This European Standard is part of a set of standards covering methods for calculation of system energy requirements and system efficiencies of heating systems in buildings. In particular this European Standard is one of a number of standards dealing with domestic hot water systems. The scope of this specific part is to standardise the methods for determining the energy needs for domestic hot water. This European Standard covers the domestic hot water needs in buildings. The calculation of the energy needs for domestic hot water applies to a dwelling, a building or a zone of a building. In order to be coherent with calculation methods for space heating systems, emission losses representing taps and control should be taken into account.