The refrigerant a heat pump utilizes for heat transfer is an important consideration when buying a new model. Almost all major brands of heat pumps on the market today have shifted from R22—also known as freon—to more environmentally sustainable refrigerants.

R22 refrigerant is a hydrochlorofluorocarbon that is known to deplete the ozone layer and can subject the earth to harmful ultraviolet rays from the sun. Freon refrigerant will be completely phased out of domestic use by the year 2020. Until that date, R22 is expected to become more and more expensive to obtain as manufacturers cease production and existing recycled stocks diminish. Other non-harmful refrigerants are available, but it is important to know that heat pumps that use R22 cannot be charged with the newer, safer refrigerants because the systems are incompatible.