This study considers the technical potential concerning the energy efficiency attainable for vehicles with alternative powertrains within 10-20 years. The potential for electric vehicles (BEVs), hybrid electric vehicles (HEVs) and fuel-cell electric vehicles (FCEVs) is assessed and compared with the potential improvement in conventional vehicles with internal combustion engines (ICEVs). Primary energy efficiency is the measure used in this study for comparison. The calculations of primary energy efficiency are based on three different resources: fossil fuels, biomass, and primary electricity from wind, solar or hydropower. This study shows that there is potential for doubling the primary energy efficiency using alternative powertrains in vehicles such as BEVs, HEVs and FCEVs, compared with existing ICEVs. All vehicles with an alternative powertrain have a higher potential for primary energy efficiency than vehicles with an improved conventional powertrain. No "winner" amongst the alternative powertrains could be identified from a primary energy efficiency point of view.