What does "reversibility" refer to in heat pumps?

Reversibility in heat pumps refers specifically to the capability to switch between heating and cooling modes. This characteristic is fundamental to the operation of heat pumps, as they can extract heat from outside air, ground, or water and transfer it indoors for heating during colder months. Conversely, in warmer months, they can reverse the process, removing heat from the indoor air and expelling it outside to provide cooling.

This dual functionality is what distinguishes heat pumps from traditional heating or cooling systems, making them versatile and energy-efficient solutions for maintaining comfortable indoor temperatures throughout the year.