For example, heat pumps and air conditioners are closely related because they use similar components and processes, but they aren't quite the same thing. Heat pumps and air conditioners both use refrigerant and a compressor to transfer heat rather than generate it. When a heat pump is operating in cooling mode, it functions like a conventional air conditioner by pulling heat from inside the space and then releasing it outside the home. However, despite this extremely common myth, a heat pump can also effectively warm a home when in heating mode. This is because of a component called a reversing valve, which allows a heat pump to take heat from the outside air and move it indoors.