You might want to try running
low-heat mode, using 120 instead of 230 vac.
I checked out the heating elements with my new water heater and at 120Vac they use 1.130 kW. (3856 BTUh).
Or, if you have enough PV you can put in series to get up about 120 to 150 vdc,
that might pump in a few BTUh.. But, the AC grid would be a lot more reliable.
Nice thing about using a 120vac hotwater heater, timers are cheap!!
