While heat pumps are most efficient in moderate climates, advancements in technology have made them a viable option even in colder regions. Modern heat pumps can operate in temperatures as low as -13°F (-25°C), thanks to advancements in refrigerant technology and system design. However, in extremely cold climates, a supplemental heat source, such as an electric resistance heater or a gas furnace, may be necessary to maintain comfortable indoor temperatures. Talk to an HVAC professional to determine what's best for your area.