Phase change materials (PCM) as heat storage theoretically offer an advantage compared to water stores on the one hand, when the cycling temperature is close around the phase change temperature and the phase change can be used quite often. Another application is the use of the subcooling effect of certain PCM for seasonal storage. The scope, in terms of general system aspects for IEA SHC Task 32, was solar heating and cooling systems for residential buildings, principally detached houses for one up to a few families. Additionally other promising heating or cooling systems were taken into consideration. Five projects dealing with PCM modules in solar combistores, seasonal storage with subcooled PCM and PCM in residential heating systems as space heating stores were investigated in the laboratory and by simulation studies. However, the investigations reported here showed only little advantages for macro-encapsulated PCM modules in combistores, PCM-stores with immersed heat exchangers and for PCM slurries for heat stores in solar combisystems and residential heating systems. The seasonal storage with subcooled PCM could be in principle a good solution. However the technical expenditure for this system is large.