Testing in Germany has shown car owners could be losing up to 24.2 per cent of the power they’re paying for when they charge their EV at home, but using a wall box reduces the wastage drastically.

The ADAC motoring club used five EV models to study the effectiveness of three home-charging methods: a standard home power point at 2.3kW, a wall box at outputs of 11kW and 22kW, and a wall box at 4.1kW, which was used to mimic charging using surplus power from solar panels.

EV home charger
4

Results of the testing are especially useful for Aussie drivers because our standard residential electricity supply matches Germany’s at 230 volts on single-phase supply, and 400 volts on three-phase supply. The models used in the study were the Tesla Model Y, Mercedes CLA 350 EQ, Volkswagen ID.7, Renault R5 E-Tech and Volvo EX30. All were charged from between 10 and 90 per cent.  

Charging the Mercedes from the power point without a wall box resulted in a wastage of 24.2 per cent, with that figure falling to 13.7 per cent for the Renault, 12.7 per cent for the Tesla, 14.2 per cent for the Volvo and 15.3 per cent for the VW. The ADAC put the high result for the Merc down to its onboard charger, which draws juice at eight amperes. 

Using a wall box at 11kW showed a marked improvement: the Mercedes came in at 6.9 per cent of power wasted, with the Renault at 5.1 per cent, Tesla at 6.1 per cent, Volvo at 7.0 per cent and Volkswagen at 6.9 per cent. Solar charging produced waste of 12.8 per cent for the Merc, 8.0 per cent for the Renault, 9.4 per cent for the Tesla, 9.1 per cent for the Volvo and 10.6 per cent for the ID.7.

Losses from using a wall box are roughly half what is wasted through power-point charging alone, and the ADAC noted the impact of waste incurred from solar is softened because the power is basically free. The advantages of using a wall box are stark, with the efficiency savings effectively paying off the cost of the equipment. As WhichCar noted in a previous story, installing a 7kW AC wall box can guarantee a full charge overnight for most models.