The company has also agreed to reduce the coal plants air emissions, preserve land nearby, and build some kind of green power source there.

Indianapolis Power & Light plans to close two of its four coal units at its Petersburg plant by 2023. But environmentalists say IPL needs to move away from coal more quickly.

The Petersburg Generating Station activists want to see closed is a coal-fired power plant in southwest Indiana. It's been in the news as what's called a "super polluter."

Pending regulatory approval, Indianapolis Power & Light says their customers will see about a $5 a month increase in their bills.

An Indianapolis Power & Light representative says the company wanted to know where customers opposed to the increase were coming from. But some say it was an attempt to discredit opponents.

IPL forecasts that the plant's capacity factor - or how often it can run - will increase to 70 percent next year. That's up from less than 60 percent in 2015.

Most IPL customers have to pay a fixed charge of $17 a month, but if the utility gets its wish that would jump to $27 a month.

IPL says it needs more money to cover operating expenses and revenues. Some say the company painted a different picture for shareholders just weeks before filing the request.

Indianapolis Power and Light seeks a rate hike to cover higher operating and maintenance costs and to cover the costs of the newly built Eagle Valley Generating Station in Morgan County.

As Indiana environmental regulators grapple with how to deal with the storage of coal ash at power generating stations, environmental groups push for tough standards.