Here is what I am thinking of doing. I want to add a small electric tank water heater to the outlet of my large hot water heat pump. This would allow me to turn the heat pump down to, say, 100 degrees and then the small tank would only have to heat the water up a small amount. This would cut down on tank losses and then the heat pump would not have to heat 80 gallons up to 125 degrees, it would run more efficient. I am looking at a 12 gallon little guy to attach to the 80 gallon big daddy.

Right now my 80 gallon tank is set at 125+ degrees. My usage is way up to 6 kW hours a day. If I reduced it to 100 degrees the saving would be about 40%. I will have to guess tank losses would be maybe 5% reduced. Maybe more, I don’t know for sure. For easy of numbers I will assume 3kW hours are saved. But how much will the little guy use?

With a 1500 Watt heating element I can heat 30 gallons of water up by 20 degrees in one hour. My shower head flows about 2 GPM. Of that 1.5 GPM is hot water. If I use 10 gallons from the little water heater that only gives me a 7 minute shower before I start to reduce my shower temp. (Mixing 125 degree water with 60 degree cold, darn anti-scald valve!) But, I could turn the little tank up to 145 degrees. Then I am up to… only 10 minutes.

Maybe I just need to look at the problem. The shower, I bet I could get one of those tankless under the sink models. Since the wife is the one complaining, not liking that word but that is what it is, I have to do something. I wonder if they make a 120V tankless for under the sink? Yes, set the heat pump at 110 degrees and the shower at 120. Then I could get rid of that useless hot water circulator pump. I will have to investigate further.

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