Calculator
Heat pump sizing estimate
Last reviewed November 2, 2026
How we review content
Your details
Above grade plus a heated or finished basement.
Heating portion only — subtract ~250 m³ for a gas water heater.
Your estimate
Design heating load
43k BTU/h
≈ 12.6 kW at -19 °C
Equivalent size
3.6 tons
of heating capacity needed at design temperature
Check from gas use
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add gas use above
Look for a cold-climate heat pump that can still deliver about 43k BTU/h at -19 °C, or one slightly smaller paired with backup heat. Nominal “ton” ratings describe cooling capacity at mild temperatures; heating output at −20 °C is often 60–90% of that, so ask for the manufacturer's capacity table.
This is a screening estimate only. A proper room-by-room load calculation (CSA F280) is required for rebates and good comfort. Read why sizing matters or ask contractors for a load calculation.
Assumptions and method
Design load = whole-home heat-loss coefficient × floor area × (21 °C − design temperature). Coefficients range from about 2.2 W/m²·K for pre-1960 homes to 0.95 for homes built after 2012, reduced 10% for each completed envelope upgrade.
When you enter gas use, the calculator also derives your home's heat-loss rate from actual consumption and regional heating degree days, and weights that estimate two-to-one over the age-based one.
Design temperatures are approximate values for each area under the Ontario Building Code.