ST. PAUL — Legislation that would help Xcel Energy plan for the high costs of maintaining old nuclear power plants is heading to the Minnesota Senate, where it could face some tough opposition.

Republican Sen. Andrew Mathews of Milaca is sponsoring the bill, which would give utilities earlier notice about how much money they could recover for costly work, according to a press release.

Investor-owned utilities must submit multi-year plans to the state Public Utilities Commission that detail how much power the utility plans on generating. After the plan is approved, the utility funds repairs and maintenance for power plants. Customers then reimburse companies for those investments through rate increases if the utilities commission determines the investments were practical.

Xcel Energy hopes to keep its Monticello and Prairie Island nuclear plants operational for another 12 to 15 years. The bill would help the company predict how much money it will need to fund power plant maintenance.

Wind and solar sources aren’t yet able to completely replace the nuclear plants, said Chris Clark, Xcel’s president. The company is working toward having carbon-free sources generate 85 percent of its electricity by 2030.

Gov. Mark Dayton said Tuesday that he’s not interested in altering the current process.

“These end-runs through the Legislature to get special interests what they want violates the whole purpose of the Public Utilities Commission, which is to have an independent group of experts who make these determinations in the public interest,” he said.

Customers need better protection from cost overruns, said Annie Levenson-Falk, executive director of the Citizens Utility Board of Minnesota.

The Minnesota Chamber of Commerce, some manufacturers and several environmental groups also oppose the bill.