To apply a ground source heat pump system, it is important to evaluate the system performance by a simulation that considers the thermal storage capacity of the ground. In the present study, employing analytical and numerical methods in combination, we developed a ground heat exchanger simulation model having the advantages of both methods. Thus, the newly developed model permits reducing the computing load in system simulation. By comparing the simulation results with the results of FEM analysis and measurement, we confirmed that the developed model had sufficient accuracy. In addition, we presented a method of evaluating the heat performance of a ground heat exchanger on a time scale and showed the evaluated heat performances of several different heat exchangers.