California ISO says grid better positioned for this summer, but reliability risks remain

May 18, 2021

by Paul Ciampoli
APPA News Director
May 18, 2021

The California Independent System Operator (CAISO) expects electricity supply conditions for the upcoming summer to be in better shape than last year, but the power grid is still susceptible to stress during extreme heat waves that extend across the West, according to the CAISO’s summer outlook released on May 12.

The 2021 Summer Loads and Resources Assessment projects the energy grid will have more capacity to meet demand in 2021 than it did in 2020, “a critical element for averting rotating power outages, such as those that occurred last August,” CAISO noted in a news release.

CAISO’s annual summer assessment evaluates expected supply and demand to help prepare for the hot weather months of June through September.

CAISO said the additional capacity is the result of resource procurement ordered by the state. A series of market redesigns and policy changes in CAISO’s system taken since September 2020 along with improved communication and coordination protocols has improved overall preparedness for this summer, it said. “However, if heat events similar to those that gripped the western states region last summer occur, imported energy from other states could be limited, and the power grid will be at risk of supply shortages and possible emergency conditions,” the grid operator said.

This year’s outlook includes roughly 2,000 megawatts (MW) of additional, readily available resources coming online to serve ISO net peak demand compared to this time last year, including battery storage that is expected to absorb excess renewable energy in the middle of the day, and inject it back into the grid after sunset when solar generation goes offline, the grid operator said.

The state and CAISO are continuing to pursue other opportunities to add an additional 1,000 to 1,500 MW of new resources to the system by summer.

The 2021 forecasted peak demands are about the same as last year under normal weather conditions.

However, extreme heat events are becoming more likely.

By incorporating last August’s historical heat wave into the assessment, it pushes weather previously regarded as extreme into what is now considered more normal ranges, CAISO noted.

The grid operator reported that California’s hydroelectric energy supplies will also be significantly lower than normal, with the state weathering a second consecutive year of below normal precipitation. Snowpack water content peaked at 60 percent of normal, similar to last year’s conditions, and reservoir levels have decreased to 70 percent of normal.

Meanwhile, imports will play a substantial role in this summer’s power grid reliability.

The assessment measured the likelihood of energy deficiencies and system emergencies, finding that at typical import levels based on historical data, there is a low probability of grid stress. But results based on analyses of more limited import levels associated with a widespread heat event showed that the probability of having to rely on measures to reduce load during emergency conditions, including rotating power outages, increases significantly during high demand conditions.

“Conservation will be pivotal to cushioning the grid when it needs it the most, typically during hot summer evenings when demand remains high for air conditioning use and solar production is going offline,” CAISO said.

In coordination with the California Public Utilities Commission, CAISO will issue Flex Alerts when system conditions are forecast to be tight, as it has done in prior years. Flex Alerts are voluntary calls to consumers to cut down on electricity use from 4–9 p.m. The state and CAISO are planning to launch a refreshed Flex Alert campaign in June to alert residents earlier of a potential supply shortage and spread the conservation message more widely.

Grid stability will also be improved through expanded communications and coordination among utilities and stakeholders in the state and across the West, CAISO said. The CAISO and its partners will continue to seek out and use extraordinary measures during emergencies, in an effort to avoid rotating outages, it added.

Elliot Mainzer, President and CEO of CAISO, discussed the state power grid’s summer outlook in an episode of the American Public Power Association’s Public Power Now podcast.