entered commercial service and power began to be generated at Byron. The operating licenses for the two reactors are set to expire two years apart: Initially, Unit One's license expired on October 31, 2024, and Unit Two's on November 6, 2026. On May 29, 2013 Exelon Generation Co. applied to renew the licences and on November 19, 2015, based on a final safety evaluation report (July 6, 2015) and a supplemental environmental impact statement (July 15, 2015), the Nuclear Regulatory Commission renewed both operating licenses for an additional 20 years. The renewed licenses authorize Unit One to operate through October 31, 2044, and Unit Two through Nov. 6, 2046. In August 2020, Exelon decided to close plant in September 2021 for economic reasons, despite the plant having licenses to operate for another 20 years. Exelon stated it would continue discussions with policymakers to try to obtain support to prevent the closure. In August 2021, Exelon stated a proposed $15/MWh federal production tax credit (PTC) would not be legislated in time to avoid closing Byron and Dresden. However, by September 13, 2021, the Illinois Senate approved a bill containing nearly $700 million in subsidies for the state's nuclear plants, including Byron, causing Exelon to reverse the shutdown order. Facilities and output The two Westinghouse four-loop pressurized-water reactors each have an electrical output of over 1,000 MWe. Byron has 2 units capable of generating 2347 net megawatts (MW) of electricity. In 2009 the reactors operated at 96.4% capacity and produced 19.7 million MWh of electricity; enough power for 2 million average American households. The two cooling towers at Byron rise 495 feet (151 m) over the site. The plant utilizes non-contact cooling water from the Rock River, situated 2 miles (3.2 km) to the west. The water used in the process of generating electricity is cooled in the station's two cooling towers and recirculated via the plant's blowdown line back into the Rock River. Other water, from Byron's Radioactive Waste Treatment system, is transferred to the Refueling Water Storage Tank (RWST), where it is analyzed and sampled for contamination. Once it passes through analysis, the water is discharged down the blowdown line into the river. According to former plant owner Exelon, the Byron station is operated by about 850 Exelon employees and another 50 permanent contractors. Most of Byron's employees reside in Ogle and Winnebago Counties in northern Illinois. The plant paid