2. Energy and power density

2.4. Efficiency

Electric car efficiency vs. cars with internal combustion engine

The energy density of current electric vehicle batteries is many times lower than the energy density of fossil fuels. Thus, an electric car has less energy available than a car with an internal combustion engine. On the other hand, the electric drive achieves much higher efficiency (up to 96%) than the drive with an internal combustion engine (max. 42% diesel, 35% petrol).

Overall efficiency in operation

  • Efficiency of a car with an internal combustion engine: 20%
  • Electric car efficiency: 85% (without charging)
Oxygen

Oxygen used in combustion is a key factor causing a critical difference in the energy density of traction batteries and fossil fuels. While the electric drive uses only the energy stored in the battery, the function of internal combustion engines is based on atmospheric oxygen.

  • Oxygen consumption: a car with a fuel consumption of 7 l/100 km consumes about 122 liters of O2 per 100 km.
The promising technologies of LiO2 batteries using external oxygen then reach energy densities comparable to fossil fuels.