Sewage sludge is outcome of the wastewater treatment process. It contains hazardous biological and chemical compounds that need to be stabilized. Anaerobic digestion is among the stabilization methods of sewage sludge. Digestion process destroys organic fraction of sewage sludge and produces biogas (%65 Methane, %34 CO2 and etc.). Biogas is burned in internal combustion engines to produce electricity. Digested residue can be used fertilizer. In this study, the total electricity production that can be obtained by anaerobic digestion of all wastewater treatment plants throughout the country is examined. Main objective of this study is preliminary evaluation of energy potential of biogas from sewage sludge anaerobic digestion. Since Wastewater Treatment Plants are distributed in the various regions of a city, above mentioned biogas plants should be considered as distributed generation equipment. Use of small scale energy production plants near the consumers is called distributed generation. Energy transmission losses and related infrastructure cost can be reduced or delayed by means of distributed generation. Within a smart grid approach, mentioned plants can support electricity grid. They can also serve as local emergency power plants. As a nationwide scenario WWTP are evaluated. Biogas energy capacity potential of 234 plants is calculated. Capacities less than 100 kWe are assumed to be non-feasible due to scale economy. It is evident that 91 plants can be installed with an average capacity of 660 kWe.