HELENA, Mont. (AP) — Montana utility regulators say NorthWestern Energy would have to pay about $20 per megawatt hour for electricity from a proposed 80-megawatt solar power project near Billings.

MTSun LLC had initially proposed a rate of nearly $64 and in late November rejected NorthWestern's offer of about $43.50. NorthWestern is required to buy power from such renewable facilities at a rate that it would otherwise cost the utility to generate the energy. If they can't agree on a rate, the Public Service Commission sets it.

The PSC authorized the 10-year contract on Thursday a week after vo...