I'd go with 12v until its not enough. You can always do a battery swap exchange between the house battery and a vehicle, or another battery at the house on a trickle charger. Just take it with you. Presto chango. Get heat from a propane reddy heater. Even motion detector lights have 12v versions. If you have a windy area nearby, get a small wind turbine charger to maintain the batteries. Deep cycle recomended.