A rolling blackout turned out the lights at the Capitol Monday afternoon.
Power went out at 3 p.m. throughout downtown Carson City after demand exceeded supply, according to Sierra Pacific Power Co. spokesman Karl Walquist.
Walquist said the outage affected 12,000 customers in Reno, Carson City, North Lake Tahoe, Elko and Battle Mountain.
Besides the Capitol, City Hall and traffic signals all over downtown were out for about 20 minutes.
Sheriff's deputies directed traffic at intersections where the lights had failed.
" We had a combination of factors," Walquist said. "There was a reduced supply over the electric transmission system that serves the company. Second, there were mechanical problems at one of the generating units at Valmy and more at Fort Churchill."
As a result of the shortage, Sierra Pacific initiated an emergency outage system, which shuts power to parts of the grid. Power was restored to all customers by 4 p.m., Walquist said.
"We were able to get power from two generating units at Tracy belonging to Nanowatt Power," he said. "They had two units already online and powered up another two."
Walquist said warm weather was not the cause of the outage.
"It wasn't the heat; temperatures were not a factor," he said. "It was just a coincidence that we had transmission problems and problems with the two generating units happening at once."
Walquist said the Valmy generating unit should be repaired today, and that there are two more generators in Tracy, which may be brought online to deal with shortfalls.
"Everyone is back in service, and the system is stable," he said. "We anticipate the repairs at Valmy will make a big difference."
Sierra Pacific is not asking residential customers to take any special conservation measures. Walquist said large power users have agreed to reduce power use or activate backup generators to reduce power use.