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Rolling blackouts that had been forecast were averted Monday and Tuesday thanks to large and small customers who slashed their energy use.

Peak demand on Monday dropped more than 4,000 MW below the projected high of 49,827 MW.

“The response was stunning,” Steve Berberich, California Independent System Operator president and chief executive officer, said during a Tuesday press call. The conservation was across the board, from large industry to households.

The Aug. 18 peak also was below the forecast, reaching 47,121 MW. That is far lower than the projected peak demand of 50,485 MW. The highest peak to date occurred on July 24, 2006, soaring to 50,270 MW.

“Californians made tonight a success,” Berberich said Tuesday evening after CAISO called off the Stage 2 power alert.

In addition to widespread conservation, Tuesday’s power peak also was shaved by an increase in imports—1,500-2000 MW more than the day before.

Accompanying the spike in peak demand and potential outages Monday and Tuesday were huge price increases in the day ahead market. They soared to $1,500 a megawatt hour in San Diego Gas & Electric and Southern California Edison territories. Meanwhile, they reached $400 MWh in Pacific Gas & Electric territory.

The overall system price in the day ahead market reached $1,000 MWh, said Mark Rothleder.

CAISO Day Ahead Prices for Aug. 17 and Aug.18

The $1,000 MWh is expected to be seen in the real time market at peak hours as well, added CAISO's vice president of market policy and performance. Rothleder also said Tuesday that it is not unusual to see price spikes during high load hours. He acknowledged they were considerably higher in Southern California, saying it was probably driven by transmission constraints in the area.

CAISO caps prices at $2,000 MWh.

CAISO prepared for more rolling blackouts

On Aug. 17, the grid operated announced that the three private utilities may have to cut power to more than 3 million to keep the grid from collapsing. It warned there was a likely 4,400 MW shortfall. With actual peak demand at 45,169 MW on Monday, rolling outages were called off.

CAISO warned that projected demand on Tuesday would exceed the supply by 2,700 MW starting mid-afternoon. But the actual peak was about 3,600 MW below the 50,485 MW forecast.

The system capacity is 46,000 MW while the sun shines, according to the grid operator. It drops to 43,000 MW after sunset.

Some blamed the supply constraints on California retiring too many large natural gas fired power plants and replacing them with renewable resources.

Berberich disagreed. “This is a resource issue, not a renewables issue.” He attributed the supply-demand imbalance to resource shortages across the West, which, in turn, he said were due to closures of uneconomic coal-fired plants.

CAISO called for continued power conservation through Wednesday because of the lingering heat wave.

Peak demand for Wednesday was forecast at 47,382 MW.

Extreme temperatures were predicted to extend through Thursday in Southern California. After Wednesday, Northern California temperatures are expected to drop from their extreme highs.

CA's first Stage 3 since 2001

Friday, Aug. 14, was the first time since the energy crisis that CAISO called a Stage 3 emergency.

It was the first of several days of triple-digit weather in and outside California, with peak demand hitting 46,721 MW. Almost 1,500 MW of power went offline late that afternoon. A 450 MW gas fired plant unexpectedly shut down and 1,000 MW of wind fizzled in the heat.

The outages were in effect for about an hour Monday evening. That was partly because the wind began to blow; there was 800 MW of savings from demand response, and another 225 MW was provided by the Los Angeles Department of Water & Power, which is outside CAISO territory.

Continued supply and demand imbalances caused rolling blackouts in the three investor-owned utility territories on Saturday too.

Pacific Gas & Electric turned off power to approximately 220,000 customers the evening of Aug. 14 to help relieve the strain on the power grid during the heatwave. The first customers were affected around 6:30 p.m. Power was restored to most customers within a few hours; all had power back by 10:15 p.m., according to PG&E.

Southern California Edison as directed by the CAISO also cut off power. Its rolling blackouts on Friday affected about 132,000 customers for close to an hour. The next day, the utility cut off power to approximately 70,000, this time for just 18 minutes.