Municipal wastewater treatment is something most people do not give much thought to. You flush and what happens next is out of sight, out of mind. Functional wastewater treatment and collection systems are one of the most important factors in development and protecting the environment. Quality wastewater treatment is one of the things that separates developed countries from developed countries. Municipal wastewater treatment also consumes a significant amount of energy and is often the largest consumer of energy within municipal government. Fortunately, most municipal wastewater treatment plants (POTWs) can significantly reduce their energy consumption by implementing efficiency measures and generating electricity from anaerobic digester biogas, a renewable fuel. Like most other infrastructure in the US, municipal wastewater treatment and collection systems are in a state of disrepair and require large investments. From an energy standpoint, this presents an opportunity to install more efficient equipment and processes that produce biogas, a renewable fuel. Based on my research, if all POTWs implemented efficient pumping and optimized aeration, POTWs could reduce their energy needs 547 – 1,054 million kWh per year, or 3 – 6% annually. If all POTWs utilizing anaerobic digestion generated electricity with the produced biogas, POTWs could reduce their energy needs 2,320 – 3,480 million kWh per year, or 13 – 19% annually. Reducing POTWs energy consumption reduces carbon dioxide (CO2) emissions from electricity generation. By fully implementing efficiency measures and generating electricity from all existing biogas, POTWs can reduce CO2 emissions by 1.99 – 2.68 million metric tons annually. POTWs are a hidden source of energy savings and renewable fuel. Any local government or utility wanting to reduce energy use and greenhouse gas emissions should look to their local POTWs and at the least every POTWs in the US should conduct a periodic energy audit to check for potential energy saving and the possibility of energy production.