Constellation Energy (CEG +6.36%) is the country's largest producer of carbon-free energy. That's largely due to its leading fleet of nuclear energy plants. The company also has a diverse mix of hydro, wind, and solar energy assets. Overall, Constellation powers more than 20 million homes and businesses, with 90% of its generation coming from carbon-free energy sources.
The company took a big step toward enhancing its already leading clean energy position in early 2025 by agreeing to acquire Calpine in a $26.6 billion deal. The transaction will create the country's largest clean energy provider, adding Calpine's natural gas, geothermal, and battery storage fleet to its portfolio. Those assets supply baseload power to help mitigate the intermittency of renewable energy.