Costs of recently completed improvements to Xcel Energy's Monticello nuclear power plant have jumped to $640 million, double what the utility had originally budgeted in 2008.
The most recent cost estimate was revealed in a filing made Wednesday with the Minnesota Public Utilities Commission, the Star Tribune reports.
The five-year project included replacing aging equipment and boosting electric output by 12 percent, the St. Cloud Times said. After a four-month shutdown, Xcel expects to restart the plant this month.
It was reported earlier this week that the project was significantly over budget.
The Star Tribune says Xcel wanted to keep the latest estimate, which was already submitted to the PUC in January, under wraps so vendors submitting their bills for work wouldn't know "how much contingency was built into the budget."
To pay for the cost overruns, Xcel has requested a 10.7 percent rate hike.
Jeanne Cochran, a state administrative law judge, found that Xcel's request was too high and recommended that the utility be allowed a rate increase of just 4.7 percent.
In April, the Minnesota Department of Commerce recommended only a 2-3 percent increase.
The PUC will make a final decision on rates this fall.