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MONTGOMERY, Ala. (AP) — Environmental groups and homeowners have filed a federal lawsuit against state regulators for approving Alabama Power’s fees on customers that have solar panels on their rooftop or on their property.

The Southern Environmental Law Center and Ragsdale LLC filed the lawsuit Monday against the Alabama Public Service Commission on behalf of the Greater-Birmingham Alliance to Stop Pollution (GASP) and four Alabama Power customers who installed solar panels on their properties.

Homeowners and an environmental groups argue that the fees purposely discourage residents to convert to solar energy in the sun-rich state.

FILE – In this Thursday, Nov. 14, 2019 file photo, Teresa Thorne walks out of her solar power-equipped home near Springville, Ala. The fees imposed by the Alabama Power company on customers who generate their own electricity with rooftop or on-site solar panels are now the subject of a federal lawsuit against the state’s regulators. Environmental groups argue that punishing fees are purposely discouraging the adoption of solar power in the sun-rich state. (AP Photo/Jay Reeves, File)

The amount of the fee is based on the various sizes of solar panels, but a typical rooftop installation of 4-6 kilowatts could add cause a customer’s electric bill to rise as much as $21 to $32 every month.

Alabama Power has maintained the fee is needed to maintain the infrastructure that will provide backup power to customers when the solar panels don’t provide enough energy.