HECO wants its customers to reduce their use of appliances, such as clothes dryers, dishwashers and air-conditioners, until after 9 p.m. today.

HECO spokesman Chuck Freedman said demand for power set a record Monday night, then set another record last night.

"With the muggy conditions forecast again for today, we may hit yet another new high tonight," Freedman said. "So we are calling on all customers to cut electricity use throughout the day as much as possible. Conservation will help."

HECO said its "reserves of power generation are very tight today."

Part of the problem is that two generators at HECO's Waiau power plant were shut down for unanticipated maintenance yesterday and the company has no idea when they will return to service.

But other generators are out as well. A third generator also is out of service for planned maintenance and the city's HPOWER unit is operating at reduced power because of planned maintenance.

HECO said that if it lost another generator or if demand was too great, it would have to systematically shut down power to "blocks of customers" to maintain the stability of the power system.

The procedure, which it dubbed "load shedding," is designed to ensure that hospitals, secure facilities and key public safety organizations have electricity.