California, live
The duck curve
The most famous shape in energy, drawn live from California's own grid. Net load is demand minus wind and solar. Watch it sink into the midday belly as solar peaks, then ramp through the evening as the sun sets and demand holds. The gap between the two lines is the renewable output making the duck.
Net load todaydemand minus wind and solar
What is the duck curve?
The duck curve is the shape California's net load traces over a day. Net load is total demand minus wind and solar. As solar floods the grid at midday, net load sinks into a belly; as the sun sets and demand holds, the grid ramps steeply into the evening. Plotted, the day looks like a duck. CAISO named it in 2013, and the belly has deepened every year as more solar comes online.
Why does the evening ramp matter?
The neck of the duck, roughly 4 to 9 PM, is the hardest part of the grid's day. Solar rolls off just as people come home and demand climbs, so dispatchable supply has to ramp tens of gigawatts in a few hours. Batteries charged on cheap midday solar now discharge into that ramp, and gas fills the rest. When the ramp is steep and reserves run thin, CAISO calls a Flex Alert.
Where does this come from?
CAISO's public feeds: five-minute system load and the five-minute fuel mix, the same data behind the live dashboard. Net load is computed as load minus the wind and solar lines. Real data only, the day as found, no projected curve.