|D.J.Hammerstorm, Pacific Northwest National Laboratory|
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.