Flex Alert in effect today from 5 p.m. to 10 p.m.

June 17, 2021


Voluntary conservation encouraged to keep grid stable during extreme heat

FOLSOM, Calif. – The California Independent System Operator’s (ISO) first Flex Alert of the year takes effect this afternoon, with consumers encouraged to voluntarily conserve electricity from 5 p.m. to 10 p.m. to help maintain grid stability while California and much of the Southwest experience triple-digit temperatures the next several days.

Once the Flex Alert conservation period begins, consumers are asked to:

  • Set thermostats to 78 degrees or higher, if health permits
  • Avoid using major appliances
  • Turn off all unnecessary lights

Consumers are also encouraged to use fans for cooling and unplug unused electrical items. Additional tips can be found at the website, Flex Alert.org, where people can also sign up to receive Flex Alert notifications.

To be as comfortable as possible during the Flex Alert hours, consumers are also encouraged to manage electricity use by taking these steps before 5 p.m. today:

  • Pre-cool your home by lowering the thermostat
  • Use major appliances, like your dishwasher, and clothes washer and dryer
  • Close window coverings to keep your home or apartment cool
  • Charge electronic devices
  • Charge electric vehicles

In a conference call with reporters yesterday, Elliot Mainzer, president and chief executive officer of the ISO, said the Flex Alert was being called “in a preponderance of caution” because demand and supply forecasts for today show a relatively modest shortfall of about 300 megawatts (MW) of electricity available to the grid. Grid operators believe voluntary conservation should close the gap, making the likelihood of rotating outages remote.

“We certainly know from experience, including last August and September, that Californians can make a huge difference in helping maintain overall grid stability by taking these very straight-forward and pragmatic steps to help conserve,” Mainzer told reporters.

Today is expected to be the hottest day of the week in Northern California, with high temperatures forecasted to reach between 100 and 110 degrees. Heat warnings continue to be in effect for much of Southern California, and states across much of the Southwest are experiencing similar temperatures and stress on their electric grids.

When past Flex Alerts have been called, consumers have answered the call and cut back their electricity use. Those actions have helped California avoid or limit power outages that can, if conditions persist or worsen, become necessary when demand for electricity outstrips capacity.

While typically set from 4 p.m. to 9 p.m., the precise time for the Flex Alerts varies depending on hourly projections of supply and demand. Grid operators said the 5 p.m. to 10 p.m. period will be the most challenging time for the electric system today based on those projections.

The ISO continues to closely monitor weather and grid conditions and will report later today whether a Flex Alert is also needed on Friday.

For information on Flex Alerts, to get more electricity conservation tips, and to sign up for conservation alerts, visit the ISO's Flex Alert website. Visit the ISO's News page for more information on the heat wave's impacts on grid operations, and to learn more about alerts, warnings and emergency notices.

For updates on grid operations, follow us on Twitter at @California_ISO or @FlexAlert, or monitor system conditions in real time at ISO's Today's Outlook.

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A Flex Alert is issued by the ISO when the electricity grid is under stress because of generation or transmission outages, or from persistent hot temperatures. Glossary of terms and acronyms

Click here to learn more about System Alerts, Warnings and Emergencies. Follow grid conditions in real time at ISO’s Today’s Outlook, or download the free ISO Today mobile app.

This advisory is based on the best data available at the time of its release. Grid conditions can change rapidly and are
subject to change without warning. This forecast is accepted by the recipient on the condition that errors, omissions
and/or changes to the contents shall not be made the basis for any claim, demand or cause of action against the California ISO.