The all-electric REVO ®-E rooftop unit for hybrid, electric, and trolley buses is characterised in particular by intelligent energy management, i.e. demand-oriented production of cool air depending on the available energy, and special compressor integration. The extremely compact electric compressor is located on the roof and not, as hitherto, at the rear of the vehicle. This has obvious advantages and due to the integration of all refrigerant-conducting components the closed system is more efficient, leak-proof and virtually maintenance-free.