Quick answer
Natural Resources Canada recommends sizing a heat pump to cover the majority of your home's annual heating energy, not the single coldest day, with supplementary heat covering occasional peaks. Sizing starts with a heat-loss calculation for your home.1
Why not size for the coldest day?
The coldest nights happen only a few times a year. Sizing an air-source heat pump to meet that peak on its own usually means a larger, more expensive system that runs below its best capacity most of the time. NRCan's guidance is to size for most of the annual heating need and let a supplementary system handle occasional peaks.1
What goes into sizing
- Heat loss: insulation levels, windows, air leakage and the size of the home.
- Climate: your area's design temperature.
- Backup heat: whether you'll keep a furnace or use electric elements.
- Ductwork: whether existing ducts can carry the airflow.
Efficiency first changes the answer
Sealing air leaks and adding attic insulation reduce heat loss, which can mean a smaller heat pump. That's why insulation comes in the first phase of our plans, before equipment is sized.
Size affects the rebate
Ontario's heat pump rebate is calculated per ton of capacity up to a maximum, for example $1,250 per ton up to $7,500 for cold-climate air-source heat pumps in homes not heated with gas.2
Common follow-up questions
What is a ton of heat pump capacity?
A ton is a unit of heating or cooling capacity equal to 12,000 BTU per hour.
Can a heat pump be too big?
An oversized system costs more to buy and can cycle on and off more often. Proper sizing starts with a heat-loss calculation.
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Answers are general information as reported by the sources listed on the date shown, not personal financial or technical advice. Programs, prices and rules change. Canadian Energy Standard is an independent company, not affiliated with any government, utility or program named here.