Prius models that are equipped with tilt-slide moon roof have a remote control button on their smart keys for the remote air-conditioning system. Before leaving the vehicle, make sure the headlights are switched off or set to auto. All windows are closed and check the temperature setting of the AC system. As you return to the Prius, press the remote AC button on the smart key remote to activate the air conditioning system. The cabin will cool to the pre-set temperature without turning on the engine. The system will operate for 3 minutes. or until you open the door, whichever comes first.