A waste energy-based vehicle air conditioning system includes efficient compression driving means coupled to refrigeration means, which greatly reduces the extra fuel otherwise required to operate conventional vehicle air conditioning systems. In one implementation, the compression driving means includes a controller (e.g., magnetic clutch) that couples mechanical waste energy from an engine fan axle, a vehicle drive shaft, or a transmission shaft directly to an axle of a refrigerant compressor. Alternatively, the controller can also include a battery that is charged from the mechanical waste energy. Upon detecting the presence of vehicle waste energy, such as the driver's foot releasing from a gas pedal, the controller powers the refrigerant compressor with a rotating axle (e.g., during deceleration) or with the vehicle's battery power, as appropriate. One or more kits can be used to retrofit existing vehicles to operate the respective air conditioning systems principally on waste energy.