ST. PAUL — Minnesota utility regulators are deciding between solar power and natural gas for providing additional electricity for Xcel Energy’s 1.2 million customers in the state.

At issue is whether Xcel Energy’s customers would be best served by $250 million in solar power arrays proposed by Geronimo Energy of Edina or by adding generating units at power plants in Burnsville, Cannon Falls or Mankato.

The commission is expected to decide the question Thursday.

An administrative law judge concluded three months ago that Xcel Energy’s power needs aren’t growing so fast. He recommended Geronimo Energy’s plan to build about 20 solar arrays next to Xcel substations as the best deal.