Further when the air runs for hours at a time the energy consumption goes up. It may be important to watch the voltage.
The 13500 btu unit in my class C starts out at about 1200 watts--but I have seen over 1900, too.
If I've been driving for a couple of hours the roof air takes a long long time to cycle. The heat from the engine and transmission radiate up through the floor. The engine weighs about 640 pounds and if it is at 200 F then it has a heat content of about 9000 btu's (assuming I get it to 80 f). The transmission weighs a further 275 pounds.
I finally have an autoformer and I'd recommend one in a flash. The unit I purchased goes into boost mode immediately when the roof air starts. Then after the compressor is up to speed it drops out.
