It is well known that internal combustion engines only use a portion of the energy actually produced during combustion to drive the vehicle, with the rest lost as heat, friction, or other means. The TCS study now shows that electric vehicles are not free of losses during charging either, especially due to AC-to-DC conversion and battery storage. To measure these losses, 26 electric vehicles with less than 30,000 kilometres on the clock were tested, comparing the energy drawn from the grid with the energy actually extracted from the battery until it was completely discharged. This setup excluded wear-related influences from electronic components of the on-board charger or the high-voltage battery, ensuring representative results.
High Overall Efficiency
The overall efficiency is the ratio of energy drawn from the grid to the energy extracted from the battery until it is empty. The study shows an average overall efficiency of 89 percent, meaning 11 percent of the energy is lost throughout the charging process. The losses primarily occur due to the conversion of alternating current to direct current (around 7 percent), with additional losses from the battery's internal operation including thermal management (around 4 percent). The tests were conducted with an 11 kW (three-phase) output, the most widespread method for home charging, and at an ambient temperature of 23°C with a deviation of plus/minus 3°C.
Significant Variations
Among the 26 tested vehicles, noticeable differences in overall efficiency were observed, ranging from 84 percent for the lowest-performing vehicles to 93 percent for the most efficient ones. These losses have a financial impact on the users, making their quantification particularly important.
Range Loss Comes at a Cost
The study's estimates are based on an annual mileage of 15,000 kilometres or 30,000 kilometres every two years, the latter matching the service interval recommended by many car manufacturers. This value is also the standard used by TCS for calculating annual mileage costs over decades. Considering the overall efficiency during charging, ranging from 84 percent for the least efficient to 93 percent for the most efficient models, the charging losses create annual costs between 48 and 137 Swiss Francs, averaging about 80 Swiss Francs per year. Calculations are based on average costs of 29 Rappen per kWh, which corresponds to Elcom's Swiss median electricity price per kilowatt hour in 2025. Expressed as a distance, these losses range from 1087 to 2359 kilometres per year. Averaged across the 26 tested vehicles, this amounts to 1637 kilometres. While these figures may seem high, it is important to remember that the overall efficiency of electric vehicles in practice still far exceeds that of internal combustion engines.
Press
Contact:
Marco Wölfli, TCS Media Spokesperson
Tel. 058 827 34 03
marco.woelfli@tcs.ch
pressetcs.ch