HELENA, Mont. -

Montana utility regulators have granted a NorthWestern Energy request to boost electricity rates by 6.44 percent so the company can recover $32 million in underestimated supply costs.
    
The increase takes effect July 1.
    
Public Service Commission members said in approving the hike Tuesday the increase is temporary for now and whether it stays will be contingent on further study. The money can be returned if commissioners find they weren't justified.
    
NorthWestern has said its rates didn't reflect the actual market costs for the past 12 months. Over that period, one of the Colstrip power plant's units was offline for about six months.
    
The company has not said how much of the $32 million it is trying to recover is due to the outage. PSC staff estimated it cost $11 million.