From July 2007 to August 2010, the first German project about energy efficiency in water supply was carried out. The project results are summarised in a guidance report entitled ‘DVGW-Information Wasser Nr. 77’. The DVGW Research Centre worked on assessing the energy saving potentials and a reduction in energy demand for German water supply systems. It is assumed that the energy-saving potential for German water utilities is in the region of 20%. Two main sections were identified as relevant for an investigation of energy efficiency in a water utility. First and foremost, a comprehensive and structured energy balance must be formulated. Based on this information, the energy saving potentials can then be assessed. In the above-mentioned guidance report additional energy saving potentials for all sections of the water supply industry were summarised. An energy balance for water supply must be related to different sectors and levels to guarantee a detailed energy efficiency evaluation. This in turn allows for a structured assessment of the energy saving potentials. In the majority of cases, specific investigations with detailed data capture are necessary. Based on these, an evaluation of applicable measures needs to be undertaken before the measures can be implemented and their success documented. The guidance report ‘DVGW-Information Wasser Nr. 77’ is a manual for these investigations and also includes tools for an energy efficiency analysis in water utilities.