A brutal heatwave across much of California stressed the state’s power grid and left millions of people on edge worrying about whether or not their homes could have their power knocked off.

According to the California Independent System Operator, the power grid set an all-time record for energy delivered on Tuesday, Sept. 6, but rotating outages weren’t needed.

So how did that happen?

Representatives for Cal ISO say a big part was the messaging.

On the morning of Sept. 6, the ISO issued an Energy Emergency Alert 2, which signals to utilities to bid more energy into the market and allows for the ISO to tap into its emergency response programs.

Consumers were urged to cut back on their energy usage for another consecutive day, which had been successful earlier in the week, but demand continued to outpace what the state’s power grid could handle.

As temperatures continued to skyrocket into triple digits and Californians utilized their air conditioners to cool down, the grid became stressed under the record-breaking demand.

Around 5:20 p.m., Cal ISO issued an Energy Emergency Alert 3, which signals to utilities that rotating power outages might be called for to reduce demand on the system and prevent larger scale “cascading blackouts” that can spread to other areas throughout the western United States.

“Our grid peaked at 52,061 megawatts, a level we have not seen before in California. Of note, it was also the highest recorded load for the broader Western interconnection,” said Cal ISO President and CEO Elliot Mainzer in a recorded briefing the following day.

Over the next 30 minutes, conditions continued to deteriorate, Mainzer said, which led to something that doesn’t happen very often.

“Gov. Newsom triggered the statewide wireless emergency alert to Californians across the state, calling for immediate reductions in electricity service to avoid the need for rotating outages,” Mainzer said.

“Emergency Alert: CAOES Conserve energy to protect public health and safety. Turn off nonessential power now,” the alert read.

The impact of that wireless alert, which went directly to the cell phones of millions of Californians, was immediate.

Less than 30 minutes after the alert went out, the grid saw a load reduction between 2,000 and 2,500 megawatts, which helped restore operating reserves and kept the need for rolling blackouts at bay.

Mainzer credited Californians heeding the warning of Cal ISO and state officials and working together to avoid dangerous power outages.

“When we get a lot of people to change their behavior in just a few relatively small ways we can accomplish big things,” Mainzer said.

Cal ISO says its teams are validating data to fully analyze the complete impact of the local cooperation.

But it wasn’t just togetherness that helped avert blackouts. California has made some meaningful changes to the grid in the previous years to avoid shutoffs.

Since July 2020, California has added massive battery systems to the grid to help with peak load. On Sept. 5, the day before the statewide notification was sent, the state’s grid received more than 3,300 megawatts of power from its battery systems.

Mainzer called those batteries “unquestionably helpful” in avoiding shutoffs.

Those batteries, in addition to emergency resources made available by issuing emergency alerts, and in conjunction with conservation efforts, kept the lights on in California — figuratively speaking.

For more information about Flex Alerts and the California Independent Operator, click here.