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 is buying power natural gas and geothermal power provider Calpine in a cash-and-stock deal valued at approximately $16.4 billion, joining together two of the country’s biggest power companies.