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.

Constellation Energy jumped Friday after announcing that it will buy Calpine, adding geothermal and more natural gas to its portfolio.

Constellation Energy struck a $26.6 billion deal to buy Calpine, uniting two of the U.S.'s largest power generators amid surging electricity demand from tech companies. Constellation shares rallied 3.