This standard describes the calculation of the energy effort for heat and cold generation. Input energy may originate in the environment or fuels (solid, liquid, gaseous) or may be electrical. The standard allows to evaluate the energy efficiency of generators to be installed or existing ones already in use. The numerical reference values given in the standard, however, refer to current aggregates only. This standard and the other parts of the series of standards VDI 2067 represent an overall system, which means that the standard is to be applied in conjunction with these parts. Fundamentals and the calculation process are illustrated for an exemplary vesse