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 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.

Separately, Calpine and Constellation are already among the largest power generation companies in the country.