Driven by solar, California’s net demand hit zero on Sunday


On Sunday, California’s CAISO region reported that its electricity “net demand” bounced near zero for chunks of the afternoon. The power grid operator defines net load as total electricity demand minus wind and solar power.

Starting at 12:20 PST, CAISO first reported net demand at negative 63 MW. At the moment, total grid demand was 13.8 GW. It was offset by 12.4 GW of utility managed solar, and 1.5 GW of wind.

While CAISO’s demand was noted as being nearly 14 GW, total true demand was above 20 GW at the moment when taking into account the greater than 10 GW of behind-the-meter solar power deployed in the power grid region.

Combined, solar was meeting greater than 90% of California’s electricity needs at the moment.

At the same time that CAISO first noted a net demand below zero, at 12:20 p.m., the overall supply picture was much more complex. First, there was greater than 4.7 GW of natural gas running, as well as electricity exports of over 4.9 GW.

According to Grid Status’ Max Kanter, Sunday set a record for the highest electricity export ever from CAISO.

In addition to the gas and 4 MW of coal burning somewhere in the state, batteries and multiple other clean sources were doing their job. Just over 2 GW of batteries were being charged, along with just over 4 GW of combined nuclear and hydroelectric power were pumping.

In fact, starting at 8:10 a.m. and going until 5:50 p.m. – nine hours and forty minutes – CAISO’s total electricity demand could be covered by its clean resources of nuclear, hydro, wind and solar.

CAISO’s curtailment report from Sunday shows that there was some solar power being shut down during the day. The report noted that during the noon hour, when the state officially broke below zero on net load by 0.063 GW, solar curtailment capacity peaked at just over 1.7 GW, with 1.54 GWh of electricity not being generated. On April 18, 2023 solar peaked at greater than 14 GW.

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