Impact of solar eclipse on power grid shaped by solar

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On Monday, August 21, a rare total solar eclipse will cast a shadow across the U.S. – from the West Coast to the East Coast – for the first time in nearly 100 years. Almost a century ago, the modern power grid system was just getting its roots set in major cities. Now with solar power representing one percent of the U.S. energy generation mix and four percent of installed power capacity, this daytime darkness will have an effect on our power – but by how much?

According to the Energy Information Administration (EIA), the solar eclipse will obscure the sunlight at nearly 1,900 utility-scale solar photovoltaic (PV) power plants in the U.S.

While the direct shadow will last a mere three minutes, the entire event is expected to last three hours. Only a relatively small portion of solar PV capacity will be completely shadowed by the moon in the “zone of totality,” but some reduction of sunlight will be experienced everywhere in the U.S. 17 utility-scale solar PV generators, mostly in eastern Oregon, are in the zone of totality, and roughly 4.0 gigawatts (GW) of capacity will be at least 90 percent obscured, says the EIA.

This means that during the eclipse places that depend on solar for power should increase generation from other sources to make up for the lost solar capacity.

The California Independent System Operator (CAISO) is encouraging companies and residents to pledge to “do one small thing to reduce energy usage” during the eclipse. California, with 8.8 GW of utility-scale PV, making up 40 percent of the U.S. total capacity, is gearing up for the eclipse by replacing solar generation with electricity from natural gas and hydropower. CAISO estimates that while the state is shadowed between 9:02 a.m. and 11:54 a.m., 4.2 GW of solar capacity will be offline.

The North American Reliability Council Corp. says any service disruptions will be highly unlikely since transmission operators have had months to prepare for the eclipse.

Beware that wholesale electricity prices might spike on Monday morning while solar generation is falling. Bloomberg New Energy Finance says that California expects to see solar generation fall off at a rate of 70 MW per minute over an 82-minute period, potentially creating bottlenecks along the grid. Prices may also dip down as folks are outside watching the eclipse and decreasing the demand for air conditioning.

My recommendation: On Monday, turn off your lights, grab a pair of eclipse glasses for safety, and step outside to enjoy a show that many of us will not see again in our lifetimes.

About the author:

Brooke Ousterhout is a Senior Energy Analyst and Project Coordinator with JLL Clean Energy. Brooke is a subject matter expert on energy and market trends, and provides superior data analytics. She also works with JLL’s Portfolio Energy Managers to develop strategic energy and sustainability programs and identify energy-saving opportunities for clients. Brooke maintains her LEED Green Associate and is an active member of Chicago Advanced Energy, American Planning Association and the USGBC.

2 thoughts on “Impact of solar eclipse on power grid shaped by solar

    1. Brooke

      Hi Frank – Thanks for the question! As we predicted, so many folks were outside observing the eclipse that electric demand fell creating a weird u-shaped dip over a two-hour period during the typical morning ramp-up period. ConEd saw demand fall by 5,000 MW in the NE. Spot prices also dropped as solar came back online when the sun reappeared which will be important to remember for the next eclipse in 2024!


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