This European Standard is part of a series of standards on the method for calculation of system energy requirements and system efficiencies of space heating systems and domestic hot water systems. This standard (prEN 15316-4-1) specifies: ¾ð required inputs; ¾ð a calculation method; ¾ð resulting outputs; ¾ð a method to take into account the energy performance of heat generation devices based on fuel combustion. for space heating generation by combustion sub-systems (boilers, biomass), including control. This standard also specifies methods for the calculation of: ¾ð thermal losses from the domestic hot water generation system; ¾ð recoverable thermal losses for space heating from the domestic hot water generation system; ¾ð auxiliary energy of the domestic hot water generation systems. This standard specifies the energy performance calculation of water based heat generation sub-systems including control based on combustion of fuels ("boilers"), operating with conventional fossil fuels as well as renewable fuels. This standard does not cover sizing or inspection of boilers. This standard is also applicable to heat generators for heating or for combined service as domestic hot water, ventilation, cooling and heating. Generators for domestic hot water only are taken into account into part M8-8. This European Standard is the general standard on generation by combustion sub-systems (boilers, biomass) and is also intended for generation for domestic hot water production and/or space heating. These values are input data for calculation of the overall energy use according to prEN 15603 and prEN 15316-1.