Replace or Wait

Old Furnace Warning Signs: Replace Before January or Wait?

Age alone does not settle it. A furnace can work reliably for 15 to 20 years and often longer, so the real question is what yours is doing. This guide covers the signs that matter, the safety red flags, and how to decide before the cold arrives.

By the Megacity HVAC teamPublished September 21, 2026

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Quick Answer: Replace or Wait?

Replace before January if the furnace has a safety problem, or if it is in the 15 to 20 year range and repairs keep coming. Wait if it is running well and a tune-up finds nothing serious. The cheapest way to know which you are is a fall inspection by a gas technician, which is $120 to $180 with us.

Age range from Hydro One; efficiency rule from Natural Resources Canada. Both checked September 21, 2026.

Age

How Old Is Too Old

Hydro One puts it this way: a furnace “can work reliably for 15 to 20 years,” and likely more if it is properly maintained (Hydro One). To find your furnace's age, look for the rating plate inside the cabinet. It carries the model and serial number, and the build date can usually be decoded from the serial number.

Age also tells you about efficiency. Natural Resources Canada requires gas furnaces made on or after July 3, 2019 to be at least 95% AFUE, with exceptions such as replacement non-condensing units (NRCan). Its older guide lists mid-efficiency furnaces at 78 to 84% and condensing furnaces at 90 to 98%, and estimates that replacing a 20-year-old 78% furnace with a 95% one cuts annual energy cost by about 18% (NRCan, Heating with Gas). Your savings depend on your house and your gas use.

The Signs

Warning Signs, Sorted by Urgency

Safety signs: stop and call

A carbon monoxide alarm goes off. Leave the house and call 911. Do not look for the cause (Health Canada).
You smell gas. Leave, call 911, then Enbridge at 1-866-763-5427.
The flame is yellow, orange or flickering instead of steady blue, or there is soot or rust around the cabinet.
A technician finds a cracked heat exchanger. That is a safety problem, and it usually ends the repair conversation.

Performance signs: plan a replacement

Repeated repair calls in one or two seasons.
The furnace cycles on and off in short bursts, or takes several tries to start.
Banging, squealing or rattling that is new.
Rooms that heat unevenly, or a house that cannot hold temperature the way it used to.
Gas bills climbing when your rate and the weather have not.

One of these on a young furnace is a repair. Several on a furnace past 15 years is a pattern. If it will not start at all, our furnace not working checklist covers what to try before you call, and furnace repair in Toronto is the next step.

The Decision

Replace Before January, or Wait

Replace this fall if

There is any safety finding: a cracked heat exchanger, a venting problem, or a carbon monoxide reading you cannot explain.
The furnace is in the 15 to 20 year range or older and you have had repeated repairs.
You are already looking at a large repair on old equipment.

Wait, with a plan, if

It heats evenly, starts on the first try and passed a tune-up with no safety findings.
You want to budget or line up financing before you buy.

If you wait, know what you are risking: a furnace that quits in a cold snap means replacing on the day it fails instead of on a day you chose. Spring and early fall are usually easier for pricing and scheduling; see the best time to buy a furnace. The safest middle path is to book the inspection now and decide with the written report in hand.

Also check your alarms. Since January 1, 2026, Ontario requires a working carbon monoxide alarm on every storey of a home with a fuel-burning appliance, a fireplace or an attached garage, plus one next to each sleeping area (Ontario.ca).

Paying for It

Cost, Lease-to-Own and Rebates

New furnace installations start from $3,500 in Toronto; the price depends on the size, the efficiency and the work your house needs. Our furnace replacement page has the details, and the estimate is free.

If you would rather not pay up front, we offer $0-down lease-to-own through Enbridge Sustain for approved residential customers, with maintenance and repairs included for the term under Sustain's published terms. We do not rent furnaces. Rent, lease-to-own or buy compares the three, and financing has the options.

On rebates, be careful what you read online. Ontario's Home Renovation Savings program has no rebate for a gas furnace. For a home heated with gas, it offers up to $2,000 for a cold-climate air-source heat pump, and a furnace kept as backup is not covered (Home Renovation Savings). In-house rebates are available with us, so ask at your quote. We do not file government rebate paperwork. If you are weighing a heat pump, start with heat pump vs furnace.

Sources: Hydro One, Natural Resources Canada, Health Canada, Ontario.ca, Home Renovation Savings. Pricing from megacityhvac.com/furnace-replacement-toronto. All checked September 21, 2026. Program amounts change, so confirm on the program site.

Common Questions

Old Furnace FAQs

How long does a gas furnace last?

Hydro One says a furnace can work reliably for 15 to 20 years, and likely more if it is properly maintained. That is a range, not a deadline. A 12-year-old furnace with a cracked heat exchanger needs replacing; a 22-year-old one that passes its inspection may have another winter or two.

Does a new furnace have to be 95% efficient?

In most cases, yes. Natural Resources Canada requires gas furnaces made on or after July 3, 2019 to be at least 95% AFUE. There are exceptions, including replacement non-condensing units and relocatable buildings, so the right unit depends on your venting. We confirm that at the estimate.

Do I need a carbon monoxide alarm on every floor?

If your home has a fuel-burning appliance such as a gas furnace, a fireplace or an attached garage, Ontario now requires a working alarm on every storey, including storeys without bedrooms, plus one adjacent to each sleeping area. The every-storey rule started January 1, 2026.

Is there a government rebate for a new gas furnace?

No. Ontario's Home Renovation Savings program has no rebate for a gas furnace. It covers heat pumps, among other upgrades. In-house rebates are available with us, so ask at your quote. We do not file government rebate paperwork, and homeowners apply to those programs directly.

Should I wait until spring to replace an old furnace?

Only if it is safe and still heating. If the furnace passes a tune-up with no safety findings, waiting for spring is a reasonable call. If it has a safety problem or is failing, waiting means risking a no-heat night in January, and a replacement you did not choose the timing of.

Get a Straight Answer on Your Furnace

We will inspect it, show you what we find in writing, and price a replacement only if you need one. Serving Toronto and the GTA.

(416) 286-5665 Furnace Replacement