KNOXVILLE (AP) — The Tennessee Valley Authority board of directors has approved a 20-year plan that includes no new major generating plants.

The Chattanooga Times Free Press reports the plan approved last week envisions getting more power out of existing nuclear, gas and hydroelectric units. It also includes more solar, backed up by improved energy storage and other new technologies.

TVA will also continue studying the possibility of building small modular nuclear reactors.

Environmental groups are disappointed with the plan. The Southern Environmental Law Center's Amanda Garcia says it doesn't do enough to encourage rooftop solar and efficiency.

She says, "TVA is missing a huge opportunity to chart a different course."

TVA is the nation's largest public utility, providing power to more than 10 million people in parts of seven Southern states.