Working with some power companies in Australasia, I found out there are actually water heaters which receive a signal over the power lines to turn off and on. Y

Working with some power companies in Australasia, I found out there are actually water heaters which receive a signal over the power lines to turn off and on. You would make an agreement with the power company for a lower rate, and a total amount of hours on per day (plus more details). The power company would then schedule your water heater in off peak times. This was more of a method of managing peak load, however, still seems applicable.