What is vehicle-to-grid or V2G?

And what if electric cars could be used to store electricity, as well as carrying us around? This is the idea of 'vehicle-to-grid' or V2G.

This technical concept is based on the idea of using the batteries in parked electric cars in both directions and with flexibility to:

1. take in and store electricity that is produced in excess on the network;
2. constitute an electricity reserve to power the grid or a home network when needed.

What is the point of vehicle-to-grid?

V2G can help you to reduce your energy bills and CO2 emissions. It offers benefits for both electric vehicle owners and for the electricity grid as a whole.

• Lower electricity costs: the option to use the vehicle's battery as energy storage for the home (vehicle-to-home or V2H).
• Additional income: payment for making the battery available to the grid and the option of selling stored electricity to the grid (flexibility).
• Reducing your carbon footprint: contributing to the integration of renewable energies and actively participating in the energy transition.
• Stabilising the electricity grid: helping to balance electricity supply and demand and smooth out consumption peaks.
• Return on investment: use of the battery for more than just mobility and faster recovery of vehicle purchase costs.

What is the potential in Belgium?

In 2040 there will be between 900,000 and 2.5 million electric vehicles in Belgium alone. This is what a study by Elia, the Belgian transmission system operator, reveals. 

However, we know that cars, whether electric or not, spend much more time parked than driving around. We would end up with hundreds of thousands of electric cars parked for one hour or a whole night.

Connected to their terminal and with a full battery, these cars would therefore make up a huge reserve of electricity. The potential of "wheeled storage" is therefore very real.

Not without smart technologies

To work properly, vehicle-to-grid must consider:

• the needs of the car drivers: in the morning, they must be able to rely on enough battery autonomy, for example to get to work
• moments when renewable electricity is produced in excess: mid-day in summer for solar panels. When winds are strong, especially in winter and at night, for wind turbines
• peaks in electricity demand: in Belgium, in the morning around 8:30am and in the evening from around 6:00pm to 7:00pm
• electricity prices: car batteries could also provide houses with cheap electricity instead of allowing households to consume electricity at peak times in the morning or evening.

Technology in the making

In Belgium, 3 manufacturers already offer V2G DC charging stations. You can view the list of approved systems on the Synergrid website.

The new Renault 5 E-Tech electric, due to go on sale in 2024, will be equipped with a bidirectional on-board charger for injecting alternating current (AC) electricity. This technology should reduce the price of bidirectional charging stations and help make V2G more accessible.

Vehicle-to-home or home battery?

On average, a four-person household consumes around 10 kWh of electricity per day.

Home batteries generally have a capacity ranging from 5 to 10 kWh. In comparison, electric car batteries are much more powerful, with capacities ranging from 65 to 100 kWh.

This capacity is enough to supply a house for more than a week. The use of a small part of this capacity for domestic supply therefore has no significant impact on the vehicle's range.

However, the home battery is a fixed installation which is permanently available. On the other hand, the mobile nature of an electric vehicle means that it can only contribute to the domestic power supply when it is on site.

A second life for electric vehicle batteries

Batteries from electric vehicles will be added to the home battery bank which develops in parallel.

Car batteries do, in fact, gradually lose their capacity. After a few years, this capacity is no longer sufficient to provide enough autonomy for a car, but the battery’s performance is still sufficient to power a building’s electrical system.

It is therefore expected that a secondary market will develop for 'retired' car batteries as home batteries.