In order to develop various parts and components for hybrid electric vehicles, understanding the effect of their structure and thermal performance on their fuel consumption and cruising distance is essential. However, this essential information is generally not available to suppliers of vehicle parts and components. In this report, following a previous study of electric vehicles, a simple method is proposed as the first step to estimate the algorithm of the energy transmission and then the cruising performance for hybrid electric vehicles. The proposed method estimates the cruising performance using only the published information given to suppliers, who, in general, are not supplied with more detailed information. Further, an actual case study demonstrating application of the proposed method is also discussed. In the case study, the effects of glass and body heat transfer characteristics on fuel consumption are calculated for a hybrid electric vehicle with a positive temperature coefficient (PTC) heater installed for use during winter in cold regions. In addition, an anti-fog control method is modeled as a countermeasure against declining cruising distance. In this case, it is assumed that the relative humidity around the front windshield is detected and the recirculation ratio of the ventilation subsequently controlled in order to maintain defogging. The effect of the anti-fog control system combined with the thermal insulation efficiency of the glass on cruising performance is also examined along with the fuel consumption estimation method. The results obtained indicate that improving the thermal properties of the glass does not have a significant effect without the anti-fog control system. Hence, anti-fog control enhances the improvement effect of the thermal properties of the glass on fuel consumption.