by bjdmytro on Sun Feb 25, 2018 12:20 am
I've lived in an off the grid cabin for four years (though not currently) and tried to figure out this very thing. Eventually I got the solar power system working to a higher level, but I still could not find an adequate heater for my uses, I hoped for a DC heater that could maintain the 90F, but couldn't find anything like that.
I now have a 1000 watt solar array and a midnight solar classic charge controller, with its relay controlling the inverter, when I'm away. However, the heating pad and thermostat needed for growing koji could easily be handled by this setup, so long as there is not a cloudy spell, the ambient temperate of the room isn't too cold, it is not right around the winter solstice, and I don't expect to have strong electricity usage early in the morning, otherwise the drain would be too heavy on the battery array.
There is an alternative that I've not tried. Some sources recommend to work with an insulated box (a cooler) and several times a day replace pans/bottles of hot water in it to maintain temperature and humidity. I have never tried this method, I use a heating pad and thermostat with a pine koji box in a cooler for my koji growing currently, in an on-the-grid house. This system consumes less than a kilowatt hour during the darkness of night, if the room is relatively warm. If you have a wood burning stove you could warm up water and experiment with this alternative. Otherwise the solar setup that I mentioned cost a couple of thousand to install and I did it all by myself. To hire someone would probably double the price.