It is necessary for optimum design of GSHP systems to estimate accurately thermal properties of the designed ground and predict the heat extraction rate from the ground. Generally, experimental analysis has been used for the feasibility of system introduction such as thermal response test, pumping test or cone penetrating test, but it causes to increase estimation cost before the introduction, equivalent to tens of thousands of dollars in Japan. On the other hand, the heat exchange rate and the effect of the system on underground environment can be predicted by using numerical simulation. In this research, in order to estimate the effect of the ground thermal properties on system performance, numerical simulation has been conducted through the sensitivity analysis with the developed simulation tool. Furthermore, the method to develop an energy potential for GSHP system has been suggested and its application for Tokyo 23 ward area has been conducted with GIS data. (C) 2010 Elsevier B.V. All rights reserved.