The eclipse set to darken skies next month threatens to sideline solar farms and rooftop panels in a wide swath of the U.S., wiping out enough power generation to supply about 7 million homes.
The moon will completely obscure the sun this rare event, will cast a shadow along a 70-mile-wide (113-kilometer) corridor stretching from Oregon to South Carolina on Aug. 21. Based on a Bloomberg calculation of grid forecasts, more than 9,000 megawatts of power generated by massive solar farms and rooftop panels may go down. That's the equivalent of about nine nuclear reactors.
The impact is a testament to the ninefold increase in solar installed in the U.S. since 2012 and highlights the risks associated with relying on an intermittent resource such as the sun for power.
Operator of the nation's largest power grid PJM Interconnection LLC, covering a large part of the eastern U.S., estimated the eclipse could take out as much as 2,500 megawatts of solar about 1:30 p.m. to 3:40 p.m. generation on its system on Thursday. North Carolina and New Jersey may bear the brunt because so many panels are installed in those states.
The duration of the eclipse (12:05 p.m. to 4:09 p.m. New York time) is too short to meaningfully boost demand for fossil fuels. In wholesale power prices it might trigger spikes, especially since demand tends to surge in the summer as people blast their air conditioners. The last time the contiguous U.S. saw a total eclipse was in 1979, according to NASA.
"If it is sunny and all of the sudden the eclipse comes through, there may be a pricing spike in real-time" power trading, said Tom DiCapua, managing director at Con Edison Energy in Valhalla, New York.
The biggest impact to solar generation might be seen by California, as it meets about 40 percent of the state's demand on some days. About 70 percent the eclipse stands to dim solar radiation, said by Dave Quinn, a power market analyst at energy data provider Genscape Inc.
As per the grid operator of California, generation from large solar farms may plunge by 70 megawatts a minute over an 82-minute period and then begin surging 90 megawatts a minute as the sun re-emerges.
Texas's power grid operator expects the eclipse to affect about 600 megawatts of solar generation over an hour to 90 minutes. From the Midwest into Louisiana the operator of a grid that stretches estimated a potential impact of as much as 125 megawatts.