JACKSON, Miss. (AP) — Mississippi Power Co. customers will see electricity rates go up about 9 percent starting in September, a difference likely to mean more than $11 a month to a typical residential customer.

The state Public Service Commission on Tuesday approved general rate increases as well as specific increases tied to environmental compliance costs. The unit of Atlanta-based Southern Co. will collect about $77 million more through the end of 2019, in an agreement meant to cover 2018 and 2019.

A residential customer who uses 1,000 kilowatt hours of electricity per month would see bills rise from $128 monthly to more than $139 monthly. Most residential customers use more than that much electricity.

Mississippi Power also agreed that the three-member regulatory commission could delay a series of more expensive demands until a general rate case. The company is supposed to file its proposal for a modified rate structure in 2019, with a decision likely in 2020.

The company also agreed to not ask for any more increases in environmental and overall rates through 2020. In exchange, the company will collect two years' worth of revenue over 16 months, meant to make up for the failure to act for much of 2018.

"This will be our first base-rate adjustment since 2013," Mississippi Power CEO Anthony Wilson said in a statement. "It provides our business with the infusion of resources needed to continue to provide the safe and reliable energy our customers need to power their lives, homes and businesses."

Still, commissioners expressed displeasure at Mississippi Power's prices.

"I'm going to give you the feedback I've gotten from the people of the Southern District," said that district's Republican commissioner, Sam Britton. "The cost is high. Rates matter."

In 2016, residential customers of Mississippi Power paid the third-highest rate for electricity of 45 private, cooperative and municipal utilities tracked by the U.S. Energy Information Administration. Still, the rate remained below national averages.

Britton and Central District Commissioner Cecil Brown, a Democrat, both said they felt locked into granting the increase by Mississippi Power's formula-driven rate plan. Both expressed eagerness to begin an overall rate case.

Company officials had said the rate increase was merited in part to rebuild Mississippi Power's credit rating after a series of downgrades during the construction of the $7.5 billion Kemper County power plant. Regulators and the company finally agreed earlier this year that ratepayers would cover $1.1 billion of Kemper costs, while Mississippi Power absorbs $6.4 billion in losses.

The commission had granted smaller increases in May to pay for property taxes and energy efficiency programs, but held up Mississippi Power's larger requests for months.

The logjam broke last month when the company and the Public Utility Staff, a separate agency, reached an agreement. Regulators did win some concessions. For example, the company agreed to withdraw a request for $3.3 million in corporate airplane costs.

"It's symbolic of where the commission is trying to get to," said Northern District Commissioner Brandon Presley, a Democrat.

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