This is the final regulatory approval required to close the transaction.

The merger is expected to create a combined company with a diversified energy delivery business and stronger generation portfolio, which will enhance customer service and operational flexibility.

Together, the companies will include ten electric distribution utilities serving six million customers; about 24,000MW of generating capacity; 67,000 square miles of service territory with operations in seven US states; about $48bn in assets; and $16bn in annual revenues.

Allegheny Energy owns and operates generating facilities and delivers electric service to over 1.5 million customers in Pennsylvania, West Virginia, Maryland and Virginia.

FirstEnergy is a diversified energy company headquartered in Akron, Ohio.