Constellation is buying natural gas and geothermal power provider Calpine for $16.4 billion, joining together two of the country's biggest power companies. The acquisition would create the nation’s leading retail electric supplier,

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.

Constellation Energy Corp., an electricity provider whose stock has doubled over the last year on hopes it will help meet the voracious energy demand created by artificial-intelligence technologies, on Friday reached a $16.