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What happens to the grid when the sun goes away?

Early April is typically a kind of goldilocks moment for solar power. Days are getting longer but the weather is still mild, meaning that higher solar power generation isn’t entirely eaten up by increased demand due to air conditioning.
But that all depends on the sun actually shining.
Monday’s solar eclipse took a big chunk of power off the grid. Since 2017’s eclipse, solar power generation has increased substantially, both locally (think rooftops) and at utility scale (think massive fields of solar panels). In 2017, the U.S. had around 35 gigawatts of utility-scale solar capacity, a figure that had increased to an estimated 95 gigawatts by the end of 2023.
While total solar eclipses are rare (the next one to hit the lower 48 isn’t expected until 2044), the challenges they present to grid operators may be part of the new normal. With vastly expanded renewable energy generation comes a greater degree of unpredictability, as a growing a portion of the generation fleet can drop off the grid due to weather and climate conditions — like, say, clouds of smoke from a wildfire — that cannot be precisely predicted by 17th century science.
Grid operators were confident they’d be able to manage through the eclipse without any reliability issues, and what actually transpired mostly confirmed their forecasts. In Texas, solar power production shrunk from around 13.5 gigawatts at noon, making up 27% of the grid’s electricity supply, to a mere 0.8 gigawatts at 1:30 p.m. Things did not go as well for the Midcontinent Independent System Operator, however, which includes a swath of the middle of the country from Minnesota to Indiana to Louisiana. Solar output was estimated to drop from around 4 gigawatts at 1 p.m. Central time to 2 gigawatts an hour later, according to Grid Status. Instead, output dropped to around 300 megawatts, causing real-time prices for power on the grid to spike.

Overall, the U.S. Energy Information Administration estimated that some 6,500 megawatts of solar generation capacity would be fully obscured during the eclipse, which would “partially block sunlight to facilities with a combined 84.8 GW of capacity in an even larger swath of the United States around peak solar generating time.” Some 40 gigawatts may have come off the grid, enough power for about 28 million homes, according to a release from Solcast, a solar forecasting company.
By comparison, during the 2017 eclipse, solar power loss at its peak was between 4 and 6.5 gigawatts and the total loss of power was around 11 gigawatts, according to the National Renewable Energy Laboratory.
In states like Texas, the main effect was on utility-scale production of solar, but in the Northeast and parts of the mid-Atlantic and Midwest, there was also a related problem: Behind-the-meter solar fell off, too, thus requiring the homes and businesses that generate power for themselves in the middle of the day to get more power from the grid, increasing demand on the grid at a time of low supply.
New England has seen immense growth in rooftop solar, and solar production was expected to fall by “thousands” of megawatts, according to ISO New England, while the New York Independent System Operators expected to lose 700 megawatts of behind the meter solar.
During the 2017 eclipse, the National Renewable Energy Laboratory found that “the burden of compensating for the lost energy from solar generators fell to the thermal fleet,” i.e. natural gas, along with some increases in coal and hydropower production.
Since then, the coal fleet has shrunk, thus putting more of the burden of responding to Monday’s eclipse onto gas and hydro, but the basic logic still applies. “Grid operators are expected to rely on natural gas to ensure stability and meet the household demand spike across national grids, as was done during the previous eclipse in 2023 in California and Texas,” according to Solcast. As the sun was dimming in Texas, natural gas generation rose from 18.7 gigawatts to 27.5 gigawatts.
Something else that’s changed since 2017: batteries. By the end of 2023, Texas had installed 5.6 gigawatts of grid storage, most of it providing so-called “ancillary services,” power sources that can respond quickly to immediate needs. ERCOT, the electricity market that covers most of Texas, said in a presentation back in February that it would rely on these ancillary tools to get through the eclipse, and once again, it was right. Power from batteries on the grid got up 1.4 gigawatts during the eclipse.
Editor’s note: This story has been updated to reflect the actual effects of the eclipse on U.S. power generation.
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There has been no new nuclear construction in the U.S. since Vogtle, but the workers are still plenty busy.
The Trump administration wants to have 10 new large nuclear reactors under construction by 2030 — an ambitious goal under any circumstances. It looks downright zany, though, when you consider that the workforce that should be driving steel into the ground, pouring concrete, and laying down wires for nuclear plants is instead building and linking up data centers.
This isn’t how it was supposed to be. Thousands of people, from construction laborers to pipefitters to electricians, worked on the two new reactors at the Plant Vogtle in Georgia, which were intended to be the start of a sequence of projects, erecting new Westinghouse AP1000 reactors across Georgia and South Carolina. Instead, years of delays and cost overruns resulted in two long-delayed reactors 35 miles southeast of Augusta, Georgia — and nothing else.
