Ameren Missouri, the state’s largest electricity provider, has filed papers with the Securities and Exchange Commission claiming that it will lose $300 million if a court case stands.

Ameren is fighting a ruling by Cole County Circuit Judge Paul Wilson that it roll back rates to 2007 levels. The court over-ruled Public Service Commission rate increases approved in 2009. At the first of that year, the PSC approved an eight-percent rate increase for the St. Louis-based utility, allowing Ameren to reap $163 million more from customers. Later that year, the PSC approved another 10%, $226 million rate hike.

Noranda Aluminum, by far Ameren’s largest customer, filed suit along with the Office of Public Counsel in southeast Missouri’s Pemiscot County Circuit Court. Other large corporations followed suit after the second rate increase and the case moved to Cole County in Jefferson City.

A spokesman for Ameren expressed confidence that the utility in prevail and the rates will stand.