Though a solar eclipse will cause skies to darken on August 21, the federal Energy Information Administration does not anticipate the eclipse will cause reliability issues for power systems that have incorporated solar.

The optimistic projection is based on the fact that relatively little solar capacity is located in the path that will have the sun totally obscured by the moon.  A total of 1,900 utility-scale solar power plants in all will be affected and only 17 plants, mostly in Oregon, are in the path of total blockage.  Diminished capacity for a few hours is expected, especially in California and North Carolina.

Solar makes up 40 percent of the total capacity in California. Though the state is not in the path of totality, the California Independent System Operator indicated solar capacity will fall by 4.2 GW during the eclipse. North Carolina, which has 2.8 GW of solar or 13 percent of the national total, will see its solar energy output drop from 2.5 GW to 0.2 GW.

To maintain grid reliability, solar facilities will have to use a complex combination of other sources of power generation. Natural gas plants and hydro plants will likely be the go-to alternatives to fill the demand gap.