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, one of the biggest acquisitions in U.S. power industry history.

Constellation Energy’s deal to buy Calpine is being driven by fast-rising demand for electricity in part by the technology industry’s investments in artificial intelligence.