The aim of the work is to examine the influence of different refrigerants and different working conditions on specific energetic values in the heating mode of a heat pump. The possibility of applying spreadsheet calculator to a real thermodynamic process using the REFPROP base of thermodynamic parameters for real fluids is examined. Using experimental data taken from a geothermal heat pump there is also included the heat transfer from the ground to the secondary fluid in the borehole heat exchanger, and the processes in other heat exchangers, such as evaporator and condenser. Thermodynamic process is shown in the respective comparative thermodynamic diagrams in order to clearly see the different properties of refrigerants and their impact on the energy characteristics of the heat pump. Also, the energy characteristics of different refrigerants are analysed for the same temperature conditions. The following refrigerants are included: propane, isobutane, rejected R-12 and its environmentally friendly and widely accepted replacement R-134a, and for comparison ammonia as the most commonly used refrigerant. In the heating mode there is analysed how the changes in evaporation temperature of refrigerant at constant condensation temperature (pressure) influence the unit workloads, cooling capacity, heat of condensation, temperature after compression, and the heating coefficient of a heat pump. Furthermore, the influence of different temperature regime on characteristic energetic values is examined.