Two aspects should be included when discussing the efficiency of electric vehicles, to avoid long-term aberrations, rebound effects and the excessive load of electricity grids:
Let's first focus on the efficiency of individual BEV. The heavier the vehicle in relation to the object moved around, the more specific energy is required for propulsion. The announced luxury class automobiles , some of them already available, E-PKW der Oberklasse warten einerseits mit fest verbauten Akku-Kapazitäten von 95 Kilowattstunden, andererseits mit Leergewichten von über 2,5 Tonnen auf. For comparison: The old VW Beetle, just as the Smart, aber auch der Smart wiegen 730 Kilogramm. In practice, the consequences are experienced by the driver. Despite the impressive availably held capacity, ist der Akku bei einer Fahrt über die Autobahn bei Richtgeschwindigkeit nach rund 300 Kilometern entladen. Vermutlich werden aber auch zukünftig durchschnittlich nicht mehr als 1,1 Personen oder 100 Kilogramm mit einem solchen Fahrzeug transportiert. If the maximum range is not needed, because only short distances beeing covered in daily use, the weight of the battery and the additional weight of the BEV due to its construction respectively, counter an efficient use .
The second aspect zooms out to fleet efficiency. Should the trend for urban car sharing continue, small vehicles are likely to be favoured, while long ranges, due to their construction, are less obtainable. Thus loading pauses at day time will occur. The result is longer downtimes within a fleet and a surplus of vehicles, in order to meet the demand for individual mobility. This becomes even more apparent, once the vision of fully autonomous BEV fleets becomes reality. The shorter the dead times of the individual BEV, the smaller can the size of the fleet be kept.
Exchangeable battery act against these negative effects. If after three minutes of battery replacement – regardless of the energy density of the battery – full range is again available, light BEV with smaller (lighter) Batteries will be interesting for individual customers. Not until the units of a BEV fleet become permanently available due to rapid battery exchange, will we find out, how small the (autonomous) fleet may actually be in urban areas.