“We had challenges as we were building a new supply chain for a new technology and then workforce,” John Williams, an executive at Southern Nuclear Operating Company, which owns over 45% of Plant Vogtle, said in a webinar hosted by the environmental group Resources for the Future in October.
“It had been 30 years since we had built a new nuclear plant from scratch in the United States. Our workforce didn’t have that muscle memory that they have in other parts of the world, where they have been building on a more regular frequency.”
That workforce “hasn’t been building nuclear plants” since heavy construction stopped at Vogtle in 2023, he noted — but they have been busy “building data centers and car manufacturing in Georgia.”
Williams said that it would take another “six to 10” AP1000 projects for costs to come down far enough to make nuclear construction routine. “If we were currently building the next AP1000s, we would be farther down that road,” he said. “But we’ve stopped again.”
J.R. Richardson, business manager and financial secretary of the International Brotherhood of Electric Workers Local 1579, based in Augusta, Georgia, told me his union “had 2,000 electricians on that job,” referring to Vogtle. “So now we have a skill set with electricians that did that project. If you wait 20 or 30 years, that skill set is not going to be there anymore.”
Richardson pointed to the potential revitalization of the failed V.C. Summer nuclear project in South Carolina, saying that his union had already been reached out to about it starting up again. Until then, he said, he had 350 electricians working on a Meta data center project between Augusta and Atlanta.
“They’re all basically the same,” he told me of the data center projects. “They’re like cookie cutter homes, but it’s on a bigger scale.”
To be clear, though the segue from nuclear construction to data center construction may hold back the nuclear industry, it has been great for workers, especially unionized electrical and construction workers.
“If an IBEW electrician says they're going hungry, something’s wrong with them,” Richardson said.
Meta’s Northwest Louisiana data center project will require 700 or 800 electricians sitewide, Richardson told me. He estimated that of the IBEW’s 875,000 members, about a tenth were working on data centers, and about 30% of his local were on a single data center job.
When I asked him whether that workforce could be reassembled for future nuclear plants, he said that the “majority” of the workforce likes working on nuclear projects, even if they’re currently doing data center work. “A lot of IBEW electricians look at the longevity of the job,” Richardson told me — and nuclear plants famously take a long, long time to build.
America isn’t building any new nuclear power plants right now (though it will soon if Rick Perry gets his way), but the question of how to balance a workforce between energy construction and data center projects is a pressing one across the country.
It’s not just nuclear developers that have to think about data centers when it comes to recruiting workers — it’s renewables developers, as well.
“We don’t see people leaving the workforce,” said Adam Sokolski, director of regulatory and economic affairs at EDF Renewables North America. “We do see some competition.”
He pointed specifically to Ohio, where he said, “You have a strong concentration of solar happening at the same time as a strong concentration of data center work and manufacturing expansion. There’s something in the water there.”
Sokolski told me that for EDF’s renewable projects, in order to secure workers, he and the company have to “communicate real early where we know we’re going to do a project and start talking to labor in those areas. We’re trying to give them a market signal as a way to say, We’re going to be here in two years.”
Solar and data center projects have lots of overlapping personnel needs, Sokolski said. There are operating engineers “working excavators and bulldozers and graders” or pounding posts into place. And then, of course, there are electricians, who Sokolski said were “a big, big piece of the puzzle — everything from picking up the solar panel off from the pallet to installing it on the racking system, wiring it together to the substations, the inverters to the communication systems, ultimately up to the high voltage step-up transformers and onto the grid.”
On the other hand, explained Kevin Pranis, marketing manager of the Great Lakes regional organizing committee of the Laborers’ International Union of North America, a data center is like a “fancy, very nice warehouse.” This means that when a data center project starts up, “you basically have pretty much all building trades” working on it. “You’ve got site and civil work, and you’re doing a big concrete foundation, and then you’re erecting iron and putting a building around it.”
Data centers also have more mechanical systems than the average building, “so you have more electricians and more plumbers and pipefitters” on site, as well.
Individual projects may face competition for workers, but Pranis framed the larger issue differently: Renewable energy projects are often built to support data centers. “If we get a data center, that means we probably also get a wind or solar project, and batteries,” he said.
While the data center boom is putting upward pressure on labor demand, Pranis told me that in some parts of the country, like the Upper Midwest, it’s helping to compensate for a slump in commercial real estate, which is one of the bread and butter industries for his construction union.
Data centers, Pranis said, aren’t the best projects for his members to work on. They really like doing manufacturing work. But, he added, it’s “a nice large load and it’s a nice big building, and there’s some number of good jobs.”
