This Technical Specification specifies test methods for the performance characterization of stores which are intended for use in small custom built systems as specified in CEN/TS 12977 1. Stores tested according to this document are commonly used in solar combisystems. However, also the thermal performance of all other thermal stores with water as storage medium (e.g. for heat pump systems) can be assessed according to the test methods specified in this document. This document applies to combisstores with a nominal volume up to 3 000 l and without integrated burner. NOTE This document is extensively based on references to EN 12977-3:2008.