UNS Energy Corporation engages in the electric generation and energy delivery businesses. Its TEP segment generates, transmits, and distributes electricity to approximately 404,000 retail electric customers in southeastern Arizona. This segment also sells electricity to other utilities and power marketing entities. As of December 31, 2011, it owned or leased 2,262 MW of net generating capacity, as well as owned or participated in electric transmission and distribution system consisting of 512 circuit-miles of 500-kV lines; 1,088 circuit-miles of 345-kV lines; 405 circuit-miles of 138-kV lines; 479 circuit-miles of 46-kV lines; and 2,615 circuit-miles of lower voltage primary lines. TEP segment generates electricity from coal, gas, oil, and solar sources. The company’s UNS Gas segment distributes gas to approximately 148,000 retail customers in Mohave, Yavapai, Coconino, and Navajo counties in northern Arizona, as well as Santa Cruz County in southeastern Arizona. As of December 31, 2011, this segment’s transmission and distribution system consisted of approximately 31 miles of steel transmission mains, 4,220 miles of steel and plastic distribution piping, and 137,160 customer service lines. Its UNS Electric segment transmits and distributes electricity to approximately 91,000 retail customers in Mohave and Santa Cruz counties. As of December 31, 2011, this segment’s transmission and distribution system comprised approximately 56 circuit-miles of 115-kV transmission lines, 274 circuit-miles of 69-kV transmission lines, and 3,616 circuit-miles of underground and overhead distribution lines. It also owns the 65 MW Valencia plant and 90 MW Black Mountain generating station, as well as 39 substations having installed capacity of 1,494,000 kilovolt amperes. The company was formerly known as UniSource Energy Corporation and changed its name to UNS Energy Corporation in May 2012. UNS Energy Corporation was founded in 1902 and is headquartered in Tucson, Arizona.