12-03-2009, 02:06 AM
They do sell water heater timers for electric water heaters, primarily to shift the heating periods to off-peak periods, when electricity costs less. Gas timers would be more difficult and costly to implement and gas doesn't have peak/off-peak periods. The problem with doing daily timing is that once heated up, it does take quite a while for the water to cool down because the tank is insulated, so the energy savings wouldn't be that significant unless you're going away for more than a day or so.