Voters in Boulder, Colo., narrowly backed the creation of a municipal power authority to replace Xcel Energy Inc., the biggest electricity provider in Colorado. The city can't cut all ties with Xcel right away. The shift to a municipal utility will take at least three years and could be derailed over issues such as how much Boulder will pay Xcel for its infrastructure. Supporters of the move argue that a public utility would allow Boulder, a liberal college town, to embrace renewable energy and sharply reduce carbon emissions. Xcel relies heavily on coal-fired plants. Xcel spent nearly $1 million to try to defeat the Boulder ballot measures, outspending supporters about 10 to 1. People like a David-and-Goliath story, and that's absolutely what this is," said Ken Regelson, who led a community group supporting a public utility. Nationwide, 16 new public power authorities have been formed in the last decade, including 13 that have taken over from private utilities. Nearly all serve communities of less than 10,000, said Ursula Schryver, a vice president of the American Public Power Association, a trade group. Boulder's population is nearly 100,000. The last large-scale municipalization took place in 1998, on New York's Long Island.