How energy efficient are e-vehicles?
The best way to assess the efficiency of propulsion systems is engine efficiency, which states how large a percentage of the primary energy is transformed into motion. The engine efficiency of a spark ignition engine is just 22 percent, in other words, more than three quarters of the energy contained in the fuel is not used for propulsion but rather lost as waste heat. If you further consider the energy losses associated with making the fuel available, the average amount of the initial energy that is actually used to move the vehicle drops to less than 20 percent. An electric motor on the other hand has an engine efficiency of about 79 percent, making it highly efficient. And even if you consider the losses associated with transporting the electricity and with charging the battery, 64 percent of the primary energy (in this case electricity from renewable sources) can still be converted into motion. This makes an electric car three times more efficient than one with a conventional combustion engine.