The purpose of this publication is to provide year-end statistics about electric generating units operated by electric utilities in the United States (the 50 States and the District of Columbia). The publication also provides a 10-year outlook of future generating unit additions. The Summary Statistics chapter contains aggregate capacity statistics at the national and various regional levels for operable electric generating units and planned electric generating unit additions. Aggregate capacity data at the national level are presented by energy source and by prime mover. Aggregate capacity data at the various regional levels are presented by prime energy source. Planned capacity additions in new units are summarized by year, 1991 through 2...