Air conditioners work on basically the same principle as the cooling units of kitchen refrigerators. Their cooling efficiency is way higher though. In either system a refrigerant extracts heat from the space to be cooled and dissipates it to the outside. An RV air conditioner should additionally reduce the humidity.
Evaporation systems: Water is vapourised in a roof-mounted unit and collected in a filter. A fan draws ambient air in through the filter, which results in a heat exchange. Benefits: low current consumption, lightweight. Drawback: The energy efficiency depends on the ambient humidity; so the performance of the system varies. It drops when the humidity is > 85% – and that’s exactly the level where air conditioning is needed. Moreover, evaporation systems will, by nature increase the humidity in the vehicle, regardless of the ambient conditions.
Compressor systems: A gaseous refrigerant contained in a closed circuit is pressurised and turned into liquid. The liquid then flows through a pipe system and turns into gas again in the evaporator. In the process it extracts heat from the surrounding environment; the outside of the evaporator cools down. The refrigerant then flows back to the compressor, where the cycle begins again. In this way the air conditioning system dissipates air and cools the vehicle interior. Additionally, it circulates and dehumidifies the room air. Benefits: consistent, powerful cooling performance, largely independent of the ambient temperature and humidity. Many compressor air conditioners integrate a heating system. The performance and efficiency of such heating systems depend on what type you have. If you have a simple heating resistor the performance will certainly be adequate for a chilly evening.
RV Air conditioners with energy-efficient heat pump technology provide a heating capacity of 3000 watts or more – enough to get the vehicle warm in the early or late seasons.