Vehicle-to-X – Vehicle to Load, Vehicle to Home, Vehicle to GridVehicle-to-X – Vehicle to Load, Vehicle to Home, Vehicle to Grid


Rarely has the world seen just how urgent the energy transition is as clearly as it does today – in terms of both climate protection and security of supply. After all, almost half of the electricity used in Germany now comes from renewable sources. The ruling parties have set a target of 80% to be achieved by 2030 in their coalition agreement. In mobility, too, there are now signs of a turnaround after a shaky start. One in four new cars sold in 2021 is electric – or hybrid, at the very least. More than 1 million electric cars are now up and running on Germany's roads and, according to the coalition agreement made by the three-way "traffic light" coalition (consisting of the Social Democratic, Free Democratic and Green Parties), there should be at least 15 million all-electric vehicles by 2030. But can wind and solar power, both fluctuating sources of energy, really provide us with a reliable electricity supply – especially since consumption is still on the rise due to electromobility, among other things?

Smart charging, V1G and Vehicle to Load – the opportunities that technology already offers

Vehicle to HomeVehicle to Home

In many cases, controlling vehicle charging is already a smart process even today. Especially if several vehicles are needing to be charged and you'd like to avoid costly expansion to the mains connection or pricey power peaks. Intelligent Charging and Energy Management systems like ChargePilot from The Mobility House accomplish this task. In a manufacturer-independent manner and based on open interfaces, the system enables average savings of around €250 per charging point and year. But such control is only internal or takes place downstream of the meter, so that only local conditions are taken into account.

In contrast, charging solutions that are beneficial to the grid (which are also often referred to as "V1G" solutions) have a communications link to the "outside". In a similar way to night storage heaters or heat pumps, they can respond to signals from energy suppliers when they offer time-of-use tariffs, for example. Distribution grid operators can also send signals to wallboxes to reduce charging power when the grid is overloaded. In this way, renewable energy in particular could be put to better use instead of being reduced (as is often the case nowadays with wind power), and grid expansion could be avoided. Since 2015, The Mobility House has implemented various examples of V1G smart charging with Renault, TenneT, the electricity supplier Bayernwerk and the municipal utilities company Stadtwerke München. But to fully exploit the potential, variable electricity and grid tariffs are needed, not to mention appropriately affordable metering and control.

Vehicle to Load (known as V2L for short) is a special case. Some vehicles already offer the option of directly powering electrical appliances using a special CCS adapter or built-in sockets. The load is usually limited to 3.6 kW, which is, however, perfectly adequate for all commonly used appliances.

Vehicle to Home – possibilities that are just around the corner

With Vehicle to Home (or V2H for short), the electric car becomes a stationary storage system for the home. The electric car is connected to the domestic power grid or the photovoltaic installation's inverter using a special wallbox downstream of the meter. So electricity generated at home can be temporarily stored in the vehicle battery and fed back into the household grid at a later time. Modern electric cars' battery capacities are already adequate to supply a household with electricity for several days, allowing users to optimize their private consumption without any need to invest in additional storage. What's more, the battery in the electric car doesn't need space in the household's connection compartment either. V2H is already a genuine opportunity nowadays in pilot projects (e.g. with E3/DC) and will also be feasible on a broad scale in the near future if the vehicle, charging station and PV installation meet the technical requirements. To begin with, this will only be an option for new installations since the systems have to be coordinated with one another.

Vehicle to HomeVehicle to Home

Vehicle to Grid – where we're heading

Vehicle to GridVehicle to Grid

If we take a closer look, we can see that storage is the solution to the renewable energy volatility problem. These storage solutions are already incorporated in electric cars. All you need to do is plug them in. On the one hand, electric vehicles that are stationary for a long time can make optimum use of green electricity, since, in most cases, charging is easy enough to shift to times when the sun or wind is strong. On the other, they can also store the renewable energy and feed it back into the grid when needed – when consumption is at a peak in the morning or evening, for example. Because the energy can flow in both directions, this technology also goes by the name "bidirectional charging". "Vehicle to Grid" (or V2G for short) is another commonly used term.

