In this study, a prototype of an aqua-ammonia absorption heat pump system (AHP) using solar energy was investigated. The performance tests of the system were performed for the climate condition of Ankara in Turkey. The system has been designed operating with a parabolic slote type collector to obtain the required temperatures. In the experiments, high temperature water obtained from the collector was used as heat source needed for the generator. The system design configuration was analysed by using the experimental data. The effect of irreversibilities in thermal process on the system performance in AHP were determined. Thermodynamic analysis shows that both losses and irreversibility have an impact on absorption system performance. The study indicates which components in the system need to be improved thermally. This study will contribute the development of the system for the future use of solar-powered food preservation and commercial air conditioning. (C) 2002 Elsevier Science Ltd. All rights reserved.