Solar power curtailment rises in California

Curtailment – the intentional reduction of power production – continues to rise for both solar and wind power in California.

Grid Balancing Challenges: Solar Curtailment Rises in California

Grid operators play a critical role in maintaining stability by balancing electricity supply with demand. When generation significantly outpaces consumption, operators must reduce output—a practice known as curtailment. In California, solar curtailment has surged in recent years, hitting record levels in 2024 according to the U.S. Energy Information Administration (EIA).

The Solar Curtailment Dominance

Within the California Independent System Operator (CAISO) network—serving most of the state—solar accounts for 93% of all curtailed energy. In 2024 alone, CAISO reduced 3.4 million MWh of utility-scale wind and solar production, marking a 29% increase from 2023.

Drivers of Curtailment

While market pricing frequently dictates these reductions, grid operators may also mandate shutdowns during congestion or oversupply events. Notably, CAISO sometimes curtails solar to preserve natural gas generation capacity, which must remain available per North American Electric Reliability Corporation (NERC) standards to ensure evening ramp-up capability.

Mitigation Strategies

CAISO is implementing multiple approaches to minimize waste:

Expanding energy exchanges with neighboring grids to offload surplus renewable power
Integrating battery storage into energy and ancillary service markets
Prioritizing curtailment reduction in transmission infrastructure planning
Innovative Utilization

Industry players are exploring alternative applications for excess renewable energy, including green hydrogen production. Some hydrogen output will be stored and blended with natural gas to bolster supply during peak summer demand.

The Storage Solution

Battery systems with 4-8 hour dispatch durations are proving particularly effective. These installations absorb surplus midday solar energy for later use during evening demand spikes—when solar generation wanes just as consumption rises with residential air conditioning and appliance use.

Capacity Growth Trends

Energy storage deployments are accelerating to address this mismatch, with CAISO’s battery capacity jumping 45% year-over-year to 11.6 GW in 2024. Meanwhile, California’s renewable capacity has tripled from 9.7 GW (2014) to 28.2 GW (2024), underscoring the growing need for flexible grid solutions.

As renewable penetration continues climbing, grid operators face intensifying pressure to develop new methods for synchronizing clean energy production with consumption patterns.