In order to improve the performance of the solar-assisted heat pump system with energy storage for domestic heating in the Black Sea region of Turkey, an experimental set-up was constructed. In this study, the solar-assisted series heat pump system with storage and parallel heat pump system with storage are experimentally investigated and compared. This experimental apparatus consists of 30 m2 of flat-plate solar collectors, a laboratory with 75 m2 floor area for heating purposes, a latent heat thermal energy storage tank that is filled by 1500 kg of encapsulated phase-change material (PCM), a heat pump with double evaporators (air- and water-sourced) and one condenser, a water circulating pump and other measuring equipment. The experimental results are obtained in December, January, February, March, April and May in the heating season of 1991 for the two heat pump systems used. The experimentally obtained results are used to calculate the collector efficiency, heat pump coefficient of performance (COP), system COP, storage efficiency and total energy consumption of the system during the heating season. The mean values of the collector efficiency, heat pump COP, system COP and storage efficiency were around to be 70, 4.2, 4.0, and 60%, respectively.