Although the main function of a wastewater treatment plant (WWTP) is to remove various constituents from wastewater it can also serve as a source of energy and other materials. The generated resources can be used either on-site at the WWTP or elsewhere at an adjacent infrastructure. In the course of a current national research project, the possibilities and potentials regarding the integration of WWTPs into local energy supply concepts are being investigated in Austria. Preliminary results show that in particular the amount of thermal energy available exceeds by far the on-site demands of WWTPs. Even on-site electrical energy demands could be self-addressed under certain conditions. This paper describes the estimation of total energy consumption and generation and the related degree of energetic self-sufficiency at certain Austrian WWTPs. Preliminary results regarding the development of a tool for evaluating and optimising on-site and externally supplied use of energy are presented. Finally, the possibilities of energy supply for neighbouring spatial structures are discussed briefly and conclusions drawn about the potential to develop WWTPs as regional energy cells.