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. <a href="http://ecoralph.blogspot.ca/2011/04/saving-with-timers.html">Existing timers</a> 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 <a href="https://www.nema.org/Policy/Energy/Smartgrid/Documents/VoltVAR-Optimazation-Improves%20Grid-Efficiency.pdf">voltage optimization</a> 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.