I have been trying to learn how home air conditioners work since I had some problems yesterday with my split system. I was reading here: http://www.energyquest.ca.gov/how_it_works/air_conditioner.html This is a stupid question and basic mechanical engineering, but there is something about the process that seems counter-intuitive to me. I understand that the evaporation part is essential to removing heat from your house. But when compressing the refrigerant, you are adding heat into the system which has to be removed anyway in the condenser. My question is; must the gas be compressed in order for it to condense into a liquid so that the evaporation can occur? Or is this just a necessary part of the pumping part of the process?