The capacity and efficiency of conventional heat pumps drops in colder temperatures. Some conventional units shut down at outdoor temperatures around -8°C and below9 to protect themselves from damage, while others are rated to operate down to -12°C. However, heat pump technology has evolved to allow operation at outdoor temperatures as low as -25⁰C, with some manufacturers claiming that their units can operate in even colder temperatures. These heat pumps are known as cold climate heat pumps (ccASHPs). Cold climate variants of ductless, central, and mini-ducted ASHPs are available.
Cold climate ASHPs are generally more efficient at colder temperatures. They also typically offer higher supply air temperatures, which can improve occupant comfort and sometimes eliminate the need for duct improvements. Basic ccASHPs incorporate a larger compressor and a larger outdoor unit, which allows them to operate down to about -15°C. More advanced (and expensive) ccASHPs can operate at colder temperatures.
These units incorporate features such as variable speed fans, higher efficiency compressors, variable speed ECM compressor motors, and communications between the outdoor and indoor units. Some of these features are incorporated into some conventional ASHPs as well.
Northeast Energy Efficiency Partnerships (NEEP) maintains performance requirements for ccASHPs and a list of qualified units that meets these specifications9.