4.4kW of PV supplies all our electricity (plus ~10%), and hot water comes from an AC Wand(TM) water heater by butlersunsolutions.com (BSSI). We have a two-tank system with two 40-gallon tanks connected so they convect naturally to heat the upper (pilotless, gas-fired) tank. The bottom tank has the BSSI AC Wand(TM) heat exchanger that heats the tank from a 120VAC outlet (~625W). This keeps the water heater above the setpoint of the gas burner, so it does not fire up.
Since it has no pilot light we can go for days without using any gas