Sierra Pacific Power Co. issued a "yellow" power alert Monday as energy usage in northern Nevada climbed to record levels and problems at one plant hampered supplies.
With temperatures hovering at or above the century mark for the second straight day, power use climbed to an unofficial all-time high of 1,620 megawatts, said Michael Yackira, vice president of Sierra Pacific Resources and the parent company's two subsidiaries, Sierra Pacific Power and Nevada Power.
Last year's peak load topped at 1,590 megawatts, he said.
A yellow alert is issued when demand for electricity could exceed available supplies.
Yackira said large customers were asked to run their own generators. Residential and other business customers were urged to conserve power until 8 p.m. by turning off lights, setting thermostats on air conditions a degree or two higher and avoiding using large electrical household appliances, such as dishwashers, washing machines and clothes dryers.
Voluntary cutbacks could help avoid a "red" alert and rotating power outages, the company said.
Sierra Pacific's southern Nevada sister utility, Nevada Power Co., set a record for energy use, but reported normal operations with no supply or transmission problems.
"Part of it is that air conditioners have to work harder when it's humid," said Andrea Smith, spokeswoman for the Las Vegas-based utility. She said the 4,808 megawatts the utility's 680,000 customers were drawing at 4 p.m. eclipsed the previous record of 4,789 megawatts, set July 11.
Yackira said one unit of the company's Valmy coal plant east of Battle Mountain had to be shut down early Monday because of problems with a water pump.
Though the problem was fixed by midday, Yackira said it could take several hours, if not longer, for the plant to start up.
"Because it's a coal plant, these things take awhile to come back," he said.
A second Valmy unit has been shut down for about a month for major repairs, he said.
"Electrical power plants, as Murphy's Law has it, have a tendency to have problems when you need them," Yackira said.
Each unit at the Valmy plant, owned jointly by Sierra Pacific and Idaho Power, can produce 250 megawatts, Yackira said.
Sierra Pacific receives about half the output.
"Right now we're getting none," Yackira said.
A megawatt is enough electricity for about 600 homes.
With forecasters predicting triple-digit temperatures in northern Nevada at least through midweek, getting Valmy back" is critical to staying out of trouble," Yackira said.
About 45 percent of Sierra Pacific's power is generated internally. The rest of purchased from other suppliers.
"As long as transmission lines are available to us and power providers are not having problems, we can meet the load," Yackira said.
"Today, we are importing a significant amount of power," he said. So far, the units in the area have been performing well and delivering power into our transmission lines."
Sierra Pacific Power has about 323,000 customers in northern Nevada and eastern California.