A natural gas-fired water heater on a Kasa HS-110 monitor was recently mentioned at Sense Saves (Again!) In that post, @ac.mackenzie11 explained yesterday that his model uses 1W when idle and approx 155W when the heater is running. I repeat that statistic here since it seems relevant to the above discussion.
I recently noticed something about my setup. I had known that the fan inside the unit continues to blow for a little while after the flame stops. The plumber who installed my water heater explained that manufacturers cause their units to do this on purpose. It exhausts any fumes remaining in the vent stack so that moist, acidic vapors don’t later condense and corrode things. What I just noticed is that this behavior is visible as a plateau at the tail of the Sense graph if you zoom all the way in:
This brings me to a potential disadvantage of creating a schedule for the HS-110 serving a gas-fired water heater, as I have done. The danger is that the “off” signal could come while the unit is in operation (ie, not idle). If so, safety circuits would surely close the gas valve so the flame would die, but the extra seconds of fan operation at the end of the cycle would not occur. While this happening once or twice should not be a problem, repeated instances could lead to the corrosion issue that my plumber warned me about.
I am curious about the experience of this thread’s original poster. @norenlaw, how is your setup working after the first month? You seemed interested in creating a detailed schedule, so the above comment may apply to you. In my case, I feel pretty safe with my schedule since my family typically showers in the morning rather than before bed.