I have a short bus
and I plan on driving with 7 to 10 people on hot 105 f (40C) days, and a few winter days, at or below freezing. I am installing a dash mount a/c, heater system for the driver, front windows, and shotgun passenger. I will have at least one, or two heaters in the rear, and a ceiling mount a/c in the rear for the passengers. The ac system should total about 30k to 35k btu and run from one compressor and about 50" (1.3m) of condenser mounted at the skirt. Only the heaters will work without the engine running. The number of btu needed come from charts of companies that install a/c in buses, and are figured on a ten person load at 105f (40c) Takes about 30 minutes to cool a bus at 125f (52C) to 78f (26C) with ten on board an 105f (40C) according to charts.