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What is a Flex Alert?

A Flex Alert is a call for consumers to voluntarily conserve electricity when there is a predicted shortage of energy supply, especially if the grid operator needs to dip into reserves to cover demand. When consumers reduce electricity use at critical times, it can prevent more dire emergency measures, including possible power outages.

Who Issues A Flex Alert?
A Flex Alert is issued by the California Independent System Operator (ISO), a nonprofit, public benefit corporation that manages the high-voltage electric grid for 80 percent of California. Click here to learn more about the California ISO.

What Can Trigger A Flex Alert?

A Flex Alert is typically issued in the summer when extremely hot weather pushes up electricity demand. This usually happens in the evening hours when solar generation is going offline and consumers are returning home and switching on air conditioners, lights, and appliances.

Other contributing factors include:

  • Unplanned power plant outages

  • Fires that lead to transmission line losses

  • Humid, hot weather and heat storms

When Is A Flex Alert Issued?

Flex Alerts are most effective when issued a day in advance of the predicted supply gap, so consumers can better prepare for the event. But grid emergencies can also happen suddenly, so the ISO can issue a Flex Alert will little or no advance notice. When possible, Flex Alerts are targeted to local areas where the system is stressed.

How Are Consumers Notified?

Flex Alerts are distributed through the ISO Today mobile app, and promoted on the ISO website at, on Twitter and Facebook. Consumers can also subscribe to receive Flex Alert notifications either by email or cell phone text. The ISO also notifies media outlets throughout the state when a Flex Alert is issued.

When the California ISO calls a Flex Alert, residents are asked to take three simple actions:


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