how much power does a bus air conditioner need to operates?

Answer 1

Rooftop airconditioners for RVs are typically 1 to 2 horsepower, and sometimes you need 2 of them to effectively cool the volume of a larger RV. Busses are even larger (more volume) than a 25' RV, so as a first-order approximation I would say a minimum of 5 horsepower.

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