Re: Smart water heater device
Adequate insulation is definitely the key to energy savings. However, if your water heater is within the conditioned envelope of the home, energy lost through radiation to the surrounding environment is not wasted in the winter when you're heating anyway. However, if you have a naturally aspirated (read: not a super-high-efficiency) water heater, every time it runs there is significant heat loss up the flue. Since your furnace likely is more energy efficient in terms of heating the air than radiation from your water heater, it's a good idea to minimize radiant energy loss from the water heater by beefing up the insulation.
The principle of turning the thermostat down and back up is based on the fact that energy loss is greater when there is a greater temperature differential between that which is being heated and the surrounding environment. If the water heater is allowed to cool down during periods of disuse, the energy loss decreases as it cools. Even with the need to run the water heater for a longer period when demand returns, the overall energy loss during the time of disuse is less than if the water heater's temperature was maintained. If you timed the cycling of the water heater, comparing maintained temperature with setback temperature, you should find that the "on time" is less for the period when a setback temperature is used. The difference will be more noticeable the cooler the water heater is allowed to get.
The device in question may provide a "learning" ability, like the Nest thermostat, that figures out what your usage patterns are. However, the cost of the device is likely to be so great that it may take several years to get a return on investment. A simple timer with a static program is much cheaper (though I don't know if they are available for gas water heaters) and will realize a much quicker return on investment.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.