A 284L (75 gallon for the metrically-challenged) stores over 16kWh of energy when water is warmed from 10C to 50C. At a cost of around $450, the $28/kWh cost of using water to store energy beats battery options like the Tesla Powerwall by more than an order of magnitude.
Existing timers don't adjust for daylight saving time, and don't allow using cheap off-peak power during holidays. With increased use of renewable power like wind and solar, surplus power has become available outside the traditional nights and weekends. Some utilities have started using voltage optimization for grid demand management. Intelligent switches that respond to these voltage changes would allow for a more adaptive grid and more effective use of renewable energy.