V2G charging is the only way to exploit the full potential of electromobility for the energy transition and grid stability. Decentralized, networked electric vehicles could therefore form a swarm storage system and strike a flexible balance with regard to wind and solar power as intermittent sources of energy. So, in the long term, they could also replace large natural gas-fired power plants, which have provided much of the flexibility to date.

V2G is becoming increasingly relevant to manufacturers of electric cars. The first few vehicles with this function are already on the market, and many have been announced for the coming months. V2G charging is already established in Japan. Innovative tech firms, energy suppliers and car-makers are backing the mobile swarm storage systems in Germany, too. V2G charging is set to become a viable opportunity with all VW electric models by the end of 2022 – and not just for the parent company's cars, but also for its brands Audi, Škoda and SEAT.

What advantages does Vehicle to Grid offer, and who can benefit from them?

1. Maximum storage capacity at minimum cost

V2G has the potential to harness immense power reserves from millions of electric cars in a matter of seconds.

This is illustrated by a simplified sample calculation: If all of the approximately 1 million electric cars registered in Germany were simultaneously connected to a wallbox with 11 kW of charging power each, their batteries could supply or absorb up to 11 GW of power. This is equivalent to the short-term flexibility of a good 2,500 modern wind turbines or 30 gas-fired power plants.

V2G technology is affordable and conserves resources to boot. Instead of producing additional storage implemented with high costs and resource requirements, it uses the batteries that are already available for mobility purposes. Storage couldn't get more economical or environmentally friendly.

2. Supporting the energy transition and using it as an opportunity to generate revenues  

V2G charging can also help to make electric cars more financially beneficial compared to cars with internal combustion engines. This is because their storage capacity can not only save money; it can earn it, too, due to the services provided in the energy system.

Owners of electric cars can join what are known as "aggregator pools", like those The Mobility House is currently technologically implementing in Germany. Pools like these bring together many electric cars that would be too small on their own to get directly involved in electricity trading. The aggregator buys low-cost, low-carbon electricity at a time when green power production is high and demand is low – on the likes of a stormy night or a sunny Sunday afternoon. It stores this electricity locally in the electric cars' batteries. When the wind drops or the sun sets, green power generation declines and fossil fuel-fired power plants have to be started up. This is the time to sell the stored electricity. It therefore replaces electricity generated from fossil fuels, at the same time as fetching a good price on the market.

The second service that battery swarms can provide for the energy transition is an "operating reserve", which acts as a cushion to compensate for fluctuations in the power grid. This allows grid companies to use electric car batteries to fine-tune supply and demand. An initial real project was implemented in 2018 by The Mobility House, Nissan, the energy company ENERVIE and the grid operator Amprion. It illustrated that a Nissan Leaf can "earn" a good €20 per week using this method. There is no need to fear that their battery will end up unexpectedly empty – a mere 10 to 20% of the storage capacity as a margin is sufficient for V2G charging. And since a car is stationary for an average of 23 hours a day, there is plenty of time. That way, electric cars can support the energy transition, bump up household budgets and still be fully charged at the desired time. There's no need to worry about the battery aging faster either, since both the car manufacturer and aggregator take this into account.

However, bidirectional charging isn't just interesting for private individuals; it's appealing to companies that run their own vehicle fleets (e.g. logistics fleets) too. This is especially true if the company vehicles are stationary at fixed times overnight, on weekends or during vacation periods. This means that energy companies with centralized battery plants aren't the only ones set to benefit from the energy transition; the winners will also include many people and companies that join forces to form a decentralized storage network. The Mobility House and several other innovative companies on the international scene have already demonstrated that Vehicle to Grid charging works in practice, cutting the costs of implementing a renewable energy system.