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 8.

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.

Constellation Energy Corp. agreed to acquire closely held Calpine Corp. for $16.4 billion to add scores of power generation assets across the US as the nation’s electricity demand is forecast to surge.