NASHVILLE (AP) - The country's largest public utility will rely more on natural gas and renewable energy in the future.

On Monday, the Tennessee Valley Authority released its integrated resource plan for the next 20 years. The plan is a roadmap of how the utility intends to respond in good or bad economic times or during periods of more environmental regulation.

No matter the scenario, TVA officials see the agency relying far more on natural gas and renewable energy, especially solar power. Environmental groups hailed it as a important first step but said TVA has not gone far enough.

TVA will hold a series of public meetings on the plan.

TVA serves 9 million people in parts of Tennessee, Alabama, Mississippi, Kentucky, Georgia, North Carolina and Virginia.