Wastewater treatment is one of the largest energy consumers in a municipality. The results of energy analysis conducted show great potential for increasing energy efficiency of wastewater systems. In view of the complex process sequences in wastewater disposal, a systematic approach and extensive expertise is necessary with regard to the energy optimisation of wastewater systems. There is no standard nationwide methodology to evaluate the energy efficiency of wastewater systems to date. The present Standard introduces the energy check and energy analysis as instruments for energy optimisation of wastewater systems and formulates requirements for their execution. The scope of application of this Standard covers wastewater treatment plants and wastewater collecting. Analogue to pumping stations in wastewater treatment plants, pumping stations in the field of wastewater collecting are open to an energetic assessment by means of the presented approaches. At present no adequate systematically collected operational experience has been gained in the field of rainwater and combined wastewater treatment plants (e.g. retention soil filters etc.). The same applies for compressed air flow, pneumatic conveyance, vacuum drainage and pressure main networks.