Exelon Corp. would become the nation's largest electric utility company if its proposed merger with Pepco Holdings Corp. goes through, according to a ranking provided Monday by the U.S. Energy Information Administration.

Exelon, the parent company of Peco Energy Co. in Philadelphia, would have 8.6 million electric customers nationwide after the merger with Pepco, which operates utilities in Washington D.C., South Jersey and Delaware. Duke Energy Corp. would rank second with 7.2 million customers, followed by First Energy Corp. with 6 million, American Electric Power Co. Inc. with 5.3 million, and PG&E Corp. in northern California with 5.1 million.

Exelon, which is holding its annual meeting Tuesday in Philadelphia, announced the $6.8 billion merger with Pepco last week.