In this study, a simple and cost effective solar assisted, heat pump system (SAHP) with flat plate collectors, a hot water storage tank and a water source heat pump has been proposed. The thermal performances of the whole system and its major components have been investigated experimentally during the 2000-2001 heating season in north China. From the experimentally obtained data, some important conclusions and suggestions have been acquired, which can be helpful in the primary design and improvement of a SAHP system for potential users.