California's Smoke Signals

California's Smoke Signals

San Francisco's power emergency is a warning about green mandates.

Governor Jerry Brown on Friday called a "state of emergency" in San Francisco because a distant wildfire threatens the city's electricity supply. Like so many other emergencies in California, this one is government-made and a warning about its green political obsessions.

The Rim Fire, which is slashing and burning through the Yosemite region, forced the San Francisco Public Utilities Commission to shut down two Hetch Hetchy hydropower plants and the transmission lines that power its municipal buildings. While a government shutdown in San Francisco might have salutary effects, the city's hospital, port and airport would also be affected. Hence the emergency.

The utility commission assured residents over the weekend that it doesn't anticipate service interruptions because it can purchase power on the open market—though so far at a $600,000 premium. The bigger disaster, according to the utility, is that it "has been unable to generate and transmit clean, greenhouse gas-free hydroelectric power" and must rely on natural gas-fired plants. This contravenes the utility's 100% renewable-energy goal.

The utility procures 97% of its power from Hetch Hetchy's 400-megawatt hydroplants via roughly 150-mile transmission lines. New-generation renewables such as solar and biogas supply a mere 10 megawatts of municipal power because they require more space and capital to bring to scale. Trouble is, long transmission lines are at high risk to disruption in natural disasters.

Most San Francisco residents and businesses get their power from PG&E, a private utility, so they don't have to worry about this risk now. But they shouldn't rest easy. Renewables make up 20% of PG&E's portfolio and under California law must comprise a third by 2020, and many state politicians want a 100% goal like San Francisco's.

To hit the renewable mandate, utilities are building long transmission lines to deliver power from distant solar and wind projects to population centers. Most large-scale solar plants in California are being built in dry, sunny desert and valley regions. Wind farms are concentrated in the mountains. Both are fire-prone.

Take San Diego Gas & Electric, which last year completed a 120-mile transmission line from Imperial County wind and solar farms at a cost of $1.9 billion. According to a 2008 draft Environmental Impact Report, "there were 33 reported power outages resulting from 16 distinct wildfire or lightning events" between 1986 and 2005 along an existing transmission line running through the valley.

The Little Hoover Commission, the state's oversight agency, warned last year that the closure of the San Onofre nuclear plant leaves Southern California "vulnerable to brownouts during heat waves" or "if a wildfire took out a key transmission line." California has usually had excess generating capacity to pick up the slack when transmission lines are downed. However, the excess capacity is declining as more renewables come online and gas-fired plants, which are located along the coasts near cities, are retired.

California may soon have a lot more fires to put out if Sacramento blazes ahead with its renewable mandates.

A version of this article appeared August 26, 2013, on page A18 in the U.S. edition of The Wall Street Journal, with the headline: California's Smoke Signals.