The Future of Bidirectional Charging – Insights From Mercedes-Benz

Interview with Frank Spennemann, Senior Manager Charging Solutions Energy of Mercedes-Benz

AC or DC – Which technology will prevail?

Dr. Frank Spennemann (Mercedes-Benz Mobility AG): This question will likely be answered in the next 5 to 10 years. Currently, we see both AC and DC bidirectional charging. Around 80% of manufacturers start with DC because it has certain technical advantages. It’s more easy to connect it with the grid. If you feed the grid you have to comply with so called grid codes, which are defined by the grid operator.

With DC, the wallbox ensures grid compliance. With AC, compliance is split between the car and the wallbox, making it more complex. Some countries are still defining how AC bidirectional charging should work. My gut feeling is that we will see more DC solutions in the beginning.

How does Mercedes-Benz plan to integrate bidirectional charging in vehicle fleet?

Mercedes-Benz has already been offering bidirectional-capable cars in Japan for several years because there is a clear standard (CHAdeMO). All EQ models (EQE, EQS, EQB, EQA) in Japan support bidirectional charging.

We believe interoperability is key, meaning that bidirectional charging must be based on a standard. The relevant standard is ISO 15118-20, released about 1.5 years ago. All OEMs and wallbox manufacturers are working on implementation, and we are doing the same. Our next generation of EVs will be bidirectional-capable.

How long does it take until we actually see it integrated in fleets in Europe in a greater number?

As mentioned we intend to introduce it with the next generations of our vehicles and you will see when they hit the market.

What specific added value would you like to offer Mercedes- Benz customers through the bidirectional charging?

As a car manufacturer we have the bidirectional capability of the vehicle. Of course we do this because we see the tremendous value:
1. Energy Independence & Backup Power:

• In markets with frequent power outages (e.g., the US), a car can serve as an emergency power source. A typical European household consumes about 10 kWh per day. An EQS with a 110 kWh battery can power a standard home for more than a week during an outage.
• People with photovoltaic (PV) systems prefer to use their own solar energy. A bidirectional car, ideally combined with a small home storage system, can extend this capability. It allows homeowners to store nearly all of their solar energy and feed it back into their home – especially useful for powering a heat pump or air conditioning.

2. Financial Benefits of V2G:

• EVs can be integrated into the whole energy grid, which is in desperate need of flexibility – and flexibility is financially rewarded.
• Germany’s total peak power load is around 70–80 GW. If 7 million cars are connected at 11 kW each, that equals 15% of the total passenger car fleet.
• Customers could earn €400–700 per year, depending on their car, behavior, and other factors.

3. Supporting the Energy Transition:

• Research simulations show that bidirectional cars are essential for grid stabilization and transitioning to renewable energy sources.

What are the barriers to widespread adoption?

The main topic is, that we have to have a product which the costumer is willing to take. Therefore you have to have the financial benefit.
Regulatory Challenges: In Germany, there is a so-called double taxation issue—when energy is stored in the car and later fed back into the grid, customers are taxed twice. This eliminates the financial incentive and must be addressed.

The topic will also be a key focus at the upcoming Power2Drive Europe 2025 exhibition with the Special Exhibit Bidirectional Charging.

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