Located: Monticello, Minn., 45 northwest of the Twin Cities.
Owner: Xcel Energy.
Online: 1970.
Type: GE boiling water reactor.
Output: 600 megawatts, enough to serve 500,000 homes; now capable of 671 megawatts.
Upgrade: Completed in July, replacing and upsizing major components to extend plant’s life and boost output by 12 percent.
License: Operating license expires in 2030 under a 20-year extension from the U.S. Nuclear Regulatory Commission; awaiting final approval to run at higher output.
Overruns: Upgrade costs more than doubled during five-year project to $665 million. Xcel must prove costs were prudent in order to charge ratepayers.