Xcel Energy Inc. (Xcel) is a holding company, with subsidiaries engaged in the utility business. During the year ended December 31, 2007, Xcel Energy operations included the activity of four wholly owned utility subsidiaries that serve electric and natural gas customers in eight states. The utility subsidiaries are National States Power Company, Minnesota (NSP-Minnesota), National States Power Company, Wisconsin (NSP-Wisconsin), Public Service Company of Colorado (PSCo) and Southwestern Public Service Co., Mexico (SPS). The utilities serve customers in portions of Colorado, Michigan, Minnesota, New Mexico, North Dakota, South Dakota, Texas and Wisconsin. Along with WYCO Development LLC, (WYCO) a company formed to develop and lease new natural gas pipeline and compression facilities, and WestGas Interstate, Inc., Colorado (WGI), an interstate natural gas pipeline company, these companies comprise the continuing regulated utility operations.