Heat pumps in cold climates: sizing, balance point and backup heat

Heat pumps are one of the most common renovation upgrades in Canada now, and one of the easiest to get wrong on paper. The mistakes are usually in sizing and in how backup heat is set up, not in the equipment brand.

The balance point

NRCan describes the thermal balance point as the outdoor temperature at which the heat pump's heating capacity equals the house's heat loss. Below it, backup heat makes up the difference. A separate economic balance point is where switching to backup becomes cheaper, depending on electricity and fuel prices, the heat pump's efficiency and the backup system's efficiency.

Cold-climate units and backup

NRCan says modern cold-climate heat pumps can operate reliably down to about -30 C. In the coldest regions, auxiliary heat is still needed to avoid risks such as frozen pipes. Plan the backup as part of the design, not as an afterthought.

Size from a heat loss calculation

NRCan's sizing guidance refers to the CSA F280 heat loss standard, under which the total heating capacity of all systems must be at least the building's calculated heat loss. Ask the contractor for the heat loss calculation and for how much of it the heat pump covers at your design temperature. NRCan publishes a free sizing and selection guide for energy advisors and designers.

Hybrid or all-electric

A hybrid system keeps a furnace or boiler as backup and switches at the thermal or economic balance point. An all-electric system uses electric resistance backup in the ducts or baseboards; NRCan recommends setting the supplementary heat 2 to 3 C below the heat pump set-point so it does not run unnecessarily.

What to ask in a quote

Which heat loss calculation was used, the heat pump's capacity at your design temperature, the balance point, the type and control of backup heat, and whether the ducts can carry the airflow. Electrical capacity and permits are part of the job too.

Prevention Checklist

• Ask for a room-by-room or whole-house heat loss calculation.
• Ask for the heat pump's capacity at your local design temperature.
• Ask where the balance point is and how backup is controlled.
• Set electric backup 2-3 C below the heat pump set-point.
• Check electrical capacity and permits before installation.

References

1. Natural Resources Canada. Air-Source Heat Pump Sizing and Selection Guide, Web page, Balance points; sizing; backup. Accessed 2026-11-01.
2. Natural Resources Canada. Best practices in heat pumps, Web page, Switchover; cold-climate operation. Accessed 2026-11-01.
3. Natural Resources Canada. Heating and cooling with a heat pump, Web page, Overview. Accessed 2026-11-01.

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