5 Signs Your Furnace Is Dying (And What Replacement Costs in 2026)

Furnaces do not usually fail without warning. There are almost always signs in the weeks or months beforehand — signs that are easy to ignore when the house is still getting warm. Catching them early saves you from a midnight breakdown in January when every HVAC company in Ontario is slammed and emergency rates apply. Here are the five signs that your furnace is on its way out.

1. Your Furnace Is 15 Years Old or More

The average gas furnace lasts 15 to 20 years with proper maintenance, and 12 to 15 years without it. If your furnace is pushing 15 and you are reading this article, you are probably already sensing that something is off. Age alone is not a death sentence — some well-maintained furnaces run 25 years. But after 15 years, the odds of a major component failure increase sharply every season.

Check the serial number on your furnace's rating plate to find the manufacture date. The first two or four digits usually encode the year. If you cannot decode it, your technician can tell you during a service call.

A furnace manufactured in 2010 or earlier is also running at a lower efficiency rating than anything available today. Even if it is not broken, it is costing you more to heat your home every month than a modern unit would. An older 80% AFUE furnace wastes 20 cents of every dollar you spend on gas. A modern 96% AFUE unit wastes four cents.

2. You Are Calling for Repairs More Than Once Per Season

One repair call per heating season is normal for an older furnace. A flame sensor fails, a blower motor capacitor dies, an ignitor cracks — these are wear items and replacing them is routine. But if you have had two or more repair calls in a single winter, or you have been calling for repairs every year for the past few years, the pattern is telling you something.

Add up your furnace repair costs over the last three years. If the total exceeds 50% of the cost of a new furnace, replacement makes more financial sense. This is the "50% rule" — simple, practical, and widely used by honest contractors.

A common scenario: the blower motor fails ($400-$700 repair), and six months later the control board goes ($500-$900 repair). You have now spent $900-$1,600 on a furnace that is still old and could have another failure next month. That money would have been better applied toward a new unit.

3. Uneven Heating Throughout Your Home

If some rooms are warm while others are noticeably cold, and this is a change from how the furnace used to perform, the furnace is likely losing its ability to distribute heat effectively. Common causes include:

Failing blower motor: Not pushing enough air through the ductwork to reach distant rooms
Cracked heat exchanger: Reduced heat transfer efficiency
Undersized system: If your furnace was always marginally sized for your home, declining performance with age makes the problem obvious

Note: uneven heating can also be caused by ductwork problems (disconnected or leaking ducts, blocked vents). A technician should inspect both the furnace and the ductwork to identify the real cause.

4. Your Gas Bill Is Climbing Despite Steady Usage

If your gas bill has been creeping up over the past few winters and you have not changed your thermostat habits or added living space, your furnace is losing efficiency. As components wear — burners get dirty, heat exchangers develop micro-cracks, blower motors slow down — the furnace has to burn more gas to produce the same amount of heat.

Compare your gas consumption (in cubic metres, not dollars — rates change) year over year. Enbridge bills show this breakdown. If consumption is up 15-20% or more with no other explanation, the furnace is the likely culprit.

A furnace that was 92% efficient when new might be operating at 80% or lower after 15 years of wear. That 12% efficiency loss on a $1,500/year gas bill is $180/year — and it gets worse every season.

5. Strange Smells or Unusual Noises

Trust your senses on this one.

Smells

Rotten egg / sulphur smell: This is a gas leak. Shut off the furnace, leave the house, and call Enbridge (1-866-763-5427) and your HVAC company immediately. This is a safety emergency.
Burning dust smell (first startup of the season): Normal — dust accumulated in the ducts and on the heat exchanger burns off in the first few hours. If it persists beyond a day, call for service.
Metallic or electrical burning smell: Overheating components. Shut the furnace off and call for repair.
Musty or mouldy smell: Moisture problem in the system, possibly a condensate drain issue on a high-efficiency furnace.

Noises

Banging or popping: Delayed ignition (gas builds up before igniting) or expanding/contracting ductwork. Delayed ignition is dangerous and needs immediate attention.
Squealing or screeching: Blower motor bearing failure or belt slippage. The motor is dying.
Rattling: Loose panels, failing motor mount, or a cracked heat exchanger.
Constant humming: Blower motor running continuously or a failing inducer motor.

Any new noise that was not there last season is worth investigating. Furnaces get louder as they age, and the noises usually correspond to specific component failures.

What a New Furnace Costs in Ontario (2026)

If you are seeing multiple signs from the list above, here is what replacement looks like financially:

Standard efficiency (80% AFUE): $3,500 - $4,500 installed
Mid-efficiency (92-95% AFUE): $4,500 - $6,500 installed — this is what most Ontario homeowners choose
High efficiency (96-98% AFUE): $6,000 - $8,500 installed

These prices include the furnace, standard installation, permits, and a basic thermostat. Add $300-$800 for venting changes if you are upgrading from an 80% to a high-efficiency unit, and more if ductwork modifications are needed.

Ontario rebates from Enbridge and the Home Renovation Savings Program can reduce the cost by $500-$1,800. See our full furnace pricing guide for detailed breakdowns by efficiency tier.

Repair vs. Replace: The Decision Framework

Under 10 years old, single issue, repair under $600: Repair it.
10-15 years old, repair $600-$1,200: Weigh the repair cost against the age. If you have had other repairs recently, lean toward replacement.
15+ years old, any significant repair: Replace. The repair buys you months, not years.
Cracked heat exchanger, any age: Replace the furnace. This is a carbon monoxide safety hazard and the repair cost approaches the price of a new unit.

Do Not Wait for the Emergency

The best time to replace a furnace is when you choose to, not when it forces you to. Emergency replacements cost more (overtime labour, expedited shipping), give you fewer equipment options (whatever is in stock), and happen when every HVAC company is booked solid.

If your furnace is showing any of these signs, call Relica Comforts for an honest assessment. We serve Barrie, Innisfil, and communities across the GTA. We will inspect your furnace and tell you straight — repair it or replace it. No pressure either way. Furnace installation with upfront pricing, licensed technicians, and a full warranty. Call (647) 491-6009 or book online.