Sign In or Create an Account.

By continuing, you agree to the Terms of Service and acknowledge our Privacy Policy

Climate

The Eclipse Was a 3-Hour Boon for Gas, Batteries, and Hydro

What happens to the grid when the sun goes away?

An eclipse and solar panels.
Heatmap Illustration/Getty Images

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.

ERCOT energy mix chart.ERCOT’s fuel mix from Monday, April 8, including during the solar eclipse.ERCOT

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.

Blue

You’re out of free articles.

Subscribe to access Heatmap’s expert analysis of energy, climate change, and sustainability, including coverage of our regular survey research. Save $57 on an annual subscription, just $156 $99/year.
To continue reading
Create a free account or sign in to unlock more free articles.
or
Please enter an email address
By continuing, you agree to the Terms of Service and acknowledge our Privacy Policy
Politics

Americans Still Love the Environment

Heatmap’s latest poll adds urgency to one of the biggest questions facing the climate: Can the environmental movement come back?

An old photograph.
Heatmap Illustration/Getty Images

Three years ago, I wrote a piece for this website about how I’d stopped openly describing myself as an environmentalist. Looking back at it now, it’s a bit of a head-scratcher: I love nature, conservation, and all things outdoorsy, and while I stand by my greater point — that we can’t let uncompromising ideals about the environment hold back renewable energy development — the truth is, I am absolutely an environmentalist. But saying so felt analogous to calling myself tender-hearted, naïve, and retrograde.

The truth is, most Americans are environmentalists, at least if you take a wide definition. In new polling and focus group research conducted by Heatmap News and Embold Research, nearly three in four registered voters (72%) told us “the environment” is extremely or very important to them personally. The environment, in fact, ranked a full 17 points higher than “climate change” in a battery of potential voter issues, despite the latter’s much more obvious existential threat. Even among the subset of people we labeled “skeptics,” for whom climate change was of minimal to no importance, a third (32%) still told us the environment matters to them greatly.

Keep reading...Show less
Green
AM Briefing

Carbon Free-for-All

On refineries, Europeanizing Canada, and Australian uranium

The J.H. Campbell power plant.
Heatmap Illustration/Getty Images

Current conditions: The Atlantic set a record on Saturday for the longest stretch of the hurricane season since the advent of satellites without a major named storm • Argentina is bracing for severe Zonda winds, a type of intense downslope gust unique to the eastern side of the Andes Mountains • While the wildfires darkening skies over Indonesia have receded, blazes are still raging across the southern shores of Sumatra, Borneo, and West Papua.


THE TOP FIVE

1. EPA plans to repeal climate rules on power plants

The United States is preparing to eliminate any cap on the amount of planet-warming pollution from burning coal or gas that power plants can spew into the atmosphere. On Sunday night, The New York Times reported that the Environmental Protection Agency planned to announce a final repeal of climate rules on the power sector at this week’s summit in Houston of energy ministers from the Group of 20 nations. The EPA already moved to remove the entire legal basis for regulating greenhouse gases at any level by gutting its endangerment finding, which my colleagues Robinson Meyer and Emily Pontecorvo explained last winter. In March, as I told you at the time, almost half of all U.S. states sued to block the administration from rescinding the finding. The EPA went on to scrap standards on climate-heating emissions for car tailpipes and loosened rules on heat-trapping chemicals used in refrigerators and air conditioners. Under the new proposal, which the Times noted would come out Monday, power plants would still face limits on mercury, arsenic, and other contaminants, “though the EPA has already loosened restrictions on how much mercury they can emit.”

Keep reading...Show less
Blue
Energy

New Englanders Will Pay Through the Nose to Stay Warm This Winter

Even the hardiest are shivering at the price of heating oil.

Heating oil and money.
Heatmap Illustration/Getty Images

As leaves begin to turn from green to autumn hues of amber, gold, and brown, New England is preparing for an expensive winter.

While most of the country heats their homes with natural gas or electricity, about 5 million households — overwhelmingly located in the Northeast — use oil. Like diesel and gasoline (both of which have set price records recently) home heating oil is distilled from crude oil, which is currently trading at prices not seen since the early months of the war between the United States, Israel, and Iran.

Keep reading...Show less
Green