This part of IEC 61853 describes the calculation of PV module energy rating values. IEC 61853-1 describes requirements for evaluating PV module performance in terms of power (watts) rating. IEC 61853-2 describes test procedures for determining module temperature from irradiance, ambient temperature and wind speed, a method for measuring angle of incidence effects, and spectral responsivity. IEC 61853-4 describes the standard reference climatic profiles (standard environmental data sets) that are used for calculating energy rating values. The purpose of this standard is to define a methodology to determine the PV module energy output (watt-hours), and the climatic specific energy rating (dimensionless) for a complete year at maximum power operation for the reference climatic profile(s) given in IEC 61853-4. It is applied to determine a specific module output in a standard reference climatic profile for the purposes of comparison of rated modules. The methodology does not take into account either progressive degradation or transient behaviour such as light induced changes and/or thermal annealing.