What Comes of Solar Power When the Sun’s Eclipsed: QuickTake Q&A

The last time a total eclipse cast a shadow across the entirety of the U.S., from West Coast to East, was 99 years ago. Back then, the modern power grid was just getting started, and harnessing the sun’s energy on a widespread scale was little more than a notion in the minds of scientists. On Aug. 21, when the moon will completely obscure the sun across a swath of the U.S., the rare daytime darkness will affect a real -- though still small -- segment of the energy supply.

Enough to notice. It will reduce the sunlight that reaches 1,900 solar-power plants in the U.S., according to the U.S. Energy Information Administration. More than 12,000 megawatts of solar generation may be forced off line during the roughly four-hour event, equivalent to the power of about 12 nuclear reactors. Though few power plants are within the narrow band of land that will see a total eclipse, some reduction in sunlight will be experienced everywhere in the U.S.