The city of St. Paul pioneered its district energy system in 1983 in partnership with the State of Minnesota, US Department of Energy and area businesses. Designed to provide reliable, economical heat to the downtown area through a centralized hot water system, District Energy St. Paul now heats over 190 buildings plus 300 homes. It added a cold water-cooling system in 1993, which serves 100 buildings. More recent innovations make the operation a leader in renewables. A combined heat and power (CHP) system uses renewable fuel from locally sourced recycled wood, like downed trees and branches, to produce 65 MW of thermal energy and 25 MW of electricity that is sold to the local utility. District Energy St. Paul also installed a 1.2 MW solar hot water heater, the largest in the Midwest.