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 is one of the best S&P 500 stocks Friday after the utility said it will buy Calpine in a cash-and-stock deal valued at $26 billion.

America’s largest nuclear power plant operator has agreed to buy Texas-headquartered geothermal and natural gas producer Calpine in a $26.6 billion which includes both cash and stock components. The deal highlights the role that natural gas is likely to play in meeting fast-rising US electricity demand.