Solar heating systems with seasonal energy storage have attracted an increasing attention over the past decades. However, studies of such systems using a phase change material (PCM) as seasonal storage medium have not been found in the open literature. In this paper a solar heat pump heating system with seasonal latent heat thermal storage (SHPH-SLHTS) is firstly described. This is followed by reporting the development of a simplified mathematical model for a SHPH-SLHTS system. Using the model developed, the operational performances of a SHPH-SLHTS system which provided space heating to a villa building have been investigated by simulation, and simulation results are reported in this paper. (C) 2008 Elsevier Ltd. All rights reserved.