Let me ask this simple question first… Is a geothermal hydronic heat pump (Water Furnace Envision Series 5) connected to a 120 gallon solar water heater tank (open loop system) worth having if the optimal temperature setting for the household is 135F degrees? (We keep it that high for dedicated lines to dishwasher and washing machine, before mixing down to 125F degrees.) Now more information… Since our system was installed a few years ago, we have always had to turn up the temperature setting on the water tank during the winter months. Call me slow, but it all the sudden dawned on me that the primary source of water heating is electric at the tank, verses the geothermal unit that I thought carried the main workload. This is because the Envision model only allows for temperature settings up to 130F degrees and it is "highly recommended” by my installer to keep the setting no higher than 125F degree for mechanical longevity. Logically, that means that the heating elements in the water tank kick in before the geothermal unit. Regardless, I see that the Envision is heating water regularly. What am I missing here? As for troubleshooting, my hot water lines need insulation in this huge old house. This causes the need for slightly higher water temperatures at the tank in order to keep the ideal temperature at the fixture. We also have a whole house hot water return line (hot water recirculator) that slowly siphons off water temperature and causes more need for periodic heating. I had already planned on replacing most all the old copper plumbing with PEX in the next year. This will get rid of the hot water return line and slightly decrease what the overall water temperature setting will be. Still, there is the issue of which source of water heating does the main work. My overall goal is to reduce the electricity used for hot water, as it is still quite high when I finally placed a power sensor on the circuit for a few days. Obviously, the whole point with the geothermal heat pump purchase was to reduce water heating electrical usage by making the Envision do most all of the work. It is still more efficient than the gas water heater tank that we had. So, is my basic assumption about the primary source of water heating correct? Any caveats? Any suggestions for increasing the efficiency of my geothermal heat pump over electrical heating? Peace, Dr. Z.