The purpose of this research is to determine the optimum orientation and size of a solar collector to be integrated with a basic-CCHP system. The basic-CCHP includes an internal combustion engine; absorption chiller and possible auxiliary boiler but the hybrid-CCHP is the basic-CCHP plus a solar collector to provide a portion of the thermal energy demand of the consumer. Maximum rectangle method is used to size the prime mover. Size of other components depends on the engine size and building demands. The building which the hybrid-CCHP is supposed to be designed for is a residential building. The optimum conditions for the solar collector are determined in five different climates, and the privileges of using a hybrid-CCHP system instead of the basic-CCHP system are discussed. Furthermore, the impact of full load and partial load operation of engine on the fuel energy saving ratio (FESR) of the basic-CCHP and hybrid-CCHP is discussed. The results showed that for the hybrid-CCHP more FESR is achieved in partial load operation of engine, on the contrary, for the basic-CCHP the FESR is higher when the engine operates in full load. (C) 2015 Elsevier B.V. All rights reserved.