Energy recovery in wastewater treatment plant is one of the ways to lowering operation costs. For energy conservation in wastewater treatment plants, it is helpful to outline briefly the main processes which consume most of the energy required in conventional wastewater treatment facilities. The research is conducted in Tabriz wastewater treatment plant, at the north west of Iran which has a design capacity of 1.5 m3 /s wastewater. The main focus of the work is on methane production potential of domestic wastewater. During this study which lasted six months, energy consumer units of plant were reviewed. Wastewater flow rate (Q), BOD5 and bCOD of wastewater in three points— plant influent, primary settling effluent and plant effluent—were tested. The potential of methane production was also estimated and converted to electrical energy. The results showed that by optimization of methane production and energy consumption in different units of plant, it is possible to provide 97% of plant electrical energy and all of another form of energy as heat.