Constellation Energy Corporation ( CEG, Financials) said Friday that it will purchase Calpine Corporation ( CPN, Financials) for $26.6 billion in cash and shares, becoming the largest US renewable energy provider. The agreement combines Calpine's low-carbon natural gas and geothermal with Constellation's emissions-free nuclear.

CEG announces the acquisition of Calpine. This should help CEG provide a broader array of clean energy and sustainability solutions.

Baltimore-based Constellation, the nation’s largest operator of nuclear power plants, is acquiring Calpine Corp.