The Energy Department says the U.S. needs to make it cheaper and easier to run power plants.

The agency on Wednesday said the country's electric grid would be strengthened if regulators eased the burdens on power plants, including coal and nuclear plants.

The department said in a new report that the closure of many plants that once formed the backbone of the grid has raised the risk that consumers might not have reliable electricity.

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In a letter accompanying the report, Energy Secretary Rick Perry said the U.S. is fortunate to have many sources of energy and should use them all.

In a key recommendation, the report urges the federal government to make licensing and permitting faster and cheaper for facilities "such as nuclear, hydro, coal, advanced generation technologies, and transmission."

Environmentalists and advocates for renewable energy have been bracing for the report since drafts that leaked to the press in recent weeks. They say the Energy Department will use the study to argue that fossil-fuel plants are needed to make the grid reliable, and that policies promoting renewables should be cut back.

Jim Marston, an official with the Environmental Defense Fund, said the Energy Department was "twisting facts to reach a predetermined conclusion in favor of coal." He said the agency ignored evidence from California that solar energy is reliable.

On the other side, the CEO of the American Coalition for Clean Coal Electricity praised the report. Paul Bailey said, "One of the biggest challenges is how to preserve the nation's coal fleet so it can continue supporting a reliable and resilient electricity grid."

The U.S. energy market has undergone dramatic changes in the past 15 years. About 15 percent of the generating capacity that existed in 2002 has been retired, including many coal-fired plants that were replaced by plants burning cheap natural gas. Natural gas replaced coal as the leading fuel for electricity in 2016.

Wind and solar power have also undermined coal and nuclear, the Energy Department report concluded. Helped by federal tax credits and favorable state policies, the department said, renewables have lower variable costs than so-called baseload plants — the coal and nuclear behemoths that steadily churned out electricity at high rates for many years.

The Energy Department report also heaped blame on environmental regulations. It said that the largest number of coal plant retirements occurred in 2015, the deadline for operators to install new pollution-control equipment.

Perry ordered the report back in April, saying a review of electricity reliability and markets was overdue.

In a cover letter to the 187-page report, Perry said, "We must utilize the most effective combination of energy sources with an 'all of the above' approach to achieve long-term, reliable American energy security." He has said that the Trump administration would pursue policies that promote reliable and affordable electricity from diverse energy sources.

President Donald Trump has vowed to revive the coal industry. The administration has rolled back some energy regulations, and Trump announced he will withdraw the U.S. from the Paris accord on controlling climate change.