Hi.. I'm the guy with the pilot only set up.
12vman.com
My system works well because the input water temperature is around room temperature. I store my water in my living space during the winter so it doesn't freeze up.
If you were to pull water in from water lines in the ground, the input temperature would be about 52 degrees. It would take days for the tank to recover to a comfortable, usable temperature.
Gary did some calculations on how much energy my idea would use..
~Don