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Calif. grid operator initiates rotating power outages with extreme heat, high power demand

August 17, 2020

by Paul Ciampoli
APPA News Director
August 17, 2020

Against the backdrop of scorching temperatures and a spike in demand for power, California’s grid operator on Aug. 14 and Aug. 15 initiated rotating power outages throughout the state.

The California Independent System Operator (CAISO) on Aug. 14 declared a Stage 3 electrical emergency due to high heat and increased electricity demand. The emergency initiated rotating outages throughout the state.

A Stage 3 emergency is declared when demand outpaces available supply. “Rotating power interruptions have been initiated to maintain stability of the electric grid,” CAISO said.

The Stage 3 emergency declaration was called after extreme heat drove up electricity demand across California, causing the ISO to dip into its operating reserves for supply to cover demand.

The grid operator went into Stage 3 Emergency at 6:36 p.m. PDT. By 7:51 p.m., the grid had stabilized, and utilities began restoring 1,000 megawatts of electricity that had been taken out of service.

CAISO terminated its Stage 3 Emergency declaration at 8:54 p.m. on Aug. 14.

“The power crisis was caused in part by coronavirus restrictions, which have closed movie theaters, malls and other locations where people would typically gather to beat the heat. Concerns about outbreaks have kept many inside their homes with the air conditioning on,” the Los Angeles Times reported on Aug. 15.

Investor-owned Pacific Gas & Electric (PG&E) on Aug. 16 said that the COVID-19 pandemic “has made the heat-outage forecast more uncertain due to shifts in electric loads because more people are staying home all day.”

Investor-owned utilities

PG&E on Aug. 14 reported that it was directed by CAISO to turn off power to approximately 200,000 to 250,000 customers at a time in rotating power outages. PG&E noted that rotating outages are not Public Safety Power Shutoffs, which are conducted during specific high fire threat conditions.

The utility subsequently said that Power has been restored to essentially all of the approximately 220,000 impacted customers.

Meanwhile, CAISO also directed SDG&E to initiate rotating outages throughout its service territory in San Diego and southern Orange counties.

“A total of about 58,700 customers were impacted in SDG&E’s territory by service interruptions. All impacted customers had their power restored as of 8:03 p.m. – about an hour and 20 minutes after the rotating outages began,” the Times of San Diego reported.

Approximately 132,000 of Southern California Edison’s five million customers lost power Friday night for about an hour, the Los Angeles Times reported, citing spokesman Robert Villegas. All of those customers had their power restored by 8 p.m., he told the newspaper.


The Los Angeles Department of Water and Power (LADWP) on Aug. 13 said that in addition to asking residential customers to save energy, LADWP was also implementing a Demand Response event with its commercial customers in response to a CAISO Flex Alert. The alert asked all power customers to save energy from 3:00 p.m. to 10:00 p.m. on Friday, August 14.

LADWP’s Demand Response is an incentive-based, voluntary program designed for businesses that helps reduce their utility bills during periods of peak power demand and helps to ensure the continued reliability of power service for Los Angeles.

LADWP said in an Aug. 15 tweet that the rolling blackouts implemented by CAISO on Aug. 14 did not affect residents of Los Angeles.

The public power utility noted that it owns its plants and transmission lines and had enough supply to meet demand and required reserves.

LADWP, “which has never had to implement rolling blackouts due to excess demand, was able to sell 225 megawatts to California ISO between 5 and 9 p.m., spokesman Joe Ramallo said,” the Los Angeles Times reported.

On Aug. 16, LADWP said that while it has adequate supply to meet its customer demand and emergency reserves “at this time, we join CAISO in urging customers to conserve energy to help the state grid and reduce the strain on neighborhood distribution systems. Extreme heat conditions, including very high nighttime temps that provide little relief to strained equipment, can cause equipment to fail, leading to power outages.”

LADWP also said on Aug. 16 that its crews had been working around the clock to restore small localized power outages caused by extreme heat and electricity demand. “Crews are working as quickly and safely as possible, and will work around the clock responding to outages.”  As of 5 p.m., approximately 4,800 customers out of 1.5 million total were without power.


The Sacramento Municipal Utility District (SMUD) on Aug. 16 said it was asking customers to limit their use of electricity during this week’s high temperatures, which are expected to continue into next weekend.

“With the heavy use of air conditioners, customers are using electricity at record levels, requiring the use of all SMUD power sources. With help from customers, SMUD expects to be able to avoid any power shortfalls,” it said in a news release.

SMUD noted it is a member of the Balancing Authority of Northern California (BANC), an independent balancing authority within the western electricity power grid. As a member of BANC, SMUD is not required to participate in rotating outages ordered by the California Independent System Operator (CAISO).

SMUD said it continues to support the statewide electricity grid in the event of a true electrical emergency.

During the heatwave, SMUD is all hands on deck with extra personnel available to restore power outages as safely and quickly as possible, it said.

CAISO requested power outages on evening of Aug. 15

CAISO declared a Stage 3 Electrical Emergency at 6:28 p.m. on Saturday, Aug. 15, due to increased electricity demand, the unexpected loss of a 470-MW power plant the and loss of nearly 1,000 MW of wind power.

IOUs in the state were directed to initiate rotating outages.

The load was ordered back online 20 minutes later at 6:48 p.m., as wind resources increased.

CAISO issues flex alert

On Sunday, Aug. 16, CAISO issued a statewide flex alert, a call for voluntary electricity conservation, through Wednesday, Aug. 19. The Flex Alerts are in effect from 3 p.m. to 10 p.m. each day.

“A persistent, record-breaking heat wave in California and the western states is causing a strain on supplies, and consumers should be prepared for likely rolling outages during the late afternoons and early evenings through Wednesday. There is not a sufficient amount of energy to meet the high amounts of demand during the heatwave,” the grid operator said.

“However, consumers can actively help by shifting energy use to morning and nighttime hours and conserving as much energy as possible during the late afternoon and evening hours,” CAISO said. “Consumer conservation can help lower demand and avoid further actions including outages, and lessen the duration of an outage.”

Consumers were urged to lower energy use during the most critical time of the day, 3 p.m. to 10 p.m., when temperatures remain high and solar production is falling due to the sun setting.

Extended periods of heat also can cause generator equipment failures that can lead to more serious unplanned losses of power, the grid operator noted.

Lightning strike to Alameda Municipal Power substation knocks out power to customers

Meanwhile, Alameda Municipal Power reported on Aug. 16 that lightning struck one of its substations causing a power outage to 10,000 customers.

Alameda Municipal Power subsequently reported that it had restored power to all but 50 customers on Aug. 16.