A conversation with Dustin Mulvaney of San Jose State University
This week’s conversation is a follow up with Dustin Mulvaney, a professor of environmental studies at San Jose State University. As you may recall we spoke with Mulvaney in the immediate aftermath of the Moss Landing battery fire disaster, which occurred near his university’s campus. Mulvaney told us the blaze created a true-blue PR crisis for the energy storage industry in California and predicted it would cause a wave of local moratoria on development. Eight months after our conversation, it’s clear as day how right he was. So I wanted to check back in with him to see how the state’s development landscape looks now and what the future may hold with the Moss Landing dust settled.
Help my readers get a state of play – where are we now in terms of the post-Moss Landing resistance landscape?
A couple things are going on. Monterey Bay is surrounded by Monterey County and Santa Cruz County and both are considering ordinances around battery storage. That’s different than a ban – important. You can have an ordinance that helps facilitate storage. Some people here are very focused on climate change issues and the grid, because here in Santa Cruz County we’re at a terminal point where there really is no renewable energy, so we have to have battery storage. And like, in Santa Cruz County the ordinance would be for unincorporated areas – I’m not sure how materially that would impact things. There’s one storage project in Watsonville near Moss Landing, and the ordinance wouldn’t even impact that. Even in Monterey County, the idea is to issue a moratorium and again, that’s in unincorporated areas, too.
It’s important to say how important battery storage is going to be for the coastal areas. That’s where you see the opposition, but all of our renewables are trapped in southern California and we have a bottleneck that moves power up and down the state. If California doesn’t get offshore wind or wind from Wyoming into the northern part of the state, we’re relying on batteries to get that part of the grid decarbonized.
In the areas of California where batteries are being opposed, who is supporting them and fighting against the protests? I mean, aside from the developers and an occasional climate activist.
The state has been strongly supporting the industry. Lawmakers in the state have been really behind energy storage and keeping things headed in that direction of more deployment. Other than that, I think you’re right to point out there’s not local advocates saying, “We need more battery storage.” It tends to come from Sacramento. I’m not sure you’d see local folks in energy siting usually, but I think it’s also because we are still actually deploying battery storage in some areas of the state. If we were having even more trouble, maybe we’d have more advocacy for development in response.
Has the Moss Landing incident impacted renewable energy development in California? I’ve seen some references to fears about that incident crop up in fights over solar in Imperial County, for example, which I know has been coveted for development.
Everywhere there’s batteries, people are pointing at Moss Landing and asking how people will deal with fires. I don’t know how powerful the arguments are in California, but I see it in almost every single renewable project that has a battery.
Okay, then what do you think the next phase of this is? Are we just going to be trapped in a battery fire fear cycle, or do you think this backlash will evolve?
We’re starting to see it play out here with the state opt-in process where developers can seek state approval to build without local approval. As this situation after Moss Landing has played out, more battery developers have wound up in the opt-in process. So what we’ll see is more battery developers try to get permission from the state as opposed to local officials.
There are some trade-offs with that. But there are benefits in having more resources to help make the decisions. The state will have more expertise in emergency response, for example, whereas every local jurisdiction has to educate themselves. But no matter what I think they’ll be pursuing the opt-in process – there’s nothing local governments can really do to stop them with that.
Part of what we’re seeing though is, you have to have a community benefit agreement in place for the project to advance under the California Environmental Quality Act. The state has been pretty strict about that, and that’s the one thing local folks could still do – influence whether a developer can get a community benefits agreement with representatives on the ground. That’s the one strategy local folks who want to push back on a battery could use, block those agreements. Other than that, I think some counties here in California may not have much resistance. They need the revenue and see these as economic opportunities.
I can’t help but hear optimism in your tone of voice here. It seems like in spite of the disaster, development is still moving forward. Do you think California is doing a better or worse job than other states at deploying battery storage and handling the trade offs?
Oh, better. I think the opt-in process looks like a nice balance between taking local authority away over things and the better decision-making that can be brought in. The state creating that program is one way to help encourage renewables and avoid a backlash, honestly, while staying on track with its decarbonization goals.
The week’s most important fights around renewable energy.
1. Nantucket, Massachusetts – A federal court for the first time has granted the Trump administration legal permission to rescind permits given to renewable energy projects.
2. Harvey County, Kansas – The sleeper election result of 2025 happened in the town of Halstead, Kansas, where voters backed a moratorium on battery storage.
3. Cheboygan County, Michigan – A group of landowners is waging a new legal challenge against Michigan’s permitting primacy law, which gives renewables developers a shot at circumventing local restrictions.
4. Klamath County, Oregon – It’s not all bad news today, as this rural Oregon county blessed a very large solar project with permits.
5. Muscatine County, Iowa – To quote DJ Khaled, another one: This county is also advancing a solar farm, eliding a handful of upset neighbors.