News

CAL-ISO issues Flex Alert for Thursday

Extreme heat forecast; consumer help will be key to preventing outages

FOLSOM, Calif. – The California Independent System Operator (ISO), with extreme
heat forecast for much of California and the Southwest, has issued a statewide Flex
Alert to encourage electricity conservation tomorrow from 5 p.m. to 10 p.m. to reduce stress on the grid and avoid power outages.

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.

“The public’s help is essential when extreme weather or other factors beyond our
control put undue stress on the electric grid. We have seen the huge impact that occurs when consumers pitch in and limit their energy use. Their cooperation can really make a difference.”

Elliot Mainzer, president and chief
executive officer of the ISO

While Flex Alerts are normally 4 p.m. to 9 p.m., the hours of conservation for this event are 5 p.m. to 10 p.m. due to operational needs. The statewide call for conservation is critical because when temperatures hit triple digits across a wide geographic area, no state has enough energy available to meet all the heightened demand, primarily due to air conditioning use.

For the next several days, much of California and the Southwest are expected to see
triple-digit heat with above normal temperatures spread more broadly across much of
the Western United States. And like California, other Western states – including Arizona and New Mexico – are experiencing similar stressful grid conditions due to the extreme heat.

Under such conditions, evening is the most difficult time of day for grid operations,
especially in persistent hot weather when evening temperatures stay warm, because
demand for electricity remains high as solar energy diminishes.

By collectively taking a few simple actions, electricity use can be reduced enough to
keep power on for everyone. Last August and September, for instance, Californians
heeded multiple Flex Alerts and Gov. Gavin Newsom’s call for a concerted response to
emergency condition and reduced electricity use by 1,000 to 3,000 megawatts. That is enough electricity to power up to 3 million homes, and the conservation likely prevented subsequent and more severe rotating outages last August and September.
If demand still outstrips supply after Flex Alerts and other measures are taken, the ISO could again order utilities to begin rotating power outages. That would extend available power supplies and guard against longer and more extensive disruptions while protecting high-voltage transmission lines from damage.

As California’s ability to store solar and wind energy with batteries or other technology continues to increase, the crucial evening hours will be less challenging. But for now, concerted action to conserve is our most effective way of keeping the grid working for everyone.

Conservation Tips

Before a Flex Alert is in effect, consumers can take specific steps to manage their
electricity usage to maintain comfort during days that conservation is needed.
Specifically, consumers can:

  • 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


From 5 p.m. to 10 p.m. today, when the statewide Flex Alert is in effect, consumers
can help by:

  • Setting your thermostat to 78 degrees or higher, if health permits
  • Avoiding the use of major appliances
  • Turning off all unnecessary lights
  • Using fans for cooling
  • Unplugging unused items