Home energy planning · Updated
Cold Weather Heat Pump: Capacity, COP & Backup Heat
A heat pump can be designed for cold weather, but one temperature claim cannot describe its capacity, comfort and running cost. Compare the actual model at your local design conditions.
Capacity and efficiency answer different questions
Capacity is the heat the equipment can deliver at a stated temperature. COP compares delivered heat with electricity consumed under stated test conditions. A system can operate at a low temperature without having enough capacity to carry the full building load there.
What to ask for in a cold-climate quote
- Heating and cooling loads calculated for the home and local design conditions.
- The exact matched indoor/outdoor equipment and low-temperature output tables.
- Expected supplemental heat requirements and the proposed controls.
- Defrost drainage, outdoor mounting and clearance provisions.
- Electrical work, installation commissioning and maintenance scope.
Capacity balance point vs economic break-even
The capacity balance point is where available heat-pump output meets building demand. The economic break-even point is where electricity and alternative-fuel operating costs match. They are different decisions. Neither should be set using a universal outdoor-temperature rule.
Compare gas with a heat pump using your rates
For an illustrative US gas comparison, break-even COP = electricity price per kWh × 29.307 × furnace AFUE ÷ gas price per therm. At $0.18/kWh, 95% AFUE and $1.50/therm, break-even COP is about 3.34. Above this value the modeled heat-pump energy cost is lower; below it gas is lower. This excludes fixed utility charges, maintenance and capital cost.
Backup heat changes the seasonal result
Resistance heat and fuel backup need to be included when comparing bills. Ask how often backup is expected to run and how the thermostat prevents unnecessary operation. A single point COP should not be used as the annual seasonal average.
Plan the outdoor installation
Ask the contractor how snow, service access and defrost water are handled at the proposed location. Have the electrical service and controls checked as part of the installation scope. The right design depends on the equipment and site; a planning calculator cannot commission the system.