Exelon Corp. and Constellation Energy on Monday completed their long-awaited $7.9 billion merger. The combined company, which retains the Exelon name, has a market cap of $34 billion, a 35-GW generation fleet, and activity in 47 U.S. states and some Canadian provinces. It is now the biggest power utility in the U.S.—until the $26 billion Duke-Progress merger is completed, at least.

Upon closing the merger, Exelon’s Christopher Crane became president and CEO of the combined company while Constellation’s Mayo A. Shattuck III became executive chairman. The new company remains headquartered in Chicago, though it continues significant operations in Maryland, Illinois and Pennsylvania. It will trade on the New York Stock Exchange under the symbol EXC.

“The merged company is now one of the nation’s largest competitive energy products and services suppliers by load (about 164 terawatt-hours per year) and customers (approximately 100,000 business and public sector and approximately 1 million residential), serving more than two-thirds of America’s Fortune 100 companies,” the new company said in a statement on Monday.

Exelon’s total generation capacity is about 35 GW—more than 19 GW of which is nuclear power capacity. The three utilities within Exelon—BGE, ComEd and PECO—will remain headquartered in Baltimore, Chicago, and Philadelphia, respectively.

Since announcing the merger in May 2011, the transaction has been approved by shareholders of Exelon and Constellation and garnered required regulatory approvals or reviews from the Federal Energy Regulatory Commission (FERC), Maryland Public Service Commission, New York Public Service Commission, the Public Utility Commission of Texas, the Department of Justice, and the Nuclear Regulatory Commission.

When complete, Duke Energy’s merger with Progress Energy will create a giant company with a generation fleet of 57 GW. In late February, the companies said they would amend a proposal to the North Carolina Public Utilities Commission after FERC rejected the original plan in December. North Carolina regulators have as long as 30 days to review the filing before it is resubmitted to FERC.

Sources: POWERnews, Exelon Corp.