The settlement, which requires court approval, calls for the companies to sell three coal plants in Maryland to alleviate market concentration in the mid-Atlantic electricity grid. Exelon and Constellation already announced plans to divest the Brandon Shores and H.A. Wagner plants in Anne Arundel County and the C.P. Crane plant in Baltimore County.
Under the settlement, the Justice Department has the right to approve a buyer for those plants.
The $7.9 billion deal still requires approval by the Federal Energy Regulatory Commission, the Nuclear Regulatory Commission and the Maryland Public Service Commission, which will make a decision by Feb. 17.
The companies expect to close the deal in early 2012.