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How California Kept the Lights on During Record Heat Wave

Updated: Nov 21

By Media Office Staff


SACRAMENTO California's electricity demand reached an all-time high during September’s record heat wave, but planning and conservation actions meant no outages despite the strain on the electrical grid.


California’s energy and water agencies made the grid more resilient and reliable to avoid a repeat of the 2020 outages. Several key agencies recently provided an overview of the challenges and actions taken, including a report from the California Independent System Operator (ISO) released on Nov. 2 and a presentation from the staff at the California Energy Commission’s (CEC) Oct. 12 business meeting.


During the meeting, CEC Vice Chair Siva Gunda said efforts should continue to create an electricity system that can meet the challenges as the state transitions to a clean energy future that is reliable and affordable for all.

“This is the time to double down—triple down—to make sure we address climate change…. and we need to come together to make this happen,” he said.


After the outages in 2020, Governor Gavin Newsom called on the CEC, ISO, and the California Public Utilities Commission to conduct a root-cause analysis. Key findings of that analysis led the state to take action to improve grid reliability and prepare for this year’s extreme heat emergency.


According to the report, extreme weather conditions, issues with resource adequacy and planning processes, and market practices led to the 2020 outages.

Planning differently

The analysis showed that demand forecasting needs to factor in climate change uncertainty instead of relying on historical climate data. Climate change is happening faster than anticipated, with compounding effects that raise energy demand (for air conditioning, for example) and sometimes reduce electricity supply.


The increasing number and size of wildfires, such as the Bootleg fire in 2021, can cut off power imports by damaging transmission lines. Severe drought also affects the electricity supply by decreasing hydropower. Since 2020, the state has procured unprecedented power supplies for unforeseen events, increased its effective planning reserve margin, and identified emergency contingency measures, said David Erne, deputy director for the CEC’s Energy Assessments Division.

Lessons learned: What worked in 2022

During the heat wave, a state of emergency was declared, and the new strategic reliability reserve delivered additional energy through the emergency generation and electricity imports. The state also called on 300 megawatts (MW) of power through the CEC’s Demand Side Grid Support program, launched just before the event. Electric customers signed up to provide load reduction and backup generation to the grid during extreme events in exchange for reimbursement, reducing the risk of outages. Transfers from other balancing authorities provided more reserves.


The reserves were needed for the most critical hours of the day, from 4 p.m. to 9 p.m., when solar generation wanes and electricity demand surges to cool homes and run appliances. Those net peak hours are also when California’s growing utility-scale battery storage shines—more than 4,000 MW in the ISO territory alone. They charged up when solar generation was greatest (and would otherwise have been curtailed) and worked when solar stopped feeding the grid.


Among the emergency contingency resources that kicked in were Flex Alerts calling on the public to conserve power and an emergency alert via cell phone on Sept. 6 that reduced energy consumption by thousands of MWs within 30 minutes.


Hard work and planning, but also luck

Erne said as difficult as September was, it was not a worst-case scenario because several things worked in California’s favor: the wind picked up during net peak hours, generating more electricity from turbines. The generation fleet supplying the grid experienced little downtime—no small feat for equipment running during very high temperatures. CAL FIRE kept unpredictable fires from encroaching on transmission lines. And power imports (including hydropower) were higher than normal times—even more remarkable during a West-wide heat wave.




To help California continue strengthening its grid efforts, Governor Newsom provided $3.4 billion for summer reliability in the 2022-2023 state budget. This included $2.4 billion for the strategic reliability reserve to procure backup power for use when the grid is strained; $295 million for demand-side grid support, enabling major users to be compensated to reduce use during emergencies; and $700 million to fund distributed backup assets.


Together, these investments will help California meet its ambitious climate goals, which include 90 percent clean electricity by 2035 and 95 percent by 2040. All while keeping the lights on.

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