Geothermal heat pumps or ground source heat pump (GSHP) are arrangements uniting a heat pump with a high enthalpy geothermal resources (ground heat exchanger in closed loop systems), or provided by ground water from a well in open loop systems. One of world’s largest uses of energy is the heating and cooling of buildings. Ground Source Heat Pumps (GSHP) provide a more energy efficient way to meet building energy needs than conventional alternatives. At a relatively shallow depth, the ground temperature is nearly constant year round providing a reliable heat source or sink for the operation of a heat pump. This study deals with reviewing heat pump studies and in the first part of this study, historical development of GSHPs was briefly given, and finally, studies conducted on GSHPs were reviewed.