician's inspection. Warning signs include a carbon monoxide alarm, soot near the furnace, a yellow flickering flame, and headaches or nausea that ease when you leave the house. Treat any of these as urgent and stop using the furnace until it is checked.
Does a new furnace save enough to justify the cost?
It depends on your current furnace and bills. Moving from an old low-efficiency unit to a high-efficiency one can cut heating costs meaningfully, and rebates can offset part of the price, but the payback varies by home. Ask for the honest numbers for your situation rather than a generic promise.
The bottom line for Durham homeowners
Whether you repair or replace your furnace comes down to age, repair cost against a new unit, and safety, with a cracked heat exchanger overriding everything. Under 15 years with a small repair, fix it. Past 15 or with repairs adding up, price a replacement. When in doubt, get a licensed diagnosis. Call Aire One East at 905-576-7600 or book online.
Related reading
- Furnace replacement cost and process in Whitby
- Furnace repair in Oshawa
- Emergency furnace repair in Ajax
- How to choose the best HVAC company in Durham Region
Sources and references
- Technical Standards and Safety Authority (TSSA), Ontario fuels safety
- ENERGY STAR Canada, Natural Resources Canada
- Health Canada, carbon monoxide and indoor air
Pricing and program details verified July 2026 and subject to change.
