California was beset by its first rolling blackouts since the 2001 energy crisis, as a heatwave slammed the Western U.S. Friday and Saturday. Electricity demand for air conditioning throughout the region stretched California's power capacity and limited the state's ability to import power from nearby states.

But the blackouts were also a side effect of the state’s increasing shift to solar power and away from natural-gas-fired generators, according to state grid operator CAISO and Wood Mackenzie analysts. This shift pushed back the moment of “net peak” demand on the state’s grid — a measure of total demand minus renewable energy's contribution — into later in the evening, leaving CAISO with less dispatchable generation to fill in shortfalls between supply and demand. 

With high heat and peak electricity demand expected to continue throughout the week, California may be forced to rely on rolling blackouts for the immediate future, CAISO President Stephen Berberich said in a Monday meeting. Gov. Gavin Newsom declared a state of emergency on Monday allowing backup generators, including those deployed to customers facing wildfire prevention blackouts, to be used to combat outages, and demanded an investigation into the causes of the grid shortages.

But without changes to how the state manages its grid capacity needs, the same shortfalls could plague the state for years to come, Berberich said, in a scathing attack on what he called California policymakers’ failure to prepare for this eventuality. “The situation we are in could have been avoided,” he said in Monday's meeting. CAISO has told regulators for years that “there is inadequate power available during the net peak, the hours when the solar [generation] has left the system.” 

Friday and Saturday’s rolling blackouts, or “Stage 3 Electrical Emergencies” in CAISO parlance, forced utilities to cut off power to hundreds of thousands of customers between the hours of 6 p.m. and 8 p.m. Those are the hours when solar generation drops to zero, leaving CAISO with a “net peak” that comes one to two hours after its peak demand hour on the system. 

Why more solar can't help solve California's "net peak" problem

CAISO’s peak demand levels over the weekend were lower than its historical highest peaks in 2006 and 2017. But “the operational challenge that we face now is more around that net peak event,” Berberich said, which includes accounting for increasing demand from rooftop solar-equipped customers as their own self-supplied solar power dissipates. “That solar resource is fading fast, and we have to ramp up other resources quickly to meet that net peak event.” 

California has also lost a good deal of the generation capacity that it had in years past, Berberich noted. “In 2006, we had a lot more capacity on the system,” including the now-closed San Onofre nuclear power plant and thousands of megawatts of natural-gas plants that have since closed. California is set to close even more gas-fired power plants in the coming years, including several coastal plants targeted for retirement to reduce their harmful effects on marine ecosystems. 

Wade Schauer, Americas research director at Wood Mackenzie Power & Renewables, noted that California has shut down about 5 gigawatts of dispatchable generation since 2018, while it has only added about 2,200 megawatts of “non-intermittent” generation since then. 

California “just hasn’t done enough to keep resource adequacy where it should be, and the reserve margins have gotten tighter more quickly,” Schauer said. The chart below from WoodMac indicates how California’s total generation capacity has fallen below both gross peak and net peak needs, leaving a gap that must be made up from imports from other states.

Many of those states have retired their own generating capacity in recent years and are experiencing the same heat wave, so they have been unable to provide CAISO the level of additional supply it needs, Schauer added.

CAISO’s 2020 Summer Loads and Resources Assessment (PDF) noted that its system saw 1,926 megawatts of dispatchable capacity retire from June 2019 to June 2020. While it has added 3,423 megawatts of capacity over the same time, only 1,734 megawatts of that is dispatchable. CAISO does have access to about 1,300 megawatts of demand response to reduce peak demand and can call on customers to reduce energy, but those steps weren't enough to mitigate the shortages on Friday and Saturday. 

That assessment also pointed out that CAISO's daily peak period has “shifted to later in the day when solar generation is near or at zero levels, resulting in the CAISO’s highest demand levels being supplied by the remaining non-solar fleet. With lower than normal hydro conditions, the CAISO may have to rely more heavily on imports from neighboring [balancing authorities] during the CAISO summer peak hours. However, if a heat wave occurs that impacts a broader area than [the territory of] CAISO, the availability of surplus energy to import into the CAISO could be diminished.” 

More rolling blackouts to come 

Berberich said in Monday’s meeting that CAISO has “pointed out in filing after filing that the load procurement system was broken and needs to be fixed” to cover the hours when California’s solar resource fades to nothing while homes and businesses remain heavy users of air conditioning. 

CAISO’s warnings went unmet from the California Public Utilities Commission, which regulates how utilities procure generation assets and sets the rules of the state’s Resource Adequacy program to assure grid reliability, he said. CAISO’s warning last year that the state would experience a shortfall of 4,700 megawatts of resource adequacy by 2022 was met by a CPUC decision to require utilities to procure 3,300 megawatts of resources by 2023, an amount Berberich said is inadequate. 

CAISO was able to meet peak demand during the 2017 heat wave largely through imports from other states that weren’t experiencing the same heat, Berberich said. But CAISO has warned “time after time that imports are drying up,” a prediction that came true on Friday and Saturday “because the rest of the West is hot too.”  

The CPUC’s order for utilities and other “load-serving entities” such as community-choice aggregators to procure 3,300 megawatts of resource adequacy has so far been met with contracts to build battery systems to store solar power for injection into the grid in the evening. CAISO has about 200 megawatts of storage interconnected to its system at present, and all indications are that it performed well in playing a role in meeting CAISO's needs, Berberich said.

Expanding that energy storage capacity can help shift solar power into the evening hours now facing grid shortages. But “batteries [alone] won’t fix this problem,” he said, since they can’t generate their own power. “Solar power will have to be overbuilt to charge the batteries” as well as provide power to the grid. 

Implications for 100 percent carbon-free energy goals?

Berberich's comments underscore the debate over how states like California can reach their 100 percent carbon-free energy goals without relying on fueled generators to provide emergency grid capacity.

Recent studies indicate that reaching a 90-percent renewable grid and relying on natural gas for the remaining 10 percent of power is economically feasible by the mid-2030s. But converting the power grid to run entirely on renewable resources could be much more expensive, since such a path may need to rely on building excess solar and wind capacity and battery storage to cover shortfalls such as those the state is now facing. 

“For those who say we can rely on our reserves, you are wrong,” Berberich said in response to criticism that CAISO called its emergencies while it still had reserve generation capacity available. CAISO must retain its roughly 3,000 megawatts of reserve capacity to prevent the possibility of an even more widespread grid collapse, which could occur if a power plant were to drop offline or a key transmission line were to be forced out of service, he said. 

Similar conditions could force more rolling blackouts in California through this week.

“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,” CAISO wrote in a Sunday statement instituting a “Flex Alert” asking Californians to conserve energy from 3 p.m. to 10 p.m. to reduce load on the grid. 

CAISO is calling for help from other utilities across the Western U.S., and has secured commitments from the Los Angeles Department of Water and Power, U.S. Department of Defense facilities, and industrial and commercial entities to reduce demand. Still, it could face the need to call for hundreds of megawatts of rolling blackouts starting around 3 p.m. on Monday, and up to 4,000 megawatts starting around 7 p.m.. 

“We are scouring every corner of our world” for additional capacity, Berberich said. But the persistent heat across the Western U.S. has left neighboring utilities and generators with little to spare.