By Steve Gorman
LOS ANGELES (Reuters) - California's power grid operators warned homes and business on Monday to conserve electricity as rising demand for air conditioning stoked by a record-setting heat wave across the U.S. Southwest tested the region's generating capacity.
The so-called Flex Alert was posted until 9 p.m. Pacific time during a second day of triple-digit temperatures expected to strain Southern California's energy production, creating the potential for rolling blackouts on the first official day of summer.
The alert marked the first big test of power generators' ability to meet heightened energy demands in the greater Los Angeles area without natural gas supplies normally furnished by the now-crippled Aliso Canyon gas storage field, effectively idled since a major well rupture there last fall.
Southern California Gas Co, the division of San Diego-based utility giant Sempra Energy that owns Aliso Canyon, remains barred from refilling the underground storage reserve until the facility is deemed safe to operate again.
The gas leak at the site, the worst-ever accidental methane release in the United States, forced thousands of nearby Los Angeles residents from their homes for several months.
The leak was finally plugged in February. But with Aliso Canyon effectively shut down indefinitely, state energy regulators have warned that the region faces up to 14 days of gas shortages severe enough to trigger blackouts this summer.
The California Independent System Operator (ISO), which runs the state's power grid, urged consumers on Monday to cut back on electricity usage, especially during late-afternoon hours.
Utility customers were advised to turn off unnecessary lights, to set air conditioners to 78 degrees Fahrenheit or higher, and to wait until after 9 p.m. to run major appliances, such as clothes washers and dryers.
Much of the Desert Southwest simmered in a second straight day of record, triple-digit temperatures, as the National Weather Service extended excessive-heat warnings through Wednesday for southern portions of California, Arizona and Nevada.
Electricity demand on Monday and Tuesday was expected to top 45,000 megawatts, compared with last year's peak demand 47,358 megawatts last year and the all-time high of 50,270 megawatts in July 2006, according to the ISO.
All customers, including homes, hospitals, oil refineries and airports, are at risk of losing power at some point this summer because a majority of electric-generating stations in California use gas as their primary fuel.
Since the energy crisis of 2000-2001, the ISO has imposed brief rotating outages in 2004, 2005, 2010 and 2015, mostly related to unexpected transmission line or power plant failures during periods of unusually high demand.
Aliso Canyon is the biggest of four SoCal Gas storage fields and the largest such facility in the western United States. It provides service to the region's 17 gas-fired power plants, hospitals, refineries, and other key parts of California's economy, including 21 million residents.
SoCal Gas strives during summer to completely fill the 86.2-billion cubic feet (bcf) of storage capacity at Aliso Canyon to prepare for the upcoming winter-heating season, when gas demand peaks.
State regulators, however, ordered the company in January to reduce the amount of working gas in Aliso Canyon to just 15 bcf and use that fuel to ease the risk of gas curtailments and power interruptions this summer.
The utility is prohibited from injecting more fuel into Aliso Canyon until the company inspects all of its 114 wells.
(Reporting by Scott DiSavino in New York; Writing and additional reporting by Steve Gorman in Los Angeles; Editing by Joseph Radford)