However, this is not a hard and fast rule as it depends on a car’s physical size, engine power, engine technology, weight, etc. In general, the smaller the vehicle, the lower the fuel consumption.
However, when comparing WLTP efficiency figures for a range of EVs for sale in Australia, most large electric vehicles fall at or above 20 kWh/100 km. Smaller models are expected to reach consumption in the high teens. Using this as an average, it is reasonable to reason that anything below these numbers is considered efficient.
The reasons behind these variances include the load the vehicle is carrying, the type of driving performed, the level of brake regeneration, sustained speed, the number of passengers in the vehicle, and the ambient temperature of the atmosphere. It is well documented that electric vehicles are much less efficient in colder climates, especially when the car’s climate system is turned on to fight the outside elements.
As mentioned, there is no right answer to finding the perfect kWh/100km figure for an efficient EV, as there are currently too many differences between EV powertrains, dimensions, weights and specifications, and driving styles. However, the above economy figures should provide some insight into what each type of electric vehicle should be using in terms of energy consumption at this early stage.