But like other Sanders energy plans — such as his proposal to reshape federal power regulations — his campaign insists changes to government-owned utilities could be pushed through Congress’s budget reconciliation process, which lawmakers used to enact the Affordable Care Act and requires only a simple majority vote. If that fails, Sanders could use the president's power to declare a national emergency on climate, which would give him broad authority to reshape the utilities but would likely be challenged in court.

Established under President Franklin Roosevelt’s New Deal, the power marketing administrations were created to close a divide in U.S. electricity access that persisted into the 1930s. By forming utilities like the Tennessee Valley Authority and the Bonneville Power Administration, the government financed the electrification of poor, remote communities where private utilities saw little opportunity for profit.

The Sanders plan comes amid an uptick in progressive groups' calls to expand public power. Climate activists from the Democratic Socialists of America have called for San Francisco to take over parts of Pacific Gas and Electric, the investor-owned utility that declared bankruptcy last year as it faced billions in liabilities for multiple deadly California forest fires. In Chicago, activists are pushing the city to split from the nuclear-heavy utility Exelon, and in Maine, Gov. Janet Mills signed a bill last summer directing state regulators to study forming a public power group.

In the past, public power campaigns, including a years'-long push to create a municipal utility in Boulder, Colo., have run aground over disputes about purchasing utility lines and power plants from their owners. But the Sanders' campaign says its proposal differs in a critical way: It would not make the government purchase power plants from existing utilities — it would build new renewable energy to compete with them.

“It is a hybrid plan and it harkens back to the original New Deal where they created these [federal utilities], and they were about lowering the cost of energy for consumers and having cooperative relationships with municipally or publicly owned utilities,” said Johanna Bozuwa, co-manager of the climate and energy program at the progressive think tank The Next System Project. “That creates more incentive and more potential for states, cities and regions that are trying to take over their power supplies. They know they have this option of cheap renewable energy.”

Power lines deliver electricity to rural Orange County near Hillsborough, N.C., in August 2018. | Gerry Broome/AP Photo

Energy analysts, however, caution that Sanders’s 2030 plan would require a federal infrastructure investment not seen since the construction of the interstate highway system. To get close to Sanders' 100 percent clean energy goal by 2030, researchers estimate the U.S. would need to add about 800 GW of wind and solar resources — about 25 times the amount the federal government expects to be built this year — along with ample amounts of battery storage and transmission. The Sanders camp forecasts that would cost about $2 trillion.

“Our best year for solar and wind — we’d have to multiply that by three and then sustain it for the next decade,” said Sonia Aggarwal, vice president at the analysis firm Energy Innovation, which advises world governments on their climate targets.

While turning the power grid over to 100 percent renewables presents significant technical difficulties, the clean energy deployment is "not out of the question," Aggarwal said. However, Sanders' plan to shut down nuclear power plants will make it “much more difficult.” The nation’s 60 nuclear plants generated more than half of U.S. carbon-free energy last year, but the Sanders campaign says it will phase them out by denying extensions of their operating licenses when they expire.

Many of those nuclear plants have licenses that expire after 2030, but Sanders expects the cheaper solar and wind power to drive most them into retirement. The stability those reactors provide to the power grid would be hard to replace with the variable output of the renewables, said Leah Stokes, assistant professor of political science at the University of California Santa Barbara.

“I feel like his plan does not grapple with the modeling that suggests 100 percent renewables is very expensive and very technically difficult,” Stokes said. “You can get to maybe 80 percent renewables easily, but I don’t think you can get to 100 percent that easily by 2030 … [and] if you compare to a situation where the nuclear energy stays open and you added all those renewables, then you’d have even more clean energy.”

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For Sanders allies, the call to scale up renewable energy so quickly is a major reason to support their plan. If the federal government doesn't intervene, they say, the private market won’t deliver the needed wind and solar growth quickly enough to combat climate change.

"We have done this type of scale before," said Bozuwa. "The Rural Electrification Administration, which was largely based on cooperative and public ownership, electrified a massive amount of the country in 10 years and that is the type of scale that we’re talking about here.”

Critics contend that the existing federal utilities may not be up to the task. Today, the Tennessee Valley Authority still generates about half its power from coal and is in the top-ten of carbon emitting U.S. utilities. The four western power marketing administrations get most of their energy from hydropower dams, but many are also skeptical they are ready to undertake a massive renewable energy build-out.

Instead of relying on those agencies, Stokes and Wood said Sanders could achieve the same goal with a national renewable energy standard that would force private utilities to buy renewable energy from private suppliers. In that case, the federal utilities could be used to build only the riskiest projects the private companies won't touch.

“I could see the benefit of having the federal government take on riskier, longer term projects that are needed for grid stability like concentrating solar power projects and pumped hydro,” Stokes said, “which probably is not how they’re thinking about it.”