The main design criteria for the modern sustainable development of vehicle powertrains are the high energy efficiency of the conversion system, the competitive cost and the lowest possible environmental impacts. The need for efficiency improvement of the vehicle energy system induces the search for an innovative methodology during the design process. In this article the energy services for mobility and comfort are integrated. The energy integration of the mobility and the comfort service is applied through an innovative methodology combining process integration techniques. The methodology is applied on the energy integration study of a hybrid electric vehicle powertrain with the vehicle cabin. The energy balance of the internal combustion engine is done and discussed, according to the operating points. The energy requirement for comfort in the cabin is also determined, according to the seasonal requirement for heating or cooling. Work cycles for heat recovery are described and investigated. The minimum energy requirement is determined for different mobility and comfort situations. The energy recovery potential of a single stage Rankine cycle for a diesel engine in combination with a hybrid electric powertrain is assessed. The Rankine cycle circuit and equipment are simultaneously presided.