Hi. While this is not really a “home automation” issue it is related, and I think you members would probably be best positioned for an answer. As a PV installer, our general approach is to split the main DB so that geysers, stoves and the like are treated as “non-essential” loads and fed directly from the grid. Lights, plugs and various other “essential” loads are fed from the inverter, in order to keep costs in check. I am pretty sure that most installers do it this way.
A problem I have come across numerous times is when you install a system in a house with out-buildings which have a single-phase supply fed from the Main DB in the house, but they also have a geyser (or stove). If you treat the outbuilding as non-essential, it has no backup power. If you treat it as essential, your risk overloading the inverter because of the geyser. The obvious alternative is to run another feed to the outbuilding, but this can be often be expensive and difficult.
I hoped there would be a way whereby a relay / geyser timer switch or the like, could be installed in the out-building geyser circuit to act as a switch, and could be controlled via wifi (or something else) from the main house so that it would switch off during outages. Thus the geyser no longer overloads the inverter, but the outbuilding has backup power. Does anybody know of a way to do this ?