Bidirectional Charging: How V2H and V2G Work

Store surplus electricity from your PV system in your car and use it again in the evening? Charge your electric car at work and use the energy at home? Or buy inexpensive electricity on a dynamic tariff and feed it back into the grid later at a higher price? Sounds like a dream? This article explains what is behind it.

• What is bidirectional charging?

• How does bidirectional charging work?

• Can an electric car be used as battery storage?

• Preparing for bidirectional charging

• Conclusion

What is bidirectional charging?

With bidirectional charging, electricity does not flow in just one direction: your electric car’s battery can receive energy and release it again when required. This means you can use the vehicle battery not only for driving, but also to store surplus electricity on particularly sunny days or whenever your home cannot use all the available energy.

Bidirectional charging includes several approaches grouped under the term Vehicle-to-X (V2X), including the following:

• Vehicle-to-Load (V2L): Electricity is supplied directly to external devices at 230 V. You could use it to power a hair dryer or make fresh coffee, for example. An adapter is connected directly to the vehicle; no EV charger is required.

• Vehicle-to-Vehicle (V2V): Electricity flows from one vehicle to another, for example to resolve a range problem when no charging station is nearby.

• Vehicle-to-Home (V2H): Electricity flows from the vehicle into your home network, increasing your independence and reducing electricity costs. On average, a household uses around 7 kWh between 6 p.m. and 6 a.m., which most vehicle batteries can provide.

• Vehicle-to-Grid (V2G): Surplus electricity is fed into the public grid. This can support grid stability and help integrate renewable energy.

The last two forms only work if both the vehicle and the charging infrastructure—the EV charger—support bidirectional charging.

Since April 2022, ISO 15118-20 has defined communication standards for all of the technologies listed above. It is intended to ensure compatibility between bidirectional EV chargers, electric cars and energy management systems.

How does bidirectional charging work?

Several requirements must be met before bidirectional charging can work. First, a few basics for a better understanding:

The public electricity grid uses alternating current, abbreviated to AC. Electric-car batteries, however, use direct current, abbreviated to DC. To charge a vehicle, alternating current from the grid must first be converted into direct current for the battery. If energy is later fed back into the grid, it has to be converted again.

Converting electricity outside the vehicle (DC charging)

With DC charging, alternating current from the grid is converted into direct current inside the charging station before being supplied to the vehicle battery. To support bidirectional charging on the DC side, the charging station needs an inverter in addition to a rectifier.

DaheimLaden is currently developing a DC EV charger for home use and plans to launch it in 2027. For this reason, this article does not examine bidirectional DC charging in greater detail.

Converting electricity inside the vehicle (AC charging)

With AC charging, the vehicle converts the electricity itself. The onboard charger converts alternating current from the grid into direct current so the battery can be charged.

For bidirectional charging, this process must also work in reverse. Energy from the vehicle battery is converted back into alternating current and can flow into the home or public grid. The vehicle therefore requires additional technical components: an inverter and vehicle software that controls bidirectional energy flow through the AC onboard charger.

Bidirectional charging with an AC EV charger

More and more vehicle and charging-infrastructure manufacturers advertise bidirectional charging. In practice, however, the feature is currently often only available to a limited extent. The main obstacles are not technical feasibility, but regulatory conditions that are not yet fully defined, a lack of uniform communication standards and technical connection requirements from grid operators that remain unclear or incomplete in some cases.

For an EV charger to be described as “bidi-ready” or “prepared for bidirectional charging at hardware level”, it must meet specific technical requirements. These include a PLC module (Power Line Communication) for communication between the vehicle and charging station and support for standards such as ISO 15118.

The DaheimLader Business PRO already meets these requirements. However, given the current regulatory and market situation, there can be no guarantee that such systems will actually be enabled for bidirectional charging through a future software update. This depends in particular on approvals from vehicle manufacturers and grid operators and on further development of the legal framework.

Current market and regulatory situation

Important regulatory and technical foundations for bidirectional charging were established at the beginning of 2026.

An amendment to the German Energy Industry Act (EnWG) means that electric vehicles will increasingly be treated in a similar way to stationary battery storage. The aim is to make feeding energy back into the grid easier and more economically attractive, including through changes to the treatment of grid fees.

Further measures planned for the first half of 2026 are intended to enable more active market participation by electricity storage systems and charge points. In future, it should become easier both to optimise self-consumption and to feed energy into the grid in a controlled way.

A key requirement is an intelligent metering system (iMSys), which provides the legally required measurement and controllability. It has not yet been conclusively determined whether an additional second electricity meter will be required in practice; this may vary by grid operator.

The new technical connection rule VDE-AR-N 4105:2026-03 provides a concrete framework for practical solutions for the first time. Among other things, it defines standardised testing and certification procedures. The objective is for manufacturers to certify their systems centrally once and for grid operators to recognise that certification.

For AC coupling, the complete system must be certified, consisting of the vehicle, charging cable and EV charger. This is because the vehicle’s onboard charger actively participates in the conversion process and is therefore part of the overall system.

For DC coupling, certification is generally limited to the charging station itself because the vehicle technically functions solely as a battery storage system.

Important for customers: despite this progress, very few vehicle manufacturers currently support bidirectional AC charging in practice beyond the Vehicle-to-Load function. In particular, suitable vehicle software from the manufacturer is still missing. Even when the required hardware is present, this does not automatically mean that the function can already be used.

DaheimLaden’s conclusion

Although independent research occasionally presents a more optimistic view of bidirectional AC charging, in our assessment it is generally not yet practical for a conventional home connection.

The main reasons are unresolved regulatory questions, inconsistent requirements from grid operators, the currently high certification effort for the systems involved and missing vehicle-software components.

For the next two to three years, we therefore expect isolated, non-standardised solutions in specific local settings, typically as pilot projects. In these projects, grid operators, vehicle manufacturers and charging-infrastructure providers work closely together to achieve technically and legally compliant implementation.

From today’s perspective, widespread manufacturer-independent and standardised AC solutions are therefore not yet foreseeable.