Aren't heat pumps also refrigerant-based? As I understand it, a heat pump is an AC unit that can be driven backward. In heat mode, they are air conditioning th

Aren't heat pumps also refrigerant-based? As I understand it, a heat pump is an AC unit that can be driven backward. In heat mode, they are air conditioning the already-cold outside, which works as long as the compressor can chill the refrigerant lower than the ambient outside air. They even use the same refrigerant, usually R-410A and R-454B.