The main function of a heat pump is to move heat from one area to another. Heat pumps are different from furnaces in that they do not use fuel to burn and create heat. Heat pumps generate and extract their own heat. In the winter, they take heat from the outside air and transfer it to the indoor air, which is then circulated through your home. In summer, the process is reversed and your heat pump removes heat from your indoor air and sends it outside. This keeps the inside cool.