California Power Gains After Diablo Canyon Nuclear Reactor Shuts

California wholesale electricity gained as hotter weather lifted demand above forecasts and the unplanned shutdown of a Diablo Canyon reactor reduced supplies.

Spot prices rose for the first time in three days after PG&E Corp. shut Diablo Canyon 1, located about midway between Los Angeles and San Francisco, after discovering a socket weld leak, according to a Nuclear Regulatory Commission report. Power consumption topped yesterday’s outlook across the state grid.

Southern California’s SP15 hub, a proxy for Los Angeles and San Diego, rose $17.47, or 54 percent, to average $49.67 a megawatt-hour during the hour ended at 1 p.m. West Coast time from a day earlier, grid data compiled by Bloomberg showed. Yesterday’s day-ahead outlook for the hour was $50.92. The on-peak average is up 14 percent at $40.06.

Northern California’s NP15 hub, which includes deliveries to San Francisco, gained $11.01, or 29 percent, to average $49.39 a megawatt-hour, above the day-ahead price of $42.69. The on-peak average rose 14 percent at $43.60.

The discount for SP15 spot on-peak power versus NP15 widened to an average of $3.54 a megawatt-hour from $2.99 yesterday.

Repairs to Diablo Canyon 1 “will not be difficult or take very long to complete,” said Lara Uselding, a spokeswoman for the NRC’s Region 4 office in Arlington, Texas.

NRC data shows the unit was operating at 50 percent yesterday. Its capacity is 1,159 megawatts, according to the Energy Information Administration.

Power Use

Electricity consumption across the state was 36,109 megawatts as of 1:20 p.m., 5.5 percent higher than the day-ahead forecast of 34,216 megawatts for the hour, according to the California Independent System Operator Corp., which manages the grid.

New England prices reversed earlier gains as demand fell at a faster pace than expected. Prices also dropped from New York to North Carolina amid lower-than-forecast consumption.

Boston spot prices fell $30.09, or 44 percent, to $37.67 a megawatt-hour during the hour ended at 4 p.m. Eastern time, below the day-ahead price of $81.77 for the hour. New York City slid $86.12, or 67 percent, to $41.25 a megawatt-hour from a day earlier, below the day-ahead outlook of $123.76.

On-peak power for New York averaged a discount of $1.63 to Boston versus a premium of $14.09 yesterday.

Electricity at PJM Interconnection LLC’s benchmark Western hub, which includes prices from Washington to Erie, Pennsylvania, declined $17.68, or 29 percent, to $43.88 a megawatt-hour, below yesterday’s outlook of $88.14.

Midwest prices also dropped as consumption fell below the day-ahead forecast.

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