The invention relates to a method and a control system for controlling an auxiliary device of a vehicle, wherein the auxiliary device is automatically started at a starting time which is determined based on an estimated departure time of the vehicle. In particular, the invention relates to an air-conditioning device which is automatically started for pre-air-conditioning (PAC) based on an estimate departure time of an electric or hybrid vehicle. The invention enables a precise and flexible automatic determination of an activation time of the auxiliary device, wherein determining a time of usage of at least one home appliance of a user of the vehicle; determining a departure time of the vehicle based on the time of usage of the at least one home appliance; and determining a starting time of said auxiliary device based on the determined departure time of the vehicle are determined.