In a $4.9 billion deal, Duke Energy Corp. said it would acquire Piedmont Natural Gas Co., the Wall Street Journal reported Monday. Duke Energy was expected to gain one million natural gas customers in the deal.

“We look forward to welcoming Piedmont’s employees and 1 million customers in the Carolinas and Tennessee to Duke Energy,” said Lynn Good, CEO of Duke Energy.

Duke Energy is the U.S.’s largest power company by generation capacity. The company offered $60 a share for Piedmont, according to Reuters. Piedmont’s shares were up 17 percent while Duke rose by 2 percent Monday. Duke will assume $1.8 billion in Piedmont debt.

The increase in American shale production in recent years has led power companies to add to their natural gas capacities. With increased energy efficiency, companies have chosen to focus on natural gas as electricity demands have weakened in the U.S. 

Piedmont and Duke have worked together in the past, partnering on the $5 billion Atlantic Coast Pipeline which moves gas from Pennsylvania to Virginia and North Carolina. Both companies have operated in the Carolinas for over 60 years, a news release from Duke Energy said.

"The strategic combination of our two companies will deliver compelling value to our shareholders, greatly expand our platform for future growth, enhance our ability to provide excellence in customer service and give our employees more opportunities in one of the largest energy companies in the United States," said Tom Skains, CEO of Piedmont Natural Gas.

News of the deal comes after Duke settled a $81 million lawsuit over energy rebates in Ohio.

Regulatory and shareholder approval were still required to finalize the Duke-Piedmont deal, but the two companies hoped to have final approval by the end of the 2016. When the deal is completed, Piedmont was expected to become a business unit within Duke Energy.