Black Hills Energy wants to raise rates for natural gas service to all its customers across Wyoming.

For residential customers, the proposed increase would be as low as 3.41% in Cody and as high as 71.49% for one division in Gillette, though the latter increase would affect a relatively small number of customers.

Casper residents would see an average proposed increase of $10.83 per month, or 21.51%, making the average bill $61.18.

Expected impact on residential and small general service customer bills from the Black Hills Energy application. Document available from the Wyoming Public Service Commission at dms.wyo.gov.

Bryce Freeman, administrator of the Wyoming Office of Consumer Advocate, told K2 Radio News on Monday that his staff is planning a trip to audit company records. It's a standard move when this sort of rate hike is proposed.

Freeman said that at first blush, no part of the application stood out as atypical. He called it a "pretty standard rate case," explaining that the increases appear to have been proposed largely to cover investments made by the company in areas such as infrastructure.

For example, the significant rate increase for customers in the Gillette area follows the company's efforts to improve a natural gas pipeline which had previously been exposed above-ground.

The company, Freeman added, has acquired a number of utilities across the state in recent years. Black Hills Energy serves roughly 129,500 customers in Wyoming.

The company operates Cheyenne Light, Fuel and Power Company (Cheyenne Light); Black Hills Energy as a division of Cheyenne Light, Fuel and Power Company (NEWY); Black Hills Northwest Wyoming Gas Utility Company, LLC (NWWY); and Black Hills Gas Distribution, LLC (BHGD-WY).

While NWYY saw a rate review just last year, BHGD-WY rates were last reviewed in 2011. Rates for NEWY customers have remained unchanged since 2012, and Cheyenne Light has not had a general rate review since 2014, according to the company's application.

Longer periods between reviews generally mean larger rate adjustments, Freeman said, as improvements are made, the natural gas market shifts and other factors change.

Should it be approved by the commission, the proposal would allow Black Hills Energy to increase its annual revenue by 17.28%, or $16,121,638. That would raise its total annual revenue to $86,372,534.

The Wyoming Public Service Commission will conduct a required investigation, according to a June 4 order. The company, in its application dated June 3, requested a four-day hearing on the rate hike be set for Dec. 16-20.

Customers who wish to formally intervene in the process or file a written statement, protest or request or public hearing must make their submission to the commission no later than July 19. Anyone who would like to make their voice heard in a less formal manner can contact the commission or Freeman's office.