This study represents effect of four variables in performance of a heat-pump in two cities of Tehran and Rasht. A computer program has been developed, simulating a certain heat pump acting in different environments with different refrigerants in heating season. The analysis is based on a homogeneous model. Effect of different refrigerants, depth of the buried heat exchangers and moisture content of soil has been studied. The first and second law of thermodynamic has been used for evaluating energy and exergy performance of system and its components. The effect of moisture content of soil between two cities of Tehran and Rasht was compared. Results show that there is an optimum depth for horizontal heat exchanger. Also the analysis show that increasing refrigerant mass flow rate decreases energy efficiency where increases exergy efficiency.