Heat Pump Sizing Calculator

A whole-house CSA F280:12 load calculation — verbatim conductive tables, the AIM-2 air-leakage model, and the BASESIMP below-grade model. Get your design heating and cooling load and a recommended heat pump size.

Frequently Asked Questions

What size heat pump do I need?

Heat pump size is set by your home’s design heating load — the heat lost on the coldest design day — not by a flat BTU-per-square-foot rule. This calculator runs a whole-house CSA F280:12 load calculation: verbatim F280 conductive tables, the AIM-2 air-leakage model, and the BASESIMP below-grade model. Enter your home details for a design heating and cooling load in watts and BTU/h, plus a recommended heat pump capacity. A registered Energy Advisor or HOT2000 report is still required for rebate or code submissions.

Is this a real CSA F280 calculation?

It uses the CSA F280:12 methodology: the conductive heat-loss tables are verbatim from the standard, air leakage uses the AIM-2 model (Walker-Wilson / HOT2000) that F280 §5.2.3.1 references, and below-grade uses the BASESIMP model (NRCan) that F280 §5.2.2 specifies. Validated against F280’s own published §8.3.9 reference home to within about 2%. It is an estimate, not a certified F280 report — a registered Energy Advisor or HOT2000 run is required for rebate or permit submissions.

What happens if my heat pump is the wrong size?

An undersized heat pump runs continuously, can’t hold setpoint on the coldest days, and wears out early. An oversized unit short-cycles — starting and stopping too often — which hurts efficiency, humidity control, and compressor life. Right-sizing to the design load is what keeps a heat pump comfortable and efficient.