This paper presented a novel hybrid solar GSHPS (HSGSHPS) composed of a GSHPS and a solar assisted GSHPS (SAGSHPS) used in an office building for heating and cooling. The key issues of designing the HSGSHPS were introduced and a simulation model was developed in TRNSYS to predict the multi-year performance of this system. The simulated results showed that the proposed HSGSHPS was reasonably designed to resolve the ground temperature imbalance problem on an annual basis. The suitable control strategy for the solar collection and storage was found according to the coefficient of performance (COP) of SAGSHPS. The first-operation time has impact on the operation of SAGSHP and GSHPS. Injection of thermal energy into the borehole heat exchanger (BHE) or borehole thermal energy storage (BTES) before the heat extraction from BHE/BTES was favourable to the overall COP of system. It is very important to SAGSHPS to store sufficient solar thermal energy in the BTES because of its small spacing between boreholes. 32% of the electrical energy consumption in the HSGSHPS could be saved if the load circulation pump was turned off when no fan-coil was running, rather than always keeping it running at all times. (C) 2011 Elsevier B.V. All rights reserved.