Heat Pump Sizing

Heat pump sizing is about choosing the right unit to heat and cool your home effectively. With traditional a/c ands heating systems there isn’t much downside to simply oversizing equipment. Customers aren’t likely to complain about too much heating and cooling capacity.

A heat pump that’s undersized or oversized will cause problems though — so sizing is an important process.

There's an Art to Heat Pump Sizing

Correctly sizing a heat pump is a bit tricky for several reasons:

A single heat pump handles both winter heating and summer cooling. So the unit has to be balanced to meet two different needs (in most of Canada heating is more demanding).
Heat pump efficiency and capacity decrease at lower temperatures — complicating the calculations.

Problems Caused by Wrong-Sized Heat Pumps

Undersized Heat Pumps

Won’t be able to keep up with heating demand so it leaves your home cold.
Won’t be able to handle the optimal amount of heating in a dual-fuel (aka hybrid) system.

Oversized Heat Pumps

Will run in brief bursts rather than the steady low speed that’s ideal…
- Reducing dehumidification capability when cooling.
- Leading to hot and cold spots in your home when heating.
Bigger units can cost substantially more — so you’re overpaying if you’re oversized.
Larger units often need upgrades to ductwork to move the additional air they push — so you end up paying for duct work or throttling the ability of your heat pump.

What's the Goal of Heat Pump Sizing?

An expert contractor will put real work into the sizing question. They should do heat and cooling load calculations or use the calculations from an Energuide home energy assessment.

Knowing heating and cooling loads provides a solid foundation. From that your contractor should carefully select equipment that will meet your needs.

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