The nuclear shutdown at San Onofre is partially to blame for a 59 percent increase in wholesale electricity prices for California in the first half of the year, the Energy Information Administration said Tuesday.
The statistical arm of the U.S. Department of Energy found that wholesale electricity prices rose across the country during the first six months of 2013 over the same period last year.
Prices in New England were the highest largely because of pipeline constraints that limited the delivery of natural gas.
In California, the "increase was largely the result of the continued outage of the San Onofre Nuclear Generating Station," according to the agency's Today in Energy briefing. "This factor also caused a large and unusual separation in power prices between the northern and southern parts of the state's electric system."
M. Tyson Brown, a statistician at the Energy Information Administration, clarified that a modest rebound in historically low natural gas prices has been the main driver of the overall increase in wholesale electricity in California. Natural gas generation is California's principal source of electricity.
Since the San Onofre outage began in January 2012, however, there has been a persistent spread between wholesale power prices in Northern and Southern California, Brown explained.
"The Southern California prices have been a good deal higher than the Northern California prices," he noted.
The layout of California's transmission grid limits the amount of power that can be transferred between the north and south of the state.
Wholesale price increases are likely to translate into higher average utility bills. Commodity costs for household electricity and natural gas in California are generally passed on directly to customers, but require regulatory approval before the utility can change rates.
Electricity costs account for about half of the electrical portion of monthly bills on average, according to San Diego Gas & Electric. But the impact of wholesale prices on consumers is hard to estimate precisely -- especially under complex residential rates.
San Onofre's two nuclear reactors, which once produced enough electricity to power 1.4 million homes, were taken off line in January 2012, never to return. The plant's operator gave up in June on efforts to resolve problems of rapid wear on faulty replacement steam generators.
California's main grid operator found that wholesale electricity prices fell just 2 percent in 2012 despite a nearly 30 percent drop in natural gas prices. The San Onofre outage -- along with lower hydroelectric supplies and shifting energy demands -- contributed to that price disparity, according to the California Independent System Operator.