Why isn’t the U.S. electrical grid run on 100% renewable energy yet?

Generating electricity to power homes and businesses is a significant contributor to climate change. In the United States, one quarter of greenhouse gas emissions come from electricity production, according to the Environmental Protection Agency.

Solar panels and wind farms can generate electricity without releasing any greenhouse gas emissions. Nuclear power plants can too, although today’s plants generate long-lasting radioactive waste, which has no permanent storage repository.

But the U.S. electrical sector is still dependent on fossil fuels. In 2021, 61 percent of electricity generation came from burning coal, natural gas, or petroleum. Only 20 percent of the electricity in the U.S. came from renewables, mostly wind energy, hydropower and solar energy, according to the U.S. Energy Information Administration. Another 19 percent came from nuclear power.

The contribution from renewables has been increasing steadily since the 1990s, and the rate of increase has accelerated. For example, wind power provided only 2.8 billion kilowatt-hours of electricity in 1990, doubling to 5.6 billion in 2000. But from there, it skyrocketed, growing to 94.6 billion in 2010 and 379.8 billion in 2021.

That’s progress, but it’s not happening fast enough to eliminate the worst effects of climate change for our descendants.

“We need to eliminate global emissions of greenhouse gases by 2050,” philanthropist and technologist Bill Gates wrote in his 2023 annual letter. “Extreme weather is already causing more suffering, and if we don’t get to net-zero emissions, our grandchildren will grow up in a world that is dramatically worse off.”

And the problem is actually bigger than it looks.

“We need not just to create as much electricity as we have now, but three times as much,” says Saul Griffith, an entrepreneur who’s sold companies to Google and Autodesk and has written books on mass electrification. To get to zero emissions, all the cars and heating systems and stoves will have to be powered with electricity, said Griffith. Electricity is not necessarily clean, but at least it it can be, unlike gas-powered stoves or gasoline-powered cars.

The technology to generate electricity with wind and solar has existed for decades. So why isn’t the electric grid already 100% powered by renewables? And what will it take to get there?

First of all, renewables have only recently become cost-competitive with fossil fuels for generating electricity. Even then, prices depend on the location, Paul Denholm of the National Renewable Energy Laboratory told CNBC.

In California and Arizona, where there is a lot of sun, solar energy is often the cheapest option, whereas in places like Maine, solar is just on the edge of being the cheapest energy source, Denholm said. In places with lots of wind like North Dakota, wind power is cost-competitive with fossil fuels, but in the Southeast, it’s still a close call.

Then there’s the cost of transitioning the current power generation infrastructure, which was built around burning fossil fuels.

“You’ve got an existing power plant, it’s paid off. Now you need renewables to be cheaper than running that plant to actually retire an old plant,” Denholm explained. “You need new renewables to be cheaper just in the variable costs, or the operating cost of that power plant.”

There are some places where that is true, but it’s not universally so.

“Primarily, it just takes a long time to turn over the capital stock of a multitrillion-dollar industry,” Denholm said. “We just have a huge amount of legacy equipment out there. And it just takes awhile for that all to be turned over.”

The transmission system in the U.S. is built for the electricity capacity that is already on the grid, and building new transmission lines that run hundreds of miles can take anywhere from 10 to 15 years, John Moura, the director of reliability assessment at the North American Electric Reliability Corp., told CNBC. “The type of transmission we’re talking about here are 1,000 [or] 2,000 miles long, large projects.”

Currently, when a utility wants to add electricity to the existing grid, it has to pay for the upgraded transmission line and for the interconnection, which is where multiple local grids are brought together. Those grid upgrades are expensive, and the permit process is slow.

Several components of the Infrastructure Investment and Jobs Act signed in November 2021 gave the Federal Energy Regulatory Commission much stronger permitting authority, transmission line analyst Rob Gramlich told CNBC. Still, some key rule changes did not get across the finish line. There was no transmission tax credit included in this year’s Inflation Reduction Act, and efforts by Sen. Joe Manchin, D.-W.Va., to reform permitting have so far failed to pass.

“Transmission was not meaningfully addressed in the 117th Congress. There is a lot of unfinished business on the transmission front, for sure,” Gramlich told CNBC.

Putting transmission lines underground is another option, but that’s prohibitively expensive.

“Your classical old-school, large overhead transmission lines are pretty much the only thing that we are likely to see at least in the next decade or two,” Denholm said.

But “that is definitively not the challenge,” Moura said.

It would take a total of 0.84 percent of U.S. land to support an entirely renewable-powered energy system, Stanford professor Mark Jacobson told CNBC. By comparison, the fossil fuel industry takes up 1.3 percent of U.S. land.

“Offshore wind, tidal, and wave power do not take up any new land. Rooftop photovoltaic does not take up any new land,” he said.

So really, the only new land required would be for solar facilities run by utilities, and for wind turbines on land.

But many people are reluctant to embrace a new way of doing things when they can’t see what the future will look like, and when maintaining the status quo is the path of least resistance, according to Griffith, the mass-electrification advocate

“The biggest barrier is a lack of imagination,” Griffith told CNBC in a video interview from Australia, where he currently lives. “So everyone is like, ‘Well, I’m not quite willing to do this, because I don’t know what it’s going to look like. And maybe it’s going to be terrible.'”

So what would a 100% renewable-powered world look like, according to Griffith?

“It’s going to look like every house has solar on its roof. There’ll be solar over every parking structure. Some roads will probably have a solar panels elevated down the middle of the road. And every time you go driving in the countryside, you’ll see some wind somewhere on the horizon,” Griffith said.

“And otherwise, the future is going to look a lot like it does.”