The main focus of this paper is to analyze the energy and exergy efficiencies of a combined ground source heat pump (GSHP) system whose evaporator component works as a photovoltaic-thermal (PV/T) collector, and to determine the locations of the inefficiencies. This combined GSHP system consists of a heat pump cycle, a radiator thermal cycle, a ground heat exchanger cycle and a cooling tower cycle. The performance effects of the cooling tower have been examined, and optimal operation parameters have been selected to maximize the system efficiency. Exergy destruction rates, exergy efficiencies, exergy loss ratios of the system components and the whole system, as well as the energetic and exergetic coefficient of performance (COP) for the heat pump cycle have been evaluated for investigation of the potential improvement of the system components. From the results, exergy efficiency, COPsys and COPex of the system have been found as 74.72%, 2.895% and 039%, respectively. Additionally, parametric studies, including the thermodynamic performance of the system and its components, have been conducted by the change in some operating conditions, as variation of the ambient temperature changes from 0 degrees C to 30 degrees C, and the intensity of solar radiation that comes on the PV/T evaporator surface ranges from 400 W/m(2) to 900 W/m(2). (C) 2014 Elsevier Ltd. All rights reserved.