California's electricity grid manager warned that power to large energy consumers is likely to be cut later Thursday to keep the state's lights on.
The companies that would go dark are a mix of industrial, commercial and retail businesses that previously agreed to be the first to lose power during an emergency. In exchange, the companies receive reduced utility rates.
"Having those customers come off the grid is just as good as adding power," said Stephanie McCorkle, spokeswoman for the California Independent System Operator.
Reducing power demand, however, is California's only choice. It cannot add power because its electricity plants are running at capacity and a heat wave is stressing power systems throughout the West.
The independent system operator, which manages the flow of energy on most of California's power grid, plans to declare a minor power emergency at 2 p.m. Thursday and to increase its alert level to a so-called Stage 2 emergency at about 4 p.m.
A Stage 2 emergency signals that the state's operating reserves have fallen below 5 percent. At that point, Pacific Gas and Electric Co., Southern California Edison and San Diego Gas and Electric Co., the state's largest investor-owned utilities, begin cutting power to the large companies with which they have arrangements.
The highest alert level is a Stage 3 emergency, which indicates that operating reserves have dropped below 1 percent. Rolling blackouts — in which power is cut to certain regions to avoid a systemwide crash — are imminent at that stage.
If the state reaches a Stage 2 emergency today, it will be its first since July 24, 2006, when California set its all-time record energy demand of 50,270 megawatts. Today's predicted peak demand is 49,572 megawatts.
McCorkle said increased energy conservation by individual consumers this afternoon could help prevent a Stage 2 emergency.
"We're really stepping up our calls for conservation; they do help," she said.
The Independent System Operator suggests setting thermostats at 78 degrees or higher, using fans to cool rooms, turning off unnecessary lights and shutting off large appliances from 2 p.m. to 6 p.m.
State officials say those whose health could be compromised should not put themselves at risk by shutting off air conditioning.
The state also has opened cooling centers at fairgrounds in eight Central Valley and Southern California counties. They will stay open until Tuesday, with hot temperatures forecast throughout the Labor Day weekend.
Most of California's vast Central Valley was expected to have temperatures well over 100 degrees, with parts of the Los Angeles region also forecast to hit 100. Much of the San Francisco Bay area was expected to be warmer than normal.
The state has established a toll-free telephone number to provide information about cooling centers, 1-877-435-7021.