The deal will create the largest low-emission energy supplier in the United States, the companies said, amid rising energy needs fueled by the artificial intelligence boom.

Baltimore-based Constellation will pay approximately $16.4 billion in cash and shares and assume Calpine's debt, the companies said in a joint statement.

Calpine, a leader in low-emission natural gas production in the United States, owns 79 facilities, including the largest US geothermal energy site in northern California.

"By combining Constellation's unmatched expertise in zero-emission nuclear energy with Calpine's industry-leading, best-in-class, low-carbon natural gas and geothermal generation fleets, we will be able to offer the broadest array of energy products and services available in the industry," Constellation CEO Joe Dominguez said in the statement.

Constellation and Calpine will have a combined capacity of 60 gigawatts from zero- or low-emission sources, including nuclear, natural gas, geothermal, hydroelectricity, wind, solar, cogeneration and battery storage, according to the statement.

The deal will expand Constellation's footprint in the United States, particularly in Texas, a market with rapidly growing electricity demand, as well as in other strategic states, such as California, Delaware and Virginia.

The deal comes as companies seek energy sources to fuel their rapidly expanding AI operations while seeking to uphold low-carbon emission commitments.

Globally, data centers account for only one percent of global electricity consumption, according to the International Energy Agency.

But in some places, demand is booming. In 2023, data centers were responsible for a quarter of energy consumption in the southeastern US state of Virginia, the agency said.

In September, Constellation announced it would restart operations at Three Mile Island power plant to supply electricity to Microsoft.

Constellation Energy was previously a subsidiary of Chicago-based Exelon, but spun off in 2022.