Heat pumps can be explained by the Clausius and Kelvin Statements. This being “Heat can not be transferred from cold to hot by itself” and “Heat can not be converted 100 % to work” respectively. Heat pumps work by adding energy to a system to move heat from areas of colder concentrations to warmer areas as seen in the graphic below .
The efficiency of a heat pump can be calculated with the equation
Heat pumps always have an efficiency greater than 1.