As astronomy enthusiasts headed for the path of totality on Aug. 21 to witness the first coast-to-coast total eclipse in the U.S. for nearly a century, grid operators from California to the Carolinas braced for a dip in solar generation.
California, where solar makes up almost 14% of installed capacity, was one of the states where the impact of the eclipse was greatest.
Solar capacity, including solar thermal generation, fell to about 3.6 GW at 11 a.m. Pacific Time as the moon’s shadow moved over the state, according to data provided by California ISO. On the following day, which was more typical, solar generation hit about 9.5 GW at the same time.
The roughly 6 GW drop was made up for partly with additional conventional and hydro generation, although there was also a spike in power imported to California, according to the data.
In PJM Interconnection, most of which lies outside of the path of totality of the eclipse, the blip was less noticeable.
Solar capacity across the region plunged from a peak of 578 MW at 1 p.m. Eastern Time to 184 MW at 2 p.m., but this was a drop in the ocean compared with the 132 GW of total capacity that was online at the time.
In North Carolina, meanwhile, Duke Energy lost about 1.7 GW of solar generation, but “avoided any grid problems,” according to a tweet from Randy Wheeless, a communications manager at the Charlotte-based utility.
Grid operators spent about a year planning for the eclipse and their hard work seems to have paid off.
The experience may prove to be educational for the next solar eclipse, which is due to affect the U.S. in 2024, which will affect different parts of the country. The path of totality will cut through the middle of Texas and stretch northeast to New England.