The internal combustion engines are the most applied energy converters in the passenger cars. In order to increase their efficiency, energy integration techniques are used to recover the waste heat. An adapted methodology is required to design the Organic Rankine Cycle (ORC) as a waste heat recovery technology and to test the influence of the external temperature on its efficiency. The idea is to clusterize the external temperature profile on typical external temperature multi-periods. The energy system design is then tested on these typical multi-periods. In this article the methodology is applied on a vehicle with a small gasoline engine, in order to define the energy integrated configuration of the vehicle and to estimate the cost of the additional equipment. The performances indicators of the energy integration technology of the internal combustion engine is analysed and discussed, according to the multi-periods. The energy recovery potential of a single stage ORC for a small gasoline engine is assessed for different temperature profiles. The ORC equipment is simultaneously pre sized and its cost is estimated. The highest powertrain efficiency improvement due to the waste heat recovery for a small gasoline engine is estimated as 7%.