Try to eliminate the inverter as much as possible. Use automotive lighting and fans, a trip to an auto parts store or junk yard or ebay you can pick up some very nice 12v lights. Same with fans, those little ones that mount neat the window on a bus or large truck or the hvac blower motor. Stick with common parts like the motors for the fan from a chevy truck so there are enough to be plentiful and keep the price down.
Most consumer inveters are under 80% efficient so they waste a lot of energy.