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 prCEN/TS 12977-1. Stores tested according to this document are commonly used in solar hot water systems. However, also the thermal performance of all other thermal stores with water as storage medium can be assessed according to the test methods specified in this document. The document applies to stores with a nominal volume between 50 l and 3000 l. This document does not apply to combistores. Performance test methods for solar combistores are specified in prCEN/TS 12977-4.