Fifty residential electric water heaters and 150 new residential clothes dryers were modified to

respond to signals received from underfrequency, load-shedding appliance controllers. Each controller

monitored the power-grid voltage signal and requested that electrical load be shed by its appliance

whenever electric power-grid frequency fell below 59.95 Hz. The controllers and their appliances were

installed and monitored for more than a year at residential sites at three locations in Washington and

Oregon. The controllers and their appliances responded reliably to each shallow underfrequency event—

an average of one event per day—and shed their loads for the durations of these events. Appliance

owners reported that the appliance responses were unnoticed and caused little or no inconvenience for the

homes’ occupants.