Every vehicle has to use some source of energy to advance. The source of energy can be fuel, a battery, a fuel cell, food for a cyclist and the earth’s gravity when falling downwards.
This primary energy then has to be transformed into mechanical energy and this is the role of the motor. Today we have internal combustion engines (ICE) and electric motors (let’s leave aside the cyclist’s muscles). During this energy transformation there is energy loss and it often takes the form of heat loss.
When comparing vehicles one of the first criteria is engine efficiency (or more exactly that of the powertrain and the differential) which is the ratio between the energy available at the wheel and the energy provided by the source. But any comparison between ICE, electric and hybrid motorizations only becomes meaningful when considering the full Life Cycle Assessment (LCA) from well-to-wheel.
Other comparative criteria include the forces of resistance which hinder a vehicle’s forward motion: aerodynamic drag, vehicle weight when accelerating or going uphill and tire rolling resistance resulting from their indispensable deformation.
Lastly for any given vehicle, energy consumption closely depends on the conditions of use: sporty driving, or eco-driving, normal driving in congested traffic with numerous stops and starts: traffic flow. Connected driving is another way of saving energy … and keeping one’s cool!
Food for thought on consumption: when a 1.5 metric ton automobile consumes on average 8 l / 100 km to transport 4 people and their luggage, a loaded 40 metric ton truck consumes 35 l / 100 km to transport a load of 24 metric tons.