When the sun disappears, your electricity won’t

Industry experts agree the grid is ready for the full solar eclipse.

Electric grid operators predict the full solar eclipse on August 21, 2017 will cause no reliability issues. CREDIT: Rodrigo Pena/AP Images for The Pew Charitable Trusts
Electric grid operators predict the full solar eclipse on August 21, 2017 will cause no reliability issues. CREDIT: Rodrigo Pena/AP Images for The Pew Charitable Trusts

The last time the United States witnessed a full solar eclipse was 1979. America’s electricity picture has changed dramatically since then — states now rely more heavily on solar energy, and that trend is prompting questions and concerns regarding how the nation’s electric grid will handle Monday’s full solar eclipse.

Industry experts, however, agree there’s nothing to fear. They’ve concluded there’s little chance the eclipse will cause any reliability problems in regions with large amounts of solar capacity along its path.

The North American Electric Reliability Corporation, the electric grid monitor for the continent, conducted an in-depth analysis and concluded the eclipse will have no impact on the reliability of the nation’s power system. Grid operators and electric utilities that rely on solar energy for a considerable portion of their generating capacity are reassuring customers they are prepared for the eclipse.

The eclipse will at least partially obscure the sunlight from about 1,900 utility-scale solar photovoltaic power facilities. The path of the total eclipse will span the United States, starting in Oregon and moving eastward to South Carolina over the course of approximately 90 minutes.


The pace of solar energy installations has increased significantly over the past decade and has continued into 2017. After installing almost 2,100 megawatts of solar capacity during the first three months of this year, the United States now has nearly 45,000 megawatts of solar capacity.

“The fact that we’re even talking about solar in the context of this eclipse is a huge testament to the clean energy progress that we’re seeing in states all along the path of the eclipse,” Rosalind Jackson, a director at Vote Solar, a national solar advocacy group, told ThinkProgress. “Once little more than a rounding error in our nation’s energy mix, the U.S. now has enough solar capacity installed to power 8.7 million American homes and employ more than 260,000 solar workers.”

The eclipse will have a predictable and manageable impact on the nation’s solar production. Regional grid operators have had plenty of time to plan and are confident that they will be able to keep the lights as solar productions dips, Jackson said.

Nuclear, coal, and natural gas generating facilities often are idled for weeks or months as they undergo regular maintenance or refueling. Solar energy facilities rarely face outages of similar lengths.

“Take a look at California where more than 6,400 megawatts of natural gas and nuclear power — enough to power 7 million homes — were unavailable for service during a June heat wave that cause generator malfunctions,” Jackson said. “Meanwhile, solar was able to tap that same summer sunshine to produce reliable power.”


The next full solar eclipse is not scheduled to affect a portion of the United States for another seven years. Nevertheless, when that solar eclipse occurs in 2024, the amount of solar power connected to the grid is expected to increase significantly, so changes will need to be made between now and then to ensure the grid can handle an even greater percentage of generating capacity going off-line for an hour or longer.

CREDIT: Energy Information Administration
CREDIT: Energy Information Administration

Solar’s increasing competitiveness against other technologies has allowed it to quickly increase its share of total U.S. electrical generation, from just 0.1% in 2010 to 1.4% today.  By 2020, solar is expected to surpass 3% of total generation and is expected to hit 5% by 2022, according to the Solar Energy Industries Association.

Actual disruptions of the electric power system, however, typically do not occur when the disturbance, like Monday’s solar eclipse, is predicted to the precise day and hour, Mike Jacobs, senior energy analyst in the climate and energy program at the Union of Concerned Scientists, wrote in a blog post on the eclipse. They are most often caused by trouble with electric distribution and transmission lines, he said.

“We can resist the fear that ‘the sun won’t shine’ used to attack renewable energy,” Jacobs said. “The power supply is always prepared for swings of more sudden losses than this — those that come from man-made, not natural, plant failures.”

Opponents of renewable energy have found a champion at the Department of Energy where Secretary Rick Perry ordered his staff to conduct a study of the nation’s electric grid to find out if renewable energy sources are harming electric power reliability. DOE has yet to release the study — it’s almost two months overdue — but other researchers have noted the presence of high amounts of renewable energy in Europe has not made the grid less reliable in those nations.

In 2015, the European power grid, after months of preparation, easily handled the drop-off of solar power generation during a total solar eclipse and dealt with the photovoltaic panels coming back online with equal success. In preparation for Monday’s eclipse, grid operators in California and utilities in the Southeast have studied how Europe successfully handled the 2015 eclipse and have developed similar plans to ensure grid reliability during this rare event.

Utilities and grid operators in these regions have plotted out comprehensive demand management strategies and have arranged substitute energy sources to dispatch as needed during the time where the shadow of the moon is directly over an area, according to the American Council on Renewable Energy, a renewable energy industry group.


Based on the amount of sunlight obscured for each of the state’s generators, California’s grid operator estimates that the state will experience a reduction in solar generating capacity of almost 4.2 gigawatts during the eclipse, which is estimated to partially darken the state from 9:02 a.m. to 11:54 a.m. local time, according to the U.S. Energy Information Administration. An estimated 6,000 megawatts of grid-connected storage is expected to support California’s grid through ramping and other support services. (Ramping is an energy storage service that allows generators to quickly increase or decrease electricity production over a short period of time.)

In North Carolina, Duke Energy, one of the largest utilities in the state, estimates that solar energy output across its system will drop from about 2.5 gigawatts to 0.2 gigawatts at the height of the eclipse. The utility said it does not expect any reliability issues during the eclipse.

“Solar is an important part of our nation’s electricity mix and will continue to be so in the hours leading up to the eclipse and immediately following. Our nation has been preparing for this for more than a year and grid operators are confident they are ready to maintain electricity during the three hours of impact,” Dan Whitten, vice president of communications for the Solar Energy Industries Association, said in a statement.