Furnace Replacement Cost in Ontario (2026): By System Type & Home Size

A new furnace installed in Ontario typically costs $3,500–$10,000+ CAD, with a provincial average around $6,800 before tax and a narrower typical band of $4,000–$6,500 for most straightforward replacements. Single-stage 80% AFUE furnaces run $3,500–$5,500 installed; two-stage 96% AFUE runs $5,000–$7,500; modulating 98% AFUE runs $7,000–$10,000+. Home size, venting changes, and installation complexity move a specific quote within these ranges.

What determines furnace replacement cost in Ontario

Three variables set the price on nearly every furnace quote: efficiency tier, home size (BTU output needed), and installation complexity. Efficiency tier moves the price the most — a jump from single-stage to modulating equipment changes both the equipment and the venting method. Installation complexity is the variable most homeowners underestimate, and the one most worth asking about before you sign anything (see our quote checklist).

Cost data below is compiled from four independent 2026 Ontario contractor and industry cost guides — see Sources — and reviewed quarterly.

Furnace cost by efficiency tier

Across the overall Ontario market, installed furnace cost runs $3,500–$10,000+, with a provincial average around $6,800 before tax. Most straightforward replacements land in a narrower $4,000–$6,500 typical band; the ranges below break that out by efficiency tier.

Single-stage furnaces vent through a metal flue, often reusing an existing chimney liner, which keeps installation simpler and cheaper. Two-stage and modulating condensing furnaces vent through PVC pipe run to an exterior wall, which is a bigger install job the first time a home switches tiers — expect a modest one-time venting cost on top of equipment if this is your first high-efficiency furnace.

Furnace cost by home size

Furnace size is measured in BTUs (British Thermal Units) of heat output. For Ontario’s climate, HRAI (the Heating, Refrigeration and Air Conditioning Institute of Canada) is commonly cited for a sizing rule of thumb of roughly 30–45 BTU per square foot — colder, older, or poorly-insulated homes trend toward 45–50+ BTU/sq ft, while newer, well-insulated homes trend toward 30–35. This is a starting estimate only, not a substitute for a proper load calculation (see below).

Rather than a flat “add $X per extra 500 sq ft,” the more accurate way to think about cost is a tier-shift effect: a larger home needs higher BTU output, which can push the equipment selection into the next efficiency-tier pricing bracket rather than adding a small linear amount within the same bracket. A 2,500 sq ft home, for example, is more likely to need the $5,000–$7,500 two-stage tier than the $3,500–$5,500 single-stage tier — see the tier table above. Most competing cost pages imply linear per-square-foot scaling, which understates the real jump.

Square footage is a starting estimate, not a final answer. True sizing requires a CSA F280-11 load calculation (the Canadian standard equivalent to the U.S. Manual J), which accounts for insulation R-value, window count and type, ceiling height, air leakage, and your local design temperature — not just floor area. A furnace sized by square footage alone can be wrong by 20% or more in either direction. Ask any quoting contractor whether they performed a CSA F280 (or Manual J) load calculation, or sized the replacement “by the old unit” — a common shortcut that just repeats whatever sizing error the original installer made. This is one of the checklist items in our quote evaluation guide.

What pushes a quote above the typical range

• Venting changes — switching from a chimney to PVC sidewall venting for a first-time high-efficiency install: $500–$1,500
• Electrical upgrades — older panels sometimes need a dedicated circuit or panel work: $300–$1,200
• Ductwork modifications — undersized or damaged ducts feeding the new furnace: $500–$3,000+
• Permit and inspection fees — municipal permits in Ontario typically run $200–$500
• Removal and disposal of the old unit — typically $100–$300; usually bundled into quotes but worth confirming it’s included
• Asbestos abatement — homes built before 1990 with old duct wrap or insulation may need professional abatement before work starts, which is a separate line item

Two situations that add a specific, known premium

• Emergency mid-winter replacement — a furnace that fails in the coldest months typically costs 20–50% more than the same job booked in spring or fall, largely because emergency scheduling removes your ability to shop multiple quotes calmly. If your furnace is aging but still working, this is the single best argument for planning the replacement before it fails — see the decision framework in our full decision guide.
• Oil-to-gas conversion — switching a home currently heated with oil to a gas furnace adds roughly $1,500–$3,500 on top of the furnace installation itself, covering the gas line and tank/oil-system decommissioning work. If you’re on oil, also check the Oil to Heat Pump Affordability rebate before committing to a gas conversion — it specifically targets oil-heated homes and can change the math.

Furnace vs. heat pump: a cost note

This guide covers furnace-only replacement cost. If you’re deciding between staying on gas and switching to a heat pump, the upfront cost comparison is only half the picture — operating costs over the system’s life often matter more. See our operating cost comparison and the full decision guide.

How to use this guide when you get quotes

1. Identify which efficiency tier your quotes are for — some contractors quote mid-efficiency by default because it’s cheaper to install, not because it’s right for your home.
2. Confirm the BTU sizing is backed by a load calculation, not eyeballed.
3. Ask which of the “pushes it higher” items above apply to your home specifically, before the crew shows up.
4. Compare at least two quotes for the same efficiency tier and BTU size — see our checklist for the full evaluation process.