FOLSOM, Calif. – The California Independent System Operator (ISO) is alerting Californians to be ready for potential rotating power outages on Tuesday evening, as the hottest weather of this historic heat wave is forecast to push electricity demand to an all-time high.

If outages are initiated, consumers can expect to receive notifications from power providers on areas affected and time duration.

The ISO declared an Energy Emergency Alert (EEA) 2 for 4 p.m. to 9 p.m. tonight, which signals to participants to bid more energy into the market, and allows the ISO to tap into emergency demand response programs that provide financial incentives for reducing energy use. The ISO is expected to declare an EEA 3 around 5:30 p.m., one step away from ordering rotating power outages.

On Monday evening, an emergency declaration pulled additional resources onto the system at a time when the grid was dipping into reserves and there was risk of further emergency action, including power outages. Peak demand was 49,020 megawatts (MW), but consumer conservation, imports, and emergency resources fended off outages.

Consumer and commercial demand response, including Flex Alerts, has been helping to extend sparse supplies at critical hours so far this week, giving operators extra cushion in supplies. Yesterday, demand response conservation was scheduled to save about 2,000 MW of power when it was most needed. Emergency assistance added another approximate 800 MW of power on the system. This amount of energy was able to help tide the system over during the evening.

But tonight, electricity demand is currently forecast at more than 52,000 megawatts (MW), a new historic all-time high for the grid. As the state faces the hottest day in this prolonged, record-breaking heat wave, grid conditions are expected to worsen.

If needed, ISO could order utilities to begin rotating power outages to maintain stability of the electric grid. If that occurs, consumers should expect communications – either phone, text or email – from their utilities notifying them of outage areas and likely durations.

Rotating power outages, or small-scale, contained, controlled interruptions in power, can help maintain reliability and avoid cascading blackouts. When the ISO determines that supplies are not sufficient to meet demand, it can issue an EEA 3, and then if reserves are exhausted, it would order utilities to begin outages to bring demand back in line with available supplies.

Outages are a significant inconvenience to those affected, but it’s preferable to manage emergencies in a controlled manner rather than let it cause a wider spread, longer lasting disruption.

Power interruptions are kept as brief as possible and utilities rotate them through their customer base so that no one area has prolonged outages. Utilities make the determination of how best to spread and rotate the outages across their customer base, with the goal of limiting their duration as much as possible.

For two days in August 2020, planned outages affecting about 800,000 homes and businesses lasted anywhere from 15 minutes to about 2 ½ hours, marking the first time outages were ordered in California due to insufficient supplies in nearly 20 years.

Planned outages are implemented when the all the other emergency tools on hand for the ISO, utilities and state agencieds have been used and supplies are still insufficient to cover demand. Consumers are encouraged to check their utility websites for outage maps and preparation tips:

Rotating power outages are called to protect the reliability of the California ISO’s grid and in neighboring balancing authorities. Reducing demand to match supply maintains grid reliability and ensures the system doesn’t collapse into uncontrolled, unplanned power failures, possibly across the West.

The ISO will work closely with California utilities and neighboring power systems to restore the power grid to full capacity as quickly as possible.

For more information, see our Rotating Power Outages fact sheet.

Consumers and businesses can protect grid reliability by doing their part to lower electricity use during tonight’s Flex Alert from 4 p.m. to 9 p.m. Consumers are encouraged to pre-cool their homes today by setting thermostats as low as 72 degrees, and cooking, doing laundry, and running dishwashers earlier in the day.

From 4 p.m. to 9 p.m., consumers are urged to set thermostats to 78 degrees, avoid use of major appliances, and turn out unnecessary lights. Reducing demand on the system at the critical time can help prevent possible power outages.

To learn more about EEA designations, view the Emergency Notifications fact sheet. For the most up-to-date information on emergencies, follow grid conditions in real time on ISO’s Today’s Outlook, download the free ISO Today mobile app, and follow us on Twitter at @California_ISO.