[Ryland]

When I wired up my parents house I added low voltage wiring, the spare fridge for extra garden produce is a 24v fridge made by sunfrost, it's still one of the most efficient fridges you can buy and it's 23 years old and I think the wires going to it are either 6 or 8 gauge wire, copper the size of a pencil! and it's a short run of wire.
The low voltage wiring in the rest of their house isn't really used, I put it in for LED lighting because you can get 12v and 24v LEDs for boats and RV's, but that extra wiring is not something I would bother doing again, with switching power supplies you loose such a small amount of energy that it just makes sense to bump the voltage up for going long distances, so while I am sure someone could make or hack more devices to run straight off the lower voltage from an off grid system I don't see it as being worth while.