Key for Constellation was gaining a larger slice of the Texas market, where electricity demand is expected to grow at one of the fastest rates, said Joe Dominguez, chief executive

The company is betting that data-center owners will be hungry for all sorts of power—from nuclear to conventional.

Constellation Energy is nearing a roughly $30 billion deal to acquire power producer Calpine, people familiar with the matter said on Wednesday, a move that would significantly expand Constellation's generation assets at a time of rising U.