Bidirectional charging

Electric cars as electricity storage: enormous savings potential

The extensive use of e-cars as electricity storage systems could reduce the need for investment in the European energy grid by more than 100 billion euros between 2030 and 2040.

(Bild: APA/dpa/Arne Dedert)

According to a study, using electric cars to store electricity could reduce the costs of the energy system across the EU by up to 22 billion euros a year. And consumers could also make significant savings.

With bidirectional charging, vehicles take surplus and therefore cheaper solar and wind power from the grid during the day and feed it back into the grid in the evening or at night. The Fraunhofer Institutes for Solar Energy Systems and for Systems and Innovation Research have calculated the cost benefits that this bidirectional charging could bring for grid operators and consumers on behalf of the EU interest group Transport & Environment.

According to the study, the extensive use of e-cars as electricity storage systems in the most advantageous scenario would reduce the need for investment in the European energy grid by more than 100 billion euros between 2030 and 2040. However, this would require around half of all e-cars and battery-powered trucks to be able to feed the electricity back into the grid by 2030. If this flows directly into the overall grid, it is referred to as vehicle to grid (v2g, i.e. from the car to the grid).

Using the car battery for your own household
Owners also have the option of using the electricity stored in the car battery for their own household (vehicle to home, or v2h), particularly in the case of single-family homes. The electric car could then become an energy supplier in the particularly electricity-intensive evening hours, for example, and reduce electricity costs. It would then recharge at night when demand is low and electricity is cheap.

In Germany, the authors of the study calculated that a four-person household could save more than 700 euros a year in this way. If the electricity is fed into the overall grid, there would also be any additional payments for car owners.

Obstacles due to inconsistent standards
However, there are a number of obstacles to the widespread use of bidirectional technology. Firstly, there is the problem of electricity conversion. The alternating current available in the grid has to be converted into direct current when charging electric cars and vice versa. For some models, this is done in the car. For others, this requires a more expensive wallbox to which the car is connected. The authors of the study recommend a uniform standard that manufacturers can adapt to.

Lack of political framework conditions
According to the study, there is also a lack of regulatory and political framework conditions to make the current niche technology marketable on a large scale. At an industry meeting a few days ago, German Economics Minister Robert Habeck (Greens) held out the prospect that bidirectional vehicles and services could be commercially available from 2025.

"As mobile electricity storage units, electric cars can make a huge contribution to stabilizing the electricity system," Habeck said. "Their batteries can be used for intermediate storage of electrical energy and thus create additional flexibility."