Sioux Falls, SD-based NorthWestern Corp.'s Montana utility operations were granted electricity and natural gas interim retail rate increases by the state regulatory commission, the utility said Friday. The new rates were effective on Thursday.

Applied for last October, most of the utility increase request was granted on an interim basis by the Montana Public Service Commission (PSC) -- $12.39 million annually for electric customers and $1.36 million annually for natural gas customers. NorthWestern said it expects the PSC to issue a final order in the case in the fourth quarter. It originally had asked for $15.5 million, or 3.35%, for power rates and $1.96 million, or 0.10%, for gas.

The PSC's interim order indicated that if the final decision has a revenue requirement that is lower than the revenue increases granted on an interim basis, the difference will be refunded to retail utility customers at that time, plus interest of 10.75%, which is the amount of the utility's current authorized return on equity. "In addition, interim approval of any matters in this proceeding should not be viewed as final endorsement by the PSC of any issues, calculations or methodologies approved in the interim order," NorthWestern said.

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