Xcel Energy Inc., through its subsidiaries, engages in the generation, purchasing, transmission, distribution, and sale of electricity in the United States. It operates through Regulated Electric Utility and Regulated Natural Gas Utility segments. The company generates electricity through wind, nuclear, hydroelectric, biomass, and solar energy sources, as well as coal, natural gas, oil, wood, and refuse-derived fuels. It also purchases, transports, distributes, and sells natural gas to retail customers, as well as transports customer-owned natural gas. In addition, the company develops and leases natural gas pipelines, and storage and compression facilities; and invests in rental housing projects and nonregulated assets, as well as procures equipment for the construction of renewable generation facilities. It serves residential, commercial, and industrial customers in the portions of Colorado, Michigan, Minnesota, New Mexico, North Dakota, South Dakota, Texas, and Wisconsin. Xcel Energy Inc. was formerly known as Northern States Power company. The company was incorporated in 1909 and is headquartered in Minneapolis, Minnesota.