Originally Posted by Cobb
So, any feed back on use? Does it provide any real cooling effort? Any noticeable power savings? Does it run all the time or off and on like the fridge? Does it seem to be all on or off or does it seem to ramp up and down as heated water is needed?
We saved like 20 bucks a month with a timer on our electric water heater. Its on for 12 hours off for 12 hours. We also put a jacket on it and pipe insulation on the exposed pipes.
It turns on and off like a fridge.
It seems fairly well insulated and doesn't seem to need to cycle on very often.
I don't use large amounts of Hot Water in the 1st place .. 5-10 min showers .. soo I leave it in Heat Pump only mode all the time .. It takes a bit longer to recover all the hot water in heat pump only mode .. but I never use up the hot water capacity it has anyway.
It isn't a large cooling effect .. but , it's directly proportional to the amount of hot water one uses .. and I don't use a large amount of hot water .. if you use more hot water you would get more cooling effect.
But we can crunch some number estimates to put a 'face' on it so to speak.
There are two ways to do that .. the 1st is probably the easiest .. but also the most crude estimate .. it and an air conditioner are both heat pumps .. While actively heating the water .. it's maximum heat pump rate is about ~550W .. which at most maxes out up around like a ~5,000 BTU Window type (110vac) Air conditioner .. Except the heat removed from the air is stored in the hot water .. instead of being thrown away outside .. but it will only run for as long as it takes to heat the water to the selected temperature.
The second method expands on the above with more numbers .. and math.
It's estimated to use 1/3 of the electrical energy of a resistance based (~99% Efficient) electric water heater to heat the same amount of water the same amount .. soo at least a minimum of 2/3 of that hot water joules coming out of heat in the air that it removed.
Water has a specific heat value of ~4181 J/kgK .. and a density of 1,000 kg/M^3 ... soo .. If the initial input cold water were ~20C (~68F) .. to raise that up to 50C (122F) .. that 30C(30K) change in temperature would take about 125,430 J per Kg of water .. My unit has a 65 Gallon 1st hour rating .. but only holds up to 50 gallons .. which is about ~190 kg of water .. which would be at most about ~23,831,700 J of stored thermal energy in that 50 gallons of hot water .. at least a minimum of 2/3 of that came out of the air ~15,887,800 J .. or ~4,400 wh of heat energy removed from the air ... for every 50 Gallons of hot water per day taken from 20C(~68F) to 50 (122F) ... If it were concentrated over a short period of time that might be allot of cooling .. but it's spread out of the entire day .. and I don't use any where near that .. I use far less than that .. I'm at about 10-20 Gallons a day range .. Soo I might see around ~1,300 wh of air cooling effect over the course of a day .. not allot .. but , a free side effect of using 1/3 of the energy a conventional electric water heater would have used.