Air-to-air heat pumps work by transferring heat between outdoor air and indoor air — using the same basic technology as a refrigerator or air conditioner, but reversible.
A heat pump doesn’t create heat — it moves heat from one place to another using a refrigerant cycle.
In heating mode, it extracts heat from the outside air and moves it indoors.
In cooling mode, it does the opposite — removing heat from inside and releasing it outdoors.
Even when it’s cold outside, there’s still some heat energy in the air.
Modern air-source heat pumps can extract heat efficiently from outdoor air down to –15 °C (5 °F) or even lower with advanced designs.