Calpine Corp

NRG Energy is a US-based integrated retail electricity and wholesale power-generation firm. The company has 2.5 million residential customers across the US.

Exelon Corporation’s (EXC) stock has been hammered in the last six years. In 2008, the stock was trading at ~$90 per share. Early this year, the stock was available at less than $27 per share.

In recent years, Duke Energy (DUK) made its intent very clear. It concentrates on its regulated utilities—its core business—instead of other areas. The regulated utilities business is Duke’s strength.

NextEra Energy is a Florida-based power company. Its subsidiaries are Florida Light & Power and NextEra Energy Resources.