The ratings on Exelon Generation Co. LLC, a unit of Exelon Corp., are on CreditWatch with negative implications in response to the announced merger between Exelon and Public Service Enterprise Group Inc. (Enterprise). If completed, the merger will create the largest utility holding company in the U.S. Chicago, Ill.-based Exelon has about $10 billion in debt outstanding, net of stranded-cost securitization bonds. Similarly, Newark, N.J.-based Enterprise has about $10 billion in outstanding debt, net of stranded-cost securitization bonds. Standard&Poor's expects to resolve the CreditWatch listings on or near the completion of the merger after reviewing the business strategy and financial risk profile of the newly combined entity. The transaction is subject to approval from various state and federal