This question has been on my mind for years. WHY are certain gases (R12, R134A and recently R1234YF) always used for car AC and another(R22 and R410A) always used for home AC? To me it would seem that the refrigerant that works well in a car AC would work well in a window or central AC unit also, or vise versa. They have the same basic goals: Keep your car or house at about 65-75 degrees while using as little energy as possible and being as environmentally friendly as possible, while still preferably being non flammable, running at reasonable pressures and being non toxic. Is that logic not accurate? I think that the reason the refrigerant for a car AC and home AC is different is so you have to buy and stock more types than really necessary, making the big chemical companies very wealthy. I think that almost all AC systems have WAY more in common than not. Any input is very much appreciated! Thanks!