San Onofre Nuclear Closure to Boost State Carbon Emissions by 8 Million Tons

Replacement Electricity Equivalent to Adding 1.6 Million Cars

The retirement of two nuclear reactors at San Onofre Nuclear Generating Station in Southern California, announced Friday, is expected to increase state carbon emissions by at least 8 million metric tons annually — the equivalent of putting 1.6 million new passenger vehicles on the road — according to a Breakthrough Institute analysis.

The San Onofre station, located near population hubs San Diego and Los Angeles, supplied about one-tenth of the state’s electricity needs, generating carbon-free electricity to the equivalent of 2.3 million homes each year.[1] Meeting the same demand with natural gas, which emits roughly 1.12 lbs of CO2 per kWh, would generate an additional 17.7 billion lbs, or 8 million metric tons, of CO2.[2]

In preparation for the closure, California’s grid operator (CAISO) added 2,502 megawatts (MW) of generating capacity in June, with 891 MW coming online this month.[3] The majority of this new capacity has been gas-fired power plants. Solar and wind have contributed to the added capacity, but to a much smaller degree.

Because of its strategic position between two urban centers and the quality of electricity it provided, replacing the electricity lost at San Onofre will not be as simple as building an equal amount of new gas, solar, and wind capacity. As the Energy Information Administration reported today,[4] new transmission upgrades will be needed to carry electricity from areas outside of the San Diego-Los Angeles area to those cities.

The fact that San Onofre has been replaced mainly by gas has significant implications for the Golden State’s climate goals. The additional emissions from replacement gas-fired electricity will make it more difficult for the state to meet its emissions targets and will encumber the state’s newly enacted cap and trade program.

The retirement of the two reactors, which make up about half of the state’s nuclear capacity, may signal a zero-carbon energy crunch in coming years around the country. The United States currently meets 20 percent of its electricity needs with nuclear, but the looming closures of plants licensed in the 1960s and 1970s in New Jersey, Wisconsin, and other states raise questions about how the country will be able to supply clean, baseload energy at the same or higher levels.

The two SONGS reactors were taken offline in January 2012: Unit 2 for a planned service outage and Unit 3 because of a small tube leak inside a steam generator.

The closure of San Onofre station could have been avoided if not for delays in the restart approval process. According to Southern California Edison, a restart plan for Unit 2 was submitted to the Nuclear Regulatory Commission in October 2012 but got held up in the review process by an adjudicatory arm of the NRC, the Atomic Safety and Licensing Board. Additional administrative processes and appeals would have resulted in further delays of more than a year, and the costs of keeping SONGS offline would have created major additional losses for the power company.[5]

The SONGS closure may also add to recent increases in the cost of electricity. The United States Energy Information Administration reports that the closure of Units 2 and 3 in January 2012 created a persistent spread in wholesale power prices between the Northern and Southern parts of the state.[6] On average since January 2012, Southern Californians have paid an additional $4.15 per MWh compared to Northerners.


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[1] According to the EIA, in 2011 the average annual electricity consumption for a residential utility customer in California was 6,804 kWh. With an average capacity factor of about 84% between 2009 and 2011, SONGS generated some 15.8 billion kWh each year. The Environmental Protection Agency estimates that the average car emits 5.1 metric tons annually.

[2] With a nameplate capacity of 2,150 MW and an average capacity factor of 83.8%, SONGS generated about 15.8 billion kWh of electricity to the grid each year.

[3] California ISO, “Summer Loads & Resources Assessment,” May 2013.

[4] Energy Information Administration, “New generators help California meet summer challenges to electricity reliability,” June 7, 2013.

[5] Edison International, “Southern California Edison Announces Plans to Retire San Onofre Nuclear Generating Station,” June 7, 2013.

[6] Energy Information Administration, “Extended nuclear power plant outages raise Southern California wholesale power prices,” March 26, 2013.