This document specifies test methods for the performance characterization of hot water stores (hereinafter called stores) which are intended for use in small custom built systems as specified in EN 12977-1. 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 (for example, 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. This document is extensively based on references to EN 12977-3:2012. This document (EN 12977-4:2012) has been prepared by Technical Committee CEN/TC 312 "Thermal solar systems and components" (secretariat: ELOT, Greece). Working Committee NA 041-01-56 AA "Solaranlagen" ("Solar systems") at the Heating and Ventilation Technology Standards Committee (NHRS) at DIN, the German Institute for Standardization e. V. has been involved in the preparation of this European Standard.