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.

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.

Constellation Energy said on Friday it would buy privately held Calpine Corp, a geothermal and natgas energy company, in a cash-and-stock deal valued at $26.6 billion including debt, sending Constellation's shares up 3.