Arizona Public Service (APS) is the largest electric utility in Arizona, United States. Since 1985, it has been the principal subsidiary of publicly traded S&P 500 member Pinnacle West Capital Corporation, known as AZP Group until 1987. Pinnacle West Capital made a profit of $500 million in 2017. With 4,000 MW of generating capacity, APS serves more than one million customers in 11 counties throughout most of the state, but mainly concentrated in northern and central Arizona. APS is one of the two major suppliers of electricity to the Phoenix metropolitan area (the other being Salt River Project (SRP)). APS is regulated by the Arizona Corporation Commission (ACC), the state agency that, by mandate of Article 15, Section 2 of the state's constitution, regulates energy utilities in Arizona, with the notable exception of SRP, the rural electrical districts, and the City of Mesa electric utility serving Downtown Mesa and the immediate vicinity (with the rest of the city being served by SRP). The holding company, Pinnacle West Capital, through its APS utility sells wholesale and retail power to the wider western United States and also provides energy-related services. Through another major subsidiary, Pinnacle West also developed and managed real estate in Arizona. Pinnacle West left the real estate business in 2010. The utility company also operates three nuclear reactors. Its Palo Verde Nuclear Generating Station in Arizona, the largest nuclear plant in the U.S., came under scrutiny by the Nuclear Regulatory Commission in 2005 when operational problems began to cause prolonged outages. History In 1884, the Phoenix Light and Fuel Company was formed to provide electricity and heat to the people of the three-year-old town of Phoenix. It changed its name to Pacific Gas and Electric Company in 1906 and to Central Arizona Light and Power in 1920. Also in 1920, it paid a dividend, and continued the annual dividend without interruption for the next 69 years. The company became a subsidiary of the giant conglomerate American Power and Light in 1925, but became an independent company once again in 1945. In 1949, it merged with Northern Arizona Power and Light. In 1952, it merged with Arizona Edison and changed its name to Arizona Public Service. The stock doubled in price through the long bear market of the 1970s, while paying a 10% dividend yield. By then it had become an electric and natural gas utility fueled 94.4% by coal