Chart: California is wasting more and more clean energy

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California is throwing away a lot of solar power.

The state curtailed 3,400 gigawatt-hours of utility-scale renewable electricity last year, 93% of which was produced by solar panels, per a U.S. Energy Information Administration analysis of data from California’s grid operator.

When the sun shines bright and the breeze blows hard, solar panels and wind turbines often produce more power than the grid needs or can handle. In those moments, the grid operator will order power plant owners to reduce their output. That’s called curtailment, and it’s common in places like California that have lots of renewables.

It’s no surprise that California is having to curtail power as it adds more solar to the grid — but curtailments are rising faster in the state than renewable generation capacity is growing. Last year, curtailments jumped by 29% compared with 2023, while California added only about 12% more utility-scale solar capacity.

Curtailments are at their highest in California during the spring, when the sun is strong enough to generate a lot of solar power but mild weather keeps air-conditioning use, and thus electricity demand, in check.

With power demand rising around the country thanks in large part to the rapid rollout of AI data centers, and with California behind on climate goals, it’s important for the state to try and reduce curtailments and use more of the clean power it’s already capable of generating.

There are a few ways to do that. California can continue to push buildings, vehicles, and industrial operations to electrify, creating more demand to soak up what is now surplus solar. It can support the construction of interstate transmission lines that would allow it to export more power to states with less solar generation.

The state can also build lots and lots of batteries to store extra solar produced during the day for use in the evening. In fact, it’s already doing that. It has installed more utility-scale storage than any other state, and the sector has grown rapidly in recent years: California had a total of 13.2 GW of utility-scale storage online as of last month, far more than the nearly 8 GW it had at the end of 2023.

In order to stop wasting clean electricity, California will need to sustain that battery boom in the face of significant federal policy headwinds — and place some bets on other, more elusive solutions like transmission and long-duration energy storage.

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