The NRE 3GS21C is a low-emissions diesel genset locomotive built by National Railway Equipment (NRE). It is powered by three Cummins QSK19C I6 engines with each one developing 700 horsepower (522 kW) and creating a total power output of 2,100 horsepower (1,570 kW). Instead of a single prime mover, the NRE genset locomotive has three engines that each can be turned off or on as power is needed reducing overall diesel emissions and improving fuel efficiency. At least 27 3GS21C genset locomotives have been produced to date at NRE's Mount Vernon shops in Southern Illinois.