I previously recommended the use of a controller for your water heater as a way of controlling power consumption. Now that I have the solar up and running, the Tesla app is a great way to monitor and check up on your electrical loads.
Now that I have the ability to do this, I am convinced that the Aquanta water heater controller doesn’t actually DO anything. Whether I am home or not, using hot water or not, the amount of electrical power that the Aquanta is claiming I am using to heat water doesn’t change, at about 15kwh per day. The only time the amount of power the Aquanta was claiming went down is when we put the system in “Away” mode- telling it to turn off the hot water while we were out of town. At that point, the Aquanta reported that we were using about 1 kwh per day. The only problem? The amount of power we were using for the entire household didn’t change, according to the Tesla app.
At this point, I began suspecting that the Aquanta is a random number generator. It reports to you how much money it is saving you, but isn’t actually doing anything. I decided to test it and see what was going on. I am going to make a serious accusation here, so let me state that I did all voltage readings using a FLUKE 115 True RMS multimeter.
I measured the voltage across the output of the Aquanta while it was in “efficient” mode with a green LED showing and got a reading of 249 VAC. The water heater uses power consumed of 4500 watts (4.5kw), so a little application of Ohm’s law results in 18 amps and 14 Ohms of resistance. We can directly use Ohm’s law because the water heater has no capacitance or inductance, it is a purely resistive load.
Then I put it into “Away” mode. The LED on the unit turned red, so I measured the output voltage and got 70 VAC. Another application of Ohm’s law using the same 14 Ohms we calculated before tells us that the water heater is now using 5 amps and 50 watts of power. Take that 50 watts of power and multiply it by 24 hours in a day, and you get about 1 kWH per day.
So it doesn’t shut off the water heater, it merely lowers the voltage from line voltage down to about 70 VAC. I am not sure when or how it does this, other than in vacation mode, but I don’t think I am saving any power.
I just don’t think that this is a good unit to use if you want to save power, so I am withdrawing my recommendation of the Aquanta unit. My recommendation is to either use an electro-mechanical water heater timer, or a smart pool pump relay.







