The T.B. Simon Power Plant is the third power plant on MSU's campus. Its most recent predecessor is the Shaw Lane Power Plant (still standing east of Spartan Stadium and operating as an electrical substation). The T.B. Simon Plant, located on Service Road between the train tracks, was developed in segments, ultimately taking over the title as MSU's chief power provider in the mid-1970s. Two boiler units were built in 1966 and a third followed in 1974 and another in 1993. In 2006, the plant added Unit 5, a steam turbine/generator, and Unit 6, a natural gas combustion turbine and companion heat-recovery steam generator. These additions significantly increased the plant's capacity and efficiency. It can now produce 1.3 million pounds of steam per hour and 100 megawatts, making it one of the top 500 generating plants in America.