A 12-volt RV air conditioner runs straight off your house battery, so you can sleep cool at a trailhead with no generator, no shore power and no inverter losses. That is why 12V DC units took over van builds: a 120V rooftop unit needs an inverter and a very large bank to survive a hot night.

Two mounting styles are here. Rooftop units drop into a standard 14x14 vent opening and are the simplest install. Back-pack and mini-split units mount on the rear doors or inside a cabinet, keeping the roof free for solar and a rack. Heat-pump models add reverse-cycle heating, which covers shoulder-season nights without burning any fuel.

Size the battery bank before you buy - see RV Power Kits & Batteries - and insulate the shell first with van insulation, which buys more cabin comfort per dollar than any compressor.