Voters in Boulder, Colo., narrowly passed a measure Tuesday to replace Xcel Energy Inc. and allow the city to start a municipal electric utility.

The vote came after the collapse this summer of talks in which Xcel sought a 20-year extension of its franchise agreement and offered to boost the amount of electricity supplied from renewable sources like wind power.

Xcel, which is already a big producer of wind electricity, argued that it was in the best position to help Boulder meet ambitious renewable goals. Its plan aimed to supply 70 percent of the city's power from renewable sources within a year.

But Tuesday's vote means the city of 97,000 will continue to explore going on its own.

The vote was 51.8 percent in favor of the ballot measure, which was contested by Minneapolis-based Xcel. Voters in the city 30 miles north of Denver also narrowly approved a $1.9 million utility tax increase to begin the shift, according to unofficial results released early Wednesday.

The ballot measure authorized a municipal utility only if it can offer the same rates and service as Xcel. Boulder's City Council has not yet voted to form an electric utility, and the city manager's office said the process could take three to five years.

The city and Xcel are far apart on what price Boulder must pay for the utility's assets in the city.

"Although we are disappointed in the outcome, we know this is just the first step in a long process," Xcel CEO Ben Fowke said in a statement. "The costs to municipalize have been significantly understated by Boulder."

Fowke said the company is skeptical that the city will be able to match Xcel's rates or the level of renewable energy it supplies.

Xcel supplies power across eight states including most of Colorado.

City Manager Jane Brautigam said she recognized that the vote was close. "There are still a lot of questions and concerns that we need to address," she said, pledging to move ahead "in a deliberate, but measured, thoughtful and inclusive way."

In a statement, her office said city officials will reach out to businesses, large utility customers and community members who spoke out against forming a local electric utility.

David Shaffer • 612-673-7090