The duck curve is the shape of net electricity demand on a grid with a lot of solar: a midday trough when solar covers most load, then a steep evening ramp as the sun sets and demand rises. The name comes from the silhouette the daily chart makes, belly at noon and neck at dusk.
How California flattened it
- Grid batteries charge in the trough, when wholesale prices crater around noon, and discharge on the neck, between roughly 5 and 9 p.m. In 2024 they supplied about 8.6 percent of all energy on the CAISO system in those evening hours.
- The fleet went from under 100 megawatts in August 2020 to more than 17,000 megawatts by September 2026.
Why it matters for parking
Daytime garages fill during the trough and empty before the neck; residential and multifamily garages do the reverse. Which side of the duck curve a facility sits on decides whether its EV charging helps the grid or lands on the hour the batteries exist to cover. Source: California ISO.