Wastewater treatment is very energy intensive and accounts for a high share of total energy consumption of municipal consumers. On the other hand, wastewater treatment plants produce residues with a high energy content, which can be used in further processes. Using the right combination of waste water treatment plants, sludge gasifiers and Power-to-Gas plants it is possible to create synergies leading to energy efficient systems. The aim of this thesis is the analysis of mass-, energy- and exergy balances of three different combinations of the integration of Power-to-Gas plants into wastewater treatment plants. Therefore, models based on thermodynamics were implemented in Matlab/Simulink. The input values for the models derive from an Excel tool for quasi-dynamic mass- and energy balances for waste water treatment plants developed at the chair of Energy Network Technology. For a deeper understanding of the system characteristics, the analysis was executed for a variety of configurations of the waste water treatment plants in combination with Power-to-Gas technology. Subsequently, diagrams for the estimation of the amount of produced substances and energy were established based on the analysis. The thesis is summed up by creating flow diagrams in STAN2 out the results of the model.