Since 1985, Ellerbe Becket has aided NRG in developing their downtown Minneapolis district energy system. When a building is connected to the system, the piping must be reviewed and possibly rerouted. Plants are remodeled to deliver additional capacity efficiently, and occasionally a new plant must be built. The system currently includes 6 cooling and 5 heating plants. Some facilities are cooling only, heating only and the others are both heating and cooling. They supply heating and cooling to virtually all high-rise buildings downtown and also the city’s stadium, arena and convention center.