Constellation Energy agreed to buy Calpine for $16.4 billion, combining two of the country’s largest electricity generators at a time when their product is in high demand from tech companies. Including the assumption of debt,

U.S. nuclear power provider Constellation Energy on Friday agreed to buy privately-held natural gas and geothermal company Calpine Corp for $16.4 billion, marking one of the biggest acquisitions in the history of the U.

Constellation Energy — the electricity provider whose stock has doubled over the last year on hopes it’ll help meet the voracious energy demand from artificial intelligence — reached a $16 billion deal to buy Calpine.