Xcel Energy will continue to burn coal at its largest power plant in the Upper Midwest, the Sherburne County power plant near Becker. The Associated Press reports that Xcel clarified its position in a report to regulators. Xcel said that until environmental regulations become more clear, sticking with coal rather than switching to natural gas makes economic sense. Jim Alders, the consultant for Xcel, said the energy company evaluated the cost of building a series of natural gas plants as well as a combination of renewable energy and natural gas plants. The coal-burning Sherco 1 and 2 Units, which produce about 20 percent of the electricity used in Minnesota, compared favorably, he said. The two units came online in the 1970's. It would cost about $1.7 billion to replace them with cleaner-burning natural gas equipment. Installing pollution control equipment in them would cost nearly $400 million. Either change would raise customer rates.