District Energy St. Paul provides a superior alternative to on-site gas boilers by providing highly efficient hot water service. Hot water is generated at the central plant as well as satellite facilities, then circulated through underground pipes to buildings connected to the hot water system. Customers use the hot water to heat interior spaces, heat domestic hot water, melt snow on pavement, and for industrial processes. Once a customer building draws the energy it needs, the water is returned to the central plant for reheating then recirculated through the closed-loop piping system. The system circulates a volume of one million gallons of water per hour, with a supply temperature of 250 °F in the winter and 180 °F in the spring, summer, and fall. The system’s reliability has exceeded 99.99 % since service began.