Using Your Electric Car as a Home Battery

Energy costs make up a significant share of every household's expenses. Solar panels and home batteries are examples of measures you can take to reduce these costs, but they obviously require a substantial investment. Did you know you can use your electric car's battery as your home's battery? Below, our blogger Alain Dierckx explains how.

From your electric car's battery to your home

As the owner of a suitably equipped electric car, you can use the energy from the car's battery for household use. This can reduce your energy bills, since it lets you, for example, use your car as a home battery when electricity prices are high.

What are the benefits?

Using your car's battery as a home battery offers certain advantages:

• You save the cost of a home battery;
• An electric car battery produces more energy than an average home battery because it has more power (more kWh);
• Feeding the energy produced by your car's battery back into the grid can earn you financial compensation from the distribution network operator;
• Electricity produced by your solar panels and stored in your car's battery can be used by your household when electricity prices are high;
• Even without solar panels, discharging the energy stored in your car's battery can be worthwhile, provided the charging took place at a time when energy was cheaper.

What's the return? It's hard to calculate the exact return on using your car's battery, since electricity prices fluctuate daily and depend on the contract signed with your energy supplier. If your vehicle is often at home, it's certainly an interesting solution.

Finally, feeding the car battery's energy into the general electricity grid also has a benefit. Indeed, it ensures grid stability and helps absorb peaks and troughs in production.

What are the drawbacks?

• You need a suitably equipped electric vehicle. To be able to use an electric vehicle's battery energy for your household, the vehicle must be fitted with the right technology. This comes at an extra cost that can reach several thousand euros depending on the make and model;
• You need a suitable charging station. To discharge your car battery's energy and send it back to the grid or to your home, you need a bidirectional charging station. It must always be certified, and there is a reporting obligation to the distribution network operator Fluvius. Today, unfortunately, there are very few bidirectional charging stations on the market;
• You may need to modify your connection installation. To perform bidirectional charging, it may be necessary to modify your home's electrical system;
• Wear on the car battery. Opinions are currently divided on this point. With more intensive use of the car battery, some say it wears out faster, while others see it as an advantage, since it helps keep the battery in better condition. Further research is underway on this topic.

What does a bidirectional charging station cost?

Expect a total cost (charging station + installation) of 5,000 to 10,000 euros. Today, the authorities grant a tax incentive for the purchase of certain types of charging stations. You'll find an overview of these measures on this website.

What are the concrete possibilities?

Different terms and abbreviations are used to describe the features of these special types of electric vehicles and charging stations.

V2X (vehicle to everything) is the general term describing vehicles connected to their environment. Depending on where the energy goes, three categories are distinguished:

V2G (vehicle to grid)

Cars fitted with this technology can only supply their energy to the general electricity grid. This can be done by installing a charging station or via a smartphone app.

For V2G, a bidirectional charger is always required. Check beforehand with the network operator to find out whether V2G is possible where you live.

V2H (vehicle to home)

With this option, you connect your car's battery to your home's electrical network. This can be done by installing a charging station or via a smartphone app. You also need a bidirectional charger for V2H.

V2L (vehicle to load)

Via an adapter or a socket, suitably equipped electric vehicles can power specific devices, for example an electric bike, an electric stove, another electric car, etc.

No bidirectional charger is needed for this. V2L-compatible vehicles have an internal DC-to-AC converter and a socket for connecting devices directly.

Which makes and models can charge bidirectionally?

Today, not all electric cars have the technology mentioned above. In fact, the range is still very limited so far, but it is gradually expanding.

Can an old battery be used as a home battery?

Old electric car batteries can be reused as home batteries. Although they can no longer be used in vehicles due to their reduced capacity, they often still have enough storage capacity for applications such as home batteries.

This solution is sometimes cheaper than buying a new home battery. However, the conversion requires technical expertise, since batteries aren't always designed to be easily dismantled or modified. Get informed and seek help from a professional.

Can my home battery also charge my car's battery?

Yes, but under certain conditions:

• The home battery and the electric car must be compatible in terms of power and charging protocol;
• You generally need a charging station or wall box connected to your home battery. This charging station must be compatible with your car and forms the connection between your home battery and your car;
• The capacity of your home battery also plays an important role. Car batteries generally have a larger capacity than home batteries, so your home battery can only charge a small part of the car.

It's best to contact the manufacturer of your home battery and your charging station to check the options.