Replacing a gas furnace in Toronto and the GTA

Do I need a permit to replace a furnace?

It depends on the city, and the four cities Jackman Mechanical works in answer it four different ways.

Mississauga's application asks for heat loss calculations and an HVAC drawing when ducts are altered (City of Mississauga). A heat loss calculation is how much heat the house loses on a cold day, and it is what a furnace's size is chosen from. Toronto's full fee list, including a furnace replacement in a building other than a house, is in the Toronto permits guide.

How much does a new furnace cost in Toronto?

Jackman Mechanical's typical price is $4,000 to $7,000 all in. What moves it is the size of the furnace your home needs. A repair, when one is possible, is typically $450 to $1,500, depending on the repair. Both are ranges from Jackman Mechanical's own answers on the common questions page, not a quote: each job is priced directly with you, and a quoted job comes with a written estimate before the work starts.

Should I repair or replace my furnace?

It depends on what is wrong with it, so have a technician diagnose the problem before you decide. A furnace that will not start may only have its disconnect switch off, the switch that looks like a light switch on or near the furnace. One that turns on and off over and over is short cycling: it detects a failure, shuts itself off and tries again, and the failure it keeps detecting is what the technician finds. The furnace page has the rest of Jackman Mechanical's answers.

Is a heat pump better than a gas furnace for a Toronto home?

No, in Jackman Mechanical's view. A heat pump still needs a backup heat source for a Toronto winter, so it does not replace the furnace on its own. Adding one to an existing system does not need a permit in Markham, by the City's own guide; in Toronto and Mississauga, ask the building department first.

Who may install a gas furnace in Ontario?

A gas technician certified by the TSSA, Ontario's fuels safety regulator, working for a TSSA-registered contractor. The TSSA says maintenance of furnaces and fuel-fired appliances must be performed by registered contractors, who must hire certified gas technicians (TSSA). The gas work guide shows how to check a company in the TSSA's lookup before you hire it.

What has to be in place once the new furnace runs?

• Carbon monoxide alarms. A home with a fuel-burning appliance needs a working alarm beside each sleeping area and, since January 1, 2026, on every storey (Government of Ontario). The alarm guide has the details.
• A yearly service. Jackman Mechanical's advice is once a year, and the Government of Ontario asks owners to have fuel-burning appliances, chimneys and vents cleaned and inspected by professionals every year (same source).
• Knowing a gas smell from carbon monoxide. Enbridge Gas notes that a carbon monoxide alarm detects carbon monoxide, not a natural gas leak (Enbridge Gas). A rotten egg smell means leave the house and call Enbridge Gas at 1-866-763-5427 or 911 from outside.

When should a landlord replace a furnace?

Outside the months the rental heat rules apply, when that is possible. The minimum differs by city, and in Mississauga it has no season at all:

Each row's source, and what each city counts, is on the areas page. For a building with more than one unit, the commercial heating page and the rental heat guide cover the rest.

Someone offered me a new furnace at my door. Is that allowed?

In Ontario, generally not. Since March 1, 2018, furnaces are one of the products a business may not sell at your home unless you contacted it first and invited it to make a contract. The door-to-door rules guide explains what happens to a contract signed that way.

Published by Jackman Mechanical Ltd., Toronto. Updated October 21, 2026. Free to share and quote, with a link back to this page.