"Heat pump" typically refers to a refrigeration cycle unit that uses a working fluid to transfer heat from a cold body to a hot body. An air conditioner uses th

"Heat pump" typically refers to a refrigeration cycle unit that uses a working fluid to transfer heat from a cold body to a hot body. An air conditioner uses this mechanism to heat the outside of the home (cooling the inside). Technically electricity is not required, although most of these units, in practice, use electricity, converted to mechanical energy, to power compressors. Heat pumps are much more efficient than e.g. electric baseboard heating because the energy consumed is used to move heat, rather than to generate heat. The efficiency difference drops in "very" cold climates (ambient temperatures well below freezing) and in those climates the heat pump usually is backed up by a direct heating method such as resistance electric heating, gas furnace, et cetera.