My house has a several renewable systems for power generation and heating. The PV system is a 10KW grid-tied battery backed up system. The heating and hot water system is an integrated one. It consists of 4 4’x10′ solar hot water panels, an outdoor wood fired boiler, and a geothermal ground source heat pump. I still have an old 40 gallon electric hot water heater assisted by a thermosyphon heat exhanger tied into the loop that is heated by the geothermal or solar or wood fired boiler. This hydronic system is tied into a radient floor and several hydronic baseboard heaters.