American Electric Power Company, Inc. is an American domestic electric utility company in the United States. It is one of the largest electric utility companies in the country, with more than five million customers in 11 states. American Electric Power Company is one of the nation's largest generators of electricity, owning nearly 38,000 megawatts of generating capacity in the United States. AEP also owns the nation's largest electricity transmission system, a nearly 39,000-mile network that includes more 765 kilovolt ultra-high voltage transmission lines than all other U.S. transmission systems combined. AEP's transmission system directly or indirectly provides about 10 percent of the electricity demand in the Eastern Interconnection, the interconnected transmission system that covers 38 eastern and central U.S. states and eastern Canada, and approximately 11 percent of the electricity demand in the Electric Reliability Council of Texas, the transmission system that covers much of Texas. AEP's utility units operate as AEP Ohio, AEP Texas, Appalachian Power, Indiana Michigan Power, Kentucky Power, Public Service Company of Oklahoma, and Southwestern Electric Power Company.