The closed cabin temperature is anticipated to be cooled down when it is a bit hot inside the driving car. The traditional air-condition lowers the cabin temperature by frequently switching the status of the compressor, which increases the engine’s parasitic power and shortens the compressor’s service-life. The semiconductor auxiliary cooling system with the properties of no moving parts, high control precision and quick response has the potential to assist the on-board air-condition in modulating the cabin temperature with relative small ranges. Little temperature differences between the cabin and the outside environment means that the system energy consumption to ensure the occupant comfort is relatively low and the inefficiency could be made up by the renewable energy source. This research focuses on the influence of the vehicle speed and the ambient temperature over the cooling energy consumption considering occupant heat dissipation in order to maximize the system energy utilization. Firstly, the occupant heat dissipation model is established and the system refrigerating capacity is confirmed for occupant comfort. Secondly, the temperature and the heat flux density at both ends of the semiconductor are studied. Finally, the energy consumption regulations of the auxiliary cooling system are clarified for different vehicle speeds and ambient temperatures. The results show that the vehicle speed is a key factor affecting the supplied current, especially for the vehicle speed less than 40km/h. The system current variation is within 0.4A corresponding to the ambient temperature changes. The occupant heat dissipation changes the current range. The system energy utilization could be improved by controlling the supplied current in a relatively small range at various vehicle speeds and ambient temperatures.