Duck Curve
Prerequisites
California's grid operator plotted net load (total demand minus solar generation) across the day and got a chart shaped like a duck. That duck is now the most important diagram in grid planning.
The duck curve is a net-load profile showing how midday solar generation suppresses the residual demand that dispatchable generators must serve, creating a midday belly and a steep evening ramp as solar fades and demand peaks. The steeper the ramp, the more fast-responding capacity (gas peakers, batteries, demand response) the grid needs on standby. As solar penetration grows, the belly deepens and the ramp steepens.
California's duck, 2012 to 2024. In 2012, CAISO's minimum net load on a spring day was about 15 GW. By 2024, that minimum had dropped below 5 GW on some days, with the evening ramp requiring 10-15 GW of generation to come online within three hours.
What happens when the belly drops to zero or goes negative?
Curtailment. When net load is negative, solar produces more than the grid can absorb. Operators curtail (shut off) solar panels that are producing electricity no one can use. CAISO curtailed roughly 2.4 million MWh of solar and wind in 2022, energy that was available for free but had no buyer. The duck curve does not mean solar is failing; it means the grid's flexibility infrastructure has not kept pace with solar deployment. Storage, demand shifting, and regional market integration are the solutions that flatten the ramp.
The "belly" of the duck curve represents:
The belly forms because solar output peaks at midday, displacing dispatchable generation. The deeper the belly, the steeper the evening ramp when solar fades.
The answer is BLesson complete
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