Unfortunately it does draw anywhere from 4 to 8 hp to run an A/C unit with sufficient power to cool a cab that is mostly glass. If you have a hydro unit, many people say that takes away a certain percentage of power as well. So, if you were to add a cab with A/C to a 20 hp tractor, you'd end up with about a 10 hp tractor. Now try to move around and do any sort of real work at all with a 10 hp tractor that weighs 2500 to 3000 pounds or more, and you'd have one useless tractor. That is basically the thought process of why the manufacturers are not going to offer A/C in a 20 hp tractor. If it were a gear drive tractor, and weighed about 1500 pounds max, you may be able to use a 48" mower with it if the grass wasn't too high.