Heat pumps require a high volume of air in order to maintain a reasonable compression ratio at the compressor. There are dual-compressor heat pump models that operate more efficiently at lower temperatures. At temperatures where conventional heat pumps switch to the more costly resistance heat, the dual-compressor units turn on their second compressors, which are designed to extract further BTU's from the outside air. While heat pumps have an expected economic life span of 5 to 8 years, with annual servicing and operator care, extra life can be added. Be aware of the importance of cleaning or replacing air filters.
Clean filters are more important for heat pump systems than for conventional systems.
Understand that the 85 to 90F supply temperatures are sufficiently higher than the 70F room temperature to maintain the room temperature at the desired level. Realize that the ice formation on the outside coil is a normal part of the heat pump operation, as is the periodic defrost cycle. Maintain the heat pump above the prevailing snow line with clearance on the sides and bottom. Expect the unit to run continuously at low outdoor temperatures. Understand the purpose of the emergency heat switch.