Germany lags behind in bidirectional charging
Mercedes-Benz announced the introduction of a fully integrated service offering for bidirectional charging at the IAA Mobility 2025.
Mercedes-Benz
More and more cars are ready for bidirectional charging, vehicle-to-grid is slowly gaining momentum. But here, many factors act as a brake. Why does this need to change and will it? A look at neighbouring countries offers a jump start.
It has slowly become known: Green energy is cheap, but storing it is expensive - yet necessary to stabilise power grids and bridge periods of low renewable energy production. Electric cars could store excess electricity from the home photovoltaic system during the day and release it again in the evening, for example to run the washing machine. Experts refer to this as Vehicle-to-Home (V2H). So why put an expensive electricity storage unit in the basement when the car in front of the door has a battery?
On a larger scale, electric cars represent a huge electricity storage system that could be distributed across the country, which would significantly relieve transmission networks. "Therefore, Vehicle-to-Grid, or V2G for short, i.e., the transfer of electricity from the electric car to the public distribution network, is considered essential for the success of the energy transition," explains Götz Warnke, chairman of the Sustainable Mobility Committee of the German Society for Solar Energy (DGS). However, there is little to see of this in Germany. "Despite the fundamental recognition of the necessity and the approval of important stakeholders, V2G is progressing at a snail's pace," complains Warnke.
The prerequisites for bidirectional charging
The 'vehicle-to-grid technology' is anything but new. The idea has been pursued since the early 1990s and tested since the early 2000s. The necessary bidirectional charging process is not rocket science. With bidirectional charging, electricity can flow in two directions: from the grid into the storage and back out again, back into the grid. The peculiarity of the electric car battery is that it operates with direct current, while alternating current is used in households, which is why the alternating current must be converted into direct current (DC) during charging. This is done by a rectifier, either in the vehicle's onboard charger or in a DC wallbox, which intelligently controls the charging and discharging process to meet the needs of the power grid.
It becomes more challenging when an armada of cars is supposed to feed excess electricity into the public grid, becoming part of a virtual power plant. It requires a charging infrastructure, both hardware and software, capable of supporting V2G functions as well as interfaces that enable data exchange between vehicles, charging infrastructure, and the power grid. This also requires uniform standards and rules to ensure connectivity between various vehicle models, charging infrastructures, and the power grid. Moreover, a home energy management system (HEMS) is needed to predict, for example, how far a vehicle can be discharged to remain ready for use.
France shows how it's done
Everything is feasible, as a look at Finland, the Netherlands, or France shows. Across the Rhine, the Renault Group, Mobilize, and The Mobility House are already operating a vehicle-to-grid. Renault 5, R4, and Mégane drivers have been able to charge and drive for free since last year - provided they have a corresponding bidirectional 11-kW AC charging station along with the associated energy contract. The first users earn 600 euros per year with bidirectional charging, according to the provider, making annual mileage under 10,000 kilometres practically free. 'With the launch in France, we have reached a significant milestone that proves we are technically capable of successfully implementing V2G,' says Thomas Raffeiner, founder and CEO of The Mobility House, 'Now it is important to show in Germany that electric cars can be driven for free and emission-free.'
But that might take a little longer. It's not due to rolling storage. More and more vehicles are capable of or prepared for bidirectional charging. These include models from BMW, BYD, Cupra, Genesis, Mercedes-Benz, Nissan, Volkswagen, or Volvo. The first bidirectional wall boxes are also available in Germany. 'In Germany, around 1.65 million battery-electric vehicles are already registered - with a combined storage capacity of over 100 GWh, more than twice as much as all pumped storage power plants in the country,' says The Mobility House. 'Technically, we are on the way: according to TÜV, at least 166,000 vehicles could already charge bidirectionally. But there are still issues with regulation and generally with all the cogs meshing together.'
The reasons for Germany's lag
Above all, the eternal tragedy of 'smart meters' is a significant hurdle to advancing the topic. 'Currently, only about two percent of German households have smart meters, while in Bulgaria it's 80 percent and in Denmark even 100 percent,' says Warnke. But without intelligent load management, it won't work.
Furthermore, house connections and wall boxes must be able to handle the technical differences of various electric cars (such as the size of the battery or the on-board voltage) to avoid short circuits or damage to the battery. Who is liable if something goes wrong? This leads to the unresolved question of how OEMs will design warranty services for car batteries when they are charged and discharged more frequently than usual due to bidirectional charging. The ADAC also sees the legislator as having a duty, because electric cars are legally cars and not battery storage, for which there are sometimes more favourable legal requirements. The transport club is therefore advocating for tax equality between stationary and 'rolling' storage. Otherwise, there is a risk of double taxation of electricity - when refuelling and when feeding back into the grid. And: How attractive can billing with the electricity supplier be made for the electricity supplied, so that the investment in significantly more expensive wall boxes and cars is worthwhile at all?
Conclusion: Technically, Warnke sees no problems, especially since other countries have shown how it is done: "The main hurdles in Germany are primarily the ridiculously slow smart meter rollout, the snail-paced standardisation practice, including that of the VDE, and probably also fears of the tax authorities that funds could bypass them." Much depends on politics. "However the decisions are made there: We need storage for the stabilisation of the energy system," says Warnke. And the expansion of such storage is more sensible than the construction of new gas power plants.
This article was first published
at all-electronics.de
