# Replacing a gas furnace in Toronto and the GTA

> Replacing a gas furnace in Toronto, Mississauga, Markham or Ajax: which cities need a permit, the typical $4,000 to $7,000 price, and the rules that follow.

- Canonical HTML: https://www.jackmanmechanical.com/guides/replacing-gas-furnace-toronto/
- Section: Home > Guides > Replacing a gas furnace in Toronto and the GTA
- Business: Jackman Mechanical Ltd., Toronto, ON, Canada (serves Toronto, North York, Mississauga, Markham, Ajax)
- Phone: (416) 888-1371 | Text: (289) 639-2754 | Email: jackmanmechanicallimited@gmail.com
- Page updated: 2026-10-21

---

Guide

In Toronto, replacing a furnace in a house takes a stand-alone HVAC permit, $214.79 flat in 2026. Mississauga wants a permit when the new furnace is more efficient than the old one or the ducts change, and Markham does not for a furnace of the same kind. Jackman Mechanical's typical price for a new furnace is $4,000 to $7,000 all in, depending on the size the home needs.

## 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.

**Replacing a furnace in a house: what each city's building department says, read October 2026**

| City | Permit for a furnace replacement? | Source |
| --- | --- | --- |
| [Toronto and North York](https://www.jackmanmechanical.com/areas/toronto/) | Yes. A stand-alone HVAC permit, $214.79 flat for a house in 2026. | [City of Toronto](https://www.toronto.ca/services-payments/building-construction/building-permit/before-you-apply-for-a-building-permit/building-permit-application-guides/standalone-plumbing-mechanical-and-drains/standalone-plumbing-and-drain-permits/) |
| [Mississauga](https://www.jackmanmechanical.com/areas/mississauga/) | Yes when the new furnace is of a higher efficiency than the existing one, or the ducts are altered. The application uses the City's Residential Furnace Replacement Form. | [City of Mississauga](https://www.mississauga.ca/services-and-programs/building-and-renovating/building-permits/when-a-building-permit-is-required/) |
| [Markham](https://www.jackmanmechanical.com/areas/markham/) | Not for a furnace of the same kind. Yes when the fuel changes, for example from electric to natural gas. | [City of Markham](https://www.markham.ca/about-city-markham/city-hall/bylaw/decks-construction-permits) |
| [Ajax](https://www.jackmanmechanical.com/areas/ajax/) | The Town's permit pages do not list furnace replacement on its own. Ask Building Services at buildingpermits@ajax.ca before the work. | [Town of Ajax](https://ajax.ca/life-in-ajax/town-services/construction-permits-inspections/) |

Mississauga's application asks for heat loss calculations and an HVAC drawing when ducts are altered [(City of Mississauga)](https://www.mississauga.ca/services-and-programs/building-and-renovating/building-permits/drawings-and-documents-you-need-for-a-building-permit/furnace-replacement/). 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](https://www.jackmanmechanical.com/guides/plumbing-heating-permits-toronto/).

## 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](https://www.jackmanmechanical.com/faq/#new-furnace-cost), 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](https://www.jackmanmechanical.com/residential/furnaces/) 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)](https://www.tssa.org/repeat-offender-convicted-unlicensed-gas-appliance-work-ontario-homes). The [gas work guide](https://www.jackmanmechanical.com/guides/who-can-work-on-gas-ontario/) 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)](https://www.ontario.ca/page/carbon-monoxide-safety). The [alarm guide](https://www.jackmanmechanical.com/guides/carbon-monoxide-alarms-ontario/) 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)](https://www.enbridgegas.com/ontario/safety/smell-gas). A rotten egg smell means leave the house and call Enbridge Gas at [1-866-763-5427](tel:+18667635427) 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:

**Minimum indoor heat in a rental, by city, read October 2026**

| Where | Minimum | When |
| --- | --- | --- |
| Toronto | 21°C | October 1 to May 15 |
| Mississauga | 20°C | No dates in the by-law |
| Markham | 20°C by day, 16°C at night | No dates on the City's summary |
| Ajax | 20°C | September 15 to May 31 |
| Ontario, everywhere | 20°C | September 1 to June 15 |

Each row's source, and what each city counts, is on the [areas page](https://www.jackmanmechanical.com/areas/). For a building with more than one unit, the [commercial heating page](https://www.jackmanmechanical.com/commercial/heating/) and the [rental heat guide](https://www.jackmanmechanical.com/guides/no-heat-rental-toronto/) 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](https://www.jackmanmechanical.com/guides/door-to-door-water-heater-furnace-ontario/) 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.

## Pricing a new furnace?

Send a photo of the label inside the furnace door and the room it sits in.

[Request a quote](https://www.jackmanmechanical.com/request/?problem=no_heat)

## No heat now?

Call, any hour.

[Call (416) 888-1371](tel:+14168881371)

---

Jackman Mechanical Ltd.: plumbing, gas and heating for homes and businesses in Toronto, North York, Mississauga, Markham and Ajax. Call (416) 888-1371. Full site: https://www.jackmanmechanical.com/