District heating (less commonly called teleheating) is a system for distributing heat generated in a centralized location for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels but increasingly biomass, although heat-only boiler stations, geothermal heating and central solar heating are also used, as well as nuclear power. District heating plants can provide higher efficiencies and better pollution control than localized boilers. According to some research, District Heating with Combined Heat and Power - CHPDH is the cheapest method of cutting carbon, and has one of the lowest carbon footprints of all fossil generation plants.

More info: http://en.wikipedia.org/wiki/District_heating