Dynegy Inc. (NYSE: DYN) is buying five power plants from an Ameren (NYSE: AEE) subsidiary.

Dynegy is buying Ameren Energy Resources and its subsidiaries Ameren Energy Marketing Co., Ameren Energy Generating Co. and AmerenEnergy Resources Generating Co.

The company is making the purchase through its subsidiary, Illinois Power Holdings LLC. It won’t make a payment, but will take on $825 million in debt obligations.

Before the deal closes, Ameren will buy Ameren Energy Generating’s Elgin, Grand Tower and Gibson City natural-gas plants for $133 million.

The deal will give Dynegy more than 8,000 megawatts of generating capacity in Illinois. The company produces coal and gas-fired energy.

Dynegy’s holding company, Dynegy Holdings, exited from Chapter 11 bankruptcy protection in October, after restructuring its debt and merged into Dynegy Inc. (OTC: DYNIQ) when a New York bankruptcy judge confirmed its reorganization plan

The company filed for bankruptcy in the Southern District of New York on Nov. 7, 2011 after low electricity prices hurt profits.

Lazard is acting as Dynegy’s financial adviser.