This may be a small tangent, but, another point to consider is the use of a diversion load from a solar/wind charge controller. This diversion load circuit can include a 12v heating element installed in the hot water tank in place of the 110v element. Once the charge controller satisfies the battery banks, it diverts usable voltage to the diversion load. This is something I am considering but have not yet tried or even fully investigated. How efficient is this (no idea)???....but it does seem logical not to waste the electrical potential when available.
1983 Morgan OI 416