A joint study by public research university RWTH Aachen and The Mobility House Energy, a German technology company specializing in smart charging solutions and energy management for electric vehicles (EVs), confirms there is only a negligible impact of Vehicle-to-Grid (V2G) bidirectional charging on batteries.

The researchers emphasize that there is still much discussion about the durability and performance of electric car batteries. However, several real-life examples and studies show EV batteries, when charged intelligently, degrade far less than initially perceived. Question is: what happens when you add even more charging cycles when using your car for V2G?

Renault is currently one of the most visible commercial providers of V2G in Europe, through Mobilize Power Solutions & The Mobility House. It introduced commercial V2G services in France from the end of 2023/2024, with plans for rollout in the UK in 2025 and later in Germany.

Benefit of up to €10,000 in ten years

The results of the German study show primarily that smart charging (V1G) significantly improves battery aging and increases range, and bidirectional charging (V2G) has only a minimal impact on overall aging and provides EV drivers with a possible benefit of over €6,000 to €10,000 over ten years. However, the methods used still raise additional questions.

In a lab environment, the researchers simulated over ten years using 11 kW AC charging, similar to home charging on a wallbox, and empirical ageing models (aging over time and aging caused by charging and discharging cycles).

They tested three charging strategies on various EV cell types (cylindrical, pouch, prismatic): immediate charging (IC), smart charging (V1G), and bi-directional charging (V2G). Those cell types are typically found in EVs from BMW, Tesla, or Lucid (cylindrical), VW, Nissan, Ford, or GM (pouch), or BYD, NIO (prismatic).

Plugging in at home at 11kW

Plugging in your car when coming home and starting to charge at the full 11 kW power to have your EV battery replenished as soon as possible to 100% is called ‘Immediate Charging’ (IC). There is no load balancing, and it happens regardless of the time of day, grid status (peak hour or not), and corresponding electricity prices.

According to the RWTH Aachen & Mobility House study, it aged the battery the most, around 18% in ten years, and gave no economic benefit compared to V1G or V2G. Theoretically, if your battery used to provide 400 km of range when new, that would be 328 km after ten years.

With ‘Smart charging’ (V1G), your EV charges one-way from the grid to the car, but intelligently, using a schedule, meaning charging when electricity is cheapest (e.g., at night) and pausing during grid congestion.

V1G best practice

V1G  turned out to be the best practice, reducing battery degradation and offering modest earnings. The report states that after 10 years, V1G leads to a reduction in battery aging of between 3.3 and 6.8 percentage points, or a loss of only 12% in capacity.

This corresponds to losing 1.8 to 3.6 kWh of battery capacity, which would theoretically translate to keeping 10.9 to 22.5 km of (WLTP) range more after 10 years, compared to immediate charging. And it can save you €2,000 to €4,000 over ten years by charging when prices are low.

V2G best financial benefit

Bidirectional charging allows an electric vehicle not only to draw energy but also to feed stored energy back into the public grid via the charging station. Vehicle-to-Grid (V2G) is an advanced form of this.

Energy from the EV battery is not only returned to the grid but can actively participate in the energy market, which allows you to earn money by selling your surplus electricity back to the grid operator when demand is high. But it puts more stress on the battery as the number of charging and discharging cycles increases.

After 10 years, the additional aging caused by V2G ranges between 1.7 and 5.8 percentage points. This corresponds to a capacity loss of 0.9 to 3.1 kWh, or 5.8 to 19.2 km of range according to WLTP standards.

Although degrading faster than with IC, that’s a minor impact, costing theoretically some €100 to €300, according to the researchers, but it is compensated by a financial benefit of €6,000 to  €10,000 to the customer over ten years, when selling his energy back to the grid.

Some questions remain

However, some additional questions remain about the methods used for this study. The tests were conducted on a cell level in a lab, not on complete EV battery packs or real cars.

This could make a difference when compared with real-world EV driving data or considering the actual battery management systems used in production cars. So it doesn’t account for thermal management, battery management systems (BMS), or temperature variability in real-world use.

There is no mention of the type of battery used in the test: NMC or LFP, for instance. This means the ageing results can’t be directly tied to any specific EV battery pack, limiting comparisons to theoretical vehicle model behavior.

Many modern EVs, especially higher-end models, use NMC (Nickel-Manganese-Cobalt) cells, which generally age faster and are more sensitive to deep cycles. Lower-cost EVs (e.g., BYD, VW ID family, Renault 5, Tesla Standard Range) often use LFP (Lithium-Iron Phosphate) cells, known for high cycle-life and better tolerance to repeated cycling, which would be ideal for V2G use.

Real EVs commonly include thermal control and software that discourages extreme SOC (state of charge) fluctuations like discharging completely or limiting charging to 80% in daily use, which helps moderate ageing impacts.

Real-world examples

On the other hand, recent real‑world examples and fleet data of electric vehicles have demonstrated longer‑than‑expected battery performance, often outperforming typical degradation projections. A Tesla Model 3, for instance, reached about 135,000 miles (~217,000 km) and still had 95% battery capacity, despite using NCA chemistry, which is usually more sensitive to degradation.

Fleet data for Hyundai/Kia EVs showed they still had approximately 99.3% capacity after 120,000 km, suggesting an annual degradation of <1%, well under general market expectations. A recent long-term test by Germany’s largest automobile club, ADAC, proved that a VW ID.3 retained 91% of battery capacity after 160,000 km.

Or a 2022 Mustang Mach‑E Premium RWD (Extended Range) in California, which still proved to have an EPA range of 290 miles (466 km) of the original 303 miles (487 km) when new, after driving some 230 miles daily and the odometer showing over 250,000 miles (402,000 km). It indicates only a 4% capacity loss, or some 96% remaining.