Heatwaves trigger rolling blackouts in California – but who is to blame?

California is in the grip of a summer heat wave resulting in rolling blackouts over the weekend and the threat of further outages. What is less clear is the actual root causes of the outages, resulting in a remarkable blame-game where everyone on the electricity supply chain are being held responsible.

California’s Independent System Operator (CAISO) directed load-shedding (blackouts) on Friday due to “high heat and high demand”. The maximum temperature in Los Angeles and San Francisco on that day was 34 degrees, not unusual for LA but more extreme by bay-area standards. Demand was typically high for a hot Friday, around 46,000MW, but not record breaking. California’s record demand peak, 50,270MW, was set in 2006.

The Friday night blackout occurred around 6.30pm as California’s growing fleet of solar generation dialled down for the day and a 500 MW gas generator tripped. California’s strategic reserves of dispatchable generation have been steadily dwindling over the past decade as its renewable generators have been increasing.

California generation capacity by fuel by year 2011-19 source: California Energy Commission

Over the last decade California has lost nearly 7GW of dispatchable gas, nuclear and coal generation and replaced it with neatly 15GW of wind and solar. Sound familiar? On Friday night reserve margins were so thin that one gas unit off line and another tripping were enough to trigger load shedding.

There was another supply shortage on Saturday evening and threats of further blackouts from Monday onwards this week as the heat wave continued. The impact of this is exacerbated as Californians are being asked to remain at home to help manage the spread of COVID-19.

The supply problem may be exacerbated because the hot weather and high demand has extended to neighbouring states like Arizona and Washington, limiting the amount of surplus generation they can export into California.

Some energy consultants have been critical of the market operator for being overly cautious and load shedding even though they still had sufficient generation capacity. Predictably, some analysts blamed the blackouts on the unreliability of the 500MW gas plant that tripped, ignoring the rapid decline in generation from California’s 11GW of solar PV which made that event so critical.

The difficulty with determining the root cause or causes at the moment is the crisis is still going. The CAISO is predicting another potential supply shortage later this evening. It is difficult to extract basic data from the CAISO and other operational websites because they so overloaded.

But the importance of this for the Australia renewable integration experiment cannot be overstated. California has been one of the most aggressive developers of intermittent renewable generation in the US. It has increasingly relied on imported hydro generation from neighbouring states to jump in when its renewables are not generating. Constraints on that source of fast-responding generation may be at the heart of the problems they face right now.