Bidirectional EV Chargers - What They Are and Do You Need One

One of the biggest developments in EV chargers in recent years has been bidirectional charging, often called vehicle-to-grid or vehicle-to-home charging.

But what exactly is a bidirectional EV charger, what do they do, and should you buy one?

You’ll learn all this and more in our complete blog post below.

Let’s get right into it:

What is Bidirectional Charging, and How Does it Work?

As the name might suggest, bidirectional charging is an EV charger that allows electricity to flow in both ways.

This is different to a unidirectional charger (that you’ll likely use on your electricity vehicle) where electricity flows from the electrical grid to your vehicle. 

Instead, bidirectional EV chargers allow electricity to follow from the electrical grid to the vehicle and from the vehicle to the electrical grid.

Here’s how it works:

When using a unidirectional charger, the AC current from the grid gets converted to a DC current that your car can use to charge itself.

This conversion is typically handled by the car's own converter, but it’s common to have a converter found directly in the charger.

The conversion is usually a one-way process, but bidirectional chargers allow the DC to be converted back to AC.

What is Bidirectional Charging Used For?

Bidirectional chargers can convert AC to DC and back again. 

But what exactly is the point?

Well, there are four main use cases where bidirectional chargers could change the game for EV car owners.

Vehicle to Grid (V2G)

Vehicle-to-grid charging is when a bidirectional charger converts the DC electricity back to AC and sends it back to the electrical grid.

On the surface, it may seem like a pointless exercise (after all, what’s the use of charging your car up only to remove the electricity shortly after?) but take a closer look, and you’ll see the benefits can be huge.

So let’s say you’ve charged your car in the evening as energy prices are lower outside of peak times.

You then commute to work in the morning and park up.

With a bidirectional charger, you can leave your car plugged into the grid during the day (assuming you’ve got access to a charger at work) and give the electricity back during peak hours when you aren’t using your car.

Not only could this help out your local power grid by turning your car into a mobile power bank, but you could also sell the electricity back during peak hours when energy prices are higher for a profit.

While we’re likely years away from seeing the right infrastructure in place to support this, the potential behind bidirectional chargers is huge.

Vehicle to Home (V2H)

Using the same principles as V2G charging, vehicle-to-home charging means using a bidirectional EV charger to convert the DC electricity from your battery to AC for your home. 

As a practical example, let’s say you get home from work on a Friday evening and charge up your car.

But come Saturday and Sunday, you don’t do much travelling and instead stay at home all day.

Here, with the help of a bidirectional charger, you can use the cheaper electricity you bought in the evening for your car and send it back to your home during peak hours without paying for the peak electricity prices.

A fully charged EV battery can usually hold around 60kWh of electricity, which is enough to power a home for two days. 

While you’ll be helping alleviate the stress on the electricity grid during peak hours, you’ll also be saving money by reusing your car’s electricity.

In emergency situations or power outages, a bidirectional EV charger can also become a reliable backup power source to keep the lights on and appliances running.

Vehicle to Load (V2L)

Vehicle-to-load is the most basic form of bidirectional charging.

Here, you can use your electric vehicle to charge smaller equipment and appliances, such as during a camping trip.

Vehicle to Vehicle (V2V)

The final use case for bidirectional charging is another form of V2L charging.

Here, you can use your EV to power another person's EV that has run out of charge.

In many ways, it’s similar to giving another car a “jump”, like we see in petrol and diesel-powered vehicles.

Summary

So the main uses for a bidirectional charger are:

• Energy bill reduction: You can strategically charge your EV when rates are low and use the stored energy when costs are high.
• Integration with renewable sources: If you're using solar panels, you can store surplus energy in your EV, ensuring you make the most of the sun’s power.
• Participation in grid services: Some programmes in the UK pay you for contributing energy back to the grid during peak demand. This not only helps balance the grid but also turns your EV into a source of passive income.
• Smart home support: With the right technology, your EV can automatically decide when to store energy, when to use it for your home, and even when to send it back to the grid.

Pros and Cons of Bidirectional Charging

So, bidirectional chargers are the future, and you should buy one right now, right?

Not quite. While bidirectional chargers have a lot of promise, there are some cons to be aware of.

Fundamentally, the main pros of a bidirectional charger are:

• Lower energy costs by charging during off-peak hours and selling excess power back to the grid.
• Increased energy security for your home through vehicle-to-home energy supply.
• Improved grid stability by providing energy during peak demand.

However, the main cons to consider are:

• Compatibility: Not all EVs support bidirectional charging, which may limit your options if you're in the market for a new car.
• Installation costs: Setting up a bidirectional EV charger can be more expensive due to the advanced technology involved.
• Warranty concerns: Some manufacturers may not cover the use of your EV's battery for home energy purposes, which could impact your vehicle's warranty.
• Infrastructure: The UK is potentially years away from making bidirectional chargers a viable option.

Bidirectional EV Chargers vs Traditional EV Chargers

Which Electric Vehicles Have Bidirectional Charging?

The main issue with bidirectional charging is the amount of cars that support it.

As of September 2023, there were 9 cars sold that support any form of bidirectional charging, including:

• Ford F-150 Lightning (V2G)
• Genesis GV60 (V2L)
• Hyundai Ioniq 5 (V2L) 
• Hyundai Ioniq 6 (V2L) 
• Kia EV6 (V2L) 
• Kia Niro (V2L) 
• Mitsubishi Outlander PHEV (V2L) 
• Nissan Leaf (V2H, V2G)
• VW ID.4 (V2H)

Frequently Asked Questions

What are bidirectional electric vehicle chargers?

Bidirectional electric vehicle chargers allow electricity to flow in two directions: they can both charge an EV and send stored energy back to the power grid or to a home.

How can bidirectional chargers save on energy bills?

By allowing EV owners to sell excess energy back to the grid during peak demand times, bidirectional chargers can save on energy bills through reduced electricity costs or incentives from energy suppliers.

Can bidirectional chargers integrate with renewable energy?

Yes, bidirectional chargers can be integrated with renewable energy sources like solar or wind, storing excess renewable energy and supplying it back when needed, enhancing energy self-sufficiency and sustainability.

Are all EVs compatible with bidirectional charging?

Not all EVs are compatible with bidirectional charging as of now. Compatibility depends on the vehicle's charging technology and manufacturer specifications.