Ground coupled heat pump (GCHP) systems are a good alternative to traditional systems for heating and cooling of buildings. A large number of ground coupled heat pump systems have been used in residential and commercial buildings throughout the world because of the attractive advantages of high efficiency and environmental friendliness, and a wide range of system configurations is available today. In this paper, a real application for an office building is presented. The schematic and main features of the GHCP system under study are outlined. The system was monitored during its operation, and experimental data are shown. Moreover, a dynamic simulation of the plant was performed by means of trnsys, and theoretical and experimental results are compared. The main purpose of the paper is to put in evidence the performance of such a system and to compare it with traditional heating/cooling systems. Energy and economic savings with GCHP operation were obtained. Eventually, a sensitivity analysis for the GCHP design parameters was performed.