What is Bidirectional Charging?

Bidirectional Charging (also known as two-way charging) is an exciting EV technology that transforms your electric car into a power source. This allows electric vehicles not just to take in electricity for charging, but also to feed it back out for other uses.

This article explores the concept of bidirectional charging, its benefits, how it works, and its potential impact on the future of UK energy usage.

Ford mustang EV charging on a brick driveway

How does bidirectional charging work?

Bidirectional charging is a technology found in EVs that enables the flow of electrical energy to go two ways between an electric vehicle and out to other sources.

Here’s how it works:

  1. Charge the EV as normal
    This process is similar to regular charging, where energy from the power grid is used to charge the vehicle’s battery via a home EV charger or via a 3-pin EV granny charger. The car is plugged into a bidirectional charging station, and electricity flows from the grid to the vehicle.

  2. Reusing the EVs energy
    The flow of electricity is reversed. The charged battery in the electric vehicle can send power back out to either the grid (V2G), a home (V2H) or another specific purpose or ‘load’ (V2L).

This is possible when the vehicle is connected to a bidirectional charger, and the vehicle’s electronic system allows for energy to be returned and reused.

This unique feature of bidirectional charging opens up opportunities for EVs to serve as mobile energy storage systems, providing energy back to the grid during peak demand or emergencies. It can also enable homes to use their EVs as a power source during power outages or to reduce electricity costs by using stored energy during high tariff periods.

Not all electric vehicles or charging stations support bidirectional charging. The vehicle must be designed to allow the flow of electricity both ways without causing harm to its battery or electrical systems.

The charging station must also be specifically designed to handle two-way power flow.

What types of bidirectional charging are there?

There are three main types of bidirectional charging:

  • Vehicle-to-Grid (V2G)
    Vehicle-to-Grid (V2G) is the process where an electric vehicle returns energy to the power grid. This becomes especially useful during peak demand times or in cases of grid instability. Essentially, the vehicle serves as a portable energy storage system that can support the grid when required.

  • Vehicle-to-Load (V2L)
    Vehicle-to-Load (V2L) is when an EV’s stored energy can be used to power other electrical devices or loads. This can range from small appliances like a laptop or mobile phone to larger equipment like a portable fridge or other equipment.

    V2L functionality can be extremely beneficial for outdoor activities like camping.

  • Vehicle-to-Home (V2H)
    Similar to V2G, Vehicle-to-Home (V2H) involves using the EV’s battery to supply power, but in this case, the power is used directly by the home, rather than being returned to the grid. 

    In a V2H setup, an EV can act as a backup power source for a house during a power outage or it can supply power during periods of high electricity tariffs to save on energy costs.

All three of these need bidirectional charging to work, where the flow of electricity is not just from the grid to the vehicle (as in traditional charging), but can also be from the vehicle to the grid, load, or home.

What are the benefits of bidirectional charging?

Bidirectional charging has a number of benefits for both EV owners, the grid & the environment:

  • Grid stability and reliability
    With bidirectional charging, EVs can feed electricity back into the grid during periods of high demand, helping to stabilise the grid and prevent blackouts.

    They can also help balance the grid by consuming excess power during off-peak times and returning it during peak times.

  • Cost savings
    EV owners can save on their electricity bills by charging their cars during off-peak hours when electricity prices are lower and then using the stored energy in their EVs to power their homes during peak hours when electricity prices are higher.

  • Emergency power supply
    In case of a power outage, a bidirectionally-charged EV can act as an emergency power supply for a home or a business, providing electricity for essential appliances and devices.

  • Renewable energy
    Bidirectional charging can help integrate more renewable energy sources into the grid. When there’s excess production from sources like wind or solar, the electricity can be stored in EVs. This stored power can then be fed back into the grid when renewable energy production is low.

  • Financial incentives
    Eventually, we could see UK utility companies offer financial incentives to EV owners who use vehicle-to-grid charging, providing an additional source of income or credit towards their electricity bills.

  • Sustainable energy consumption
    Bidirectional charging contributes to more sustainable energy consumption patterns, which is crucial for environmental sustainability.

Are there any negatives to bidirectional charging?

While bidirectional charging presents plenty of benefits, there are also some drawbacks to consider:

  • Battery wear
    If you are constantly charging and discharging your EV, the battery will wear out quicker.

  • Infrastructure costs
    The initial setup for bidirectional charging, including a compatible car and a bidirectional charger, can be costly. Infrastructure for wide-scale V2G deployment also requires substantial investment.

  • Limited compatibility
    Not all electric vehicles and charging stations support bidirectional charging. Manufacturers and charging equipment makers need to work together to create compatible standards for the tech.
standard unidirectional EV charger mounted on