This European Standard specifies test methods for the performance characterization of stores which are intended for use in small custom built systems as specified in FprEN 12977-1:2017. Stores tested according to this document are commonly used in solar combisystems. However, the thermal performance of all other thermal stores with water as a storage medium (e.g. for heat pump systems) can be also assessed according to the test methods specified in this document. This document applies to combistores with a nominal volume up to 3 000 l and without integrated burner. NOTE This document is extensively based on references to FprEN 12977 3:2017.