Electric cars. Recharging on a domestic socket leads to up to 30% losses

The ADAC has measured the energy losses when recharging electric cars using a domestic socket (230 V) or via a home charging station (wallbox type). The results show that boxes are much more efficient, while wall outlets cause up to 30% loss.


Raphael Desrosiers

Published on

When recharging, not all the electricity goes into the battery. A more or less important part is lost.


As the winter promises to be tough on the energy front, the ADAC (the German automobile club) publishes the results of a study which comes at just the right time. The organization measured the electricity consumption of four electric cars on a household socket (230 V – 2.3 kW) and a home charging station (wallbox type – 11 kW). Why ? Because the electricity consumed during charging is not the one displayed on the dashboard. Energy is indeed “lost” during the transformation of alternating current from the network into direct current (mandatory step to avoid damaging the battery), but also in the supply of components that control the charging process in the car . Finally, the last significant element causing a loss of energy: the charging cable, especially if it is long.

Variable losses

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electric charging wallbox

According to the results of the ADAC, wallboxes or wall boxes are the best way to charge at home.


To quantify these losses, the ADAC compared the consumption indicated by the on-board computer with that effective from the electrical installation. The results vary more or less noticeably from one vehicle to another, but it is clear that wall sockets are the least efficient. Experts claim to have measured losses of up to 30%. Wall boxes are more efficient with losses contained between 5 and 10% in 11 kW. The loss increases significantly at reduced power.

Electric cars: losses when charging with alternating current

Wall box
power 11 kW/loss

Wall box
reduced power/loss

Renault Zoe 2,3 kW / 24,2 % 11 kW / 9,7 %
Volkswagen ID.3 2,3 kW / 13,6 % 11 kW / 9,0 % 5,5 kW / 9,2 %
Tesla Model 3 2,3 kW / 15,2 % 11 kW / 7,7 % 3,5 kW / 11,4 %
Fiat 500e 2,3 kW / 12,7 % 11 kW / 6,3 % 3,6 kW / 13,9 %

Source : ADAC

Charging on a more economical wall box

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ds3 crossback charge

The installation of a wall box is often offered when purchasing a plug-in vehicle.


Results which highlight a loss proportional to the charging time: for an equivalent charge, a wall socket will take longer than a box and will therefore supply its on-board charger and its electrical system which operates in the background for longer , resulting in more wasted energy. Recommendations to users of electric vehicles are therefore simple: favor installations that allow the car to be left plugged in for the shortest time. The savings generated by the reduction in losses could reach up to €120 per year, at the current cost of electricity (for a Renault Zoe which drives 10,000 km/year). The ADAC also encourages manufacturers to be more transparent about pressure drops, which are currently not communicated. On-board chargers should also be more efficient and the on-board system cut as much as possible.