The goal of this Diploma Thesis is to deliver an integrated view on EPFL as an energy system. It shall support future decision making about further steps towards increased sustainability and efficiency at EPFL, regarding the energy system. The results of the Thesis allow the comparison of different measures with respect to costs and energy savings. Beginning with the current status, the largest energy consumers are identified, and the energy consumptions are categorized in order to show the flash points of possible actions. Subsequently, an efficiency analysis is conducted over three different stages. First, the main services related with significant energy consumption are examined for possible efficiency measures, and significant saving potentials for the different services are identified. The greatest savings pertains to the ventilation system. In the second stage, the options for energetic integration are investigated to reveal synergies between thermal streams. The conversion system is the focus of the last stage. Here, the CO2- intensity and the effects of the heat distribution network extension on the existing heating system are analyzed.