The heat pump is a heat multiplier. It takes warm air and makes it hot air. This is done by compressing the air and increasing its temperature. Heat pumps received more attention during the fuel embargo of 1974. Energy conservation became a more important concern for everyone at that time. If a device can be made to take heat from the air and heat a home or commercial building, it is very useful.
The heat pump can take the heat generated by a refrigeration unit and use it to heat a house or room. Most of them take the heat from outside the home and move it indoors (see Fig. 2-11). This unit can be used to air condition the house in the summer and heat it in the winter by taking the heat from the outside air and moving it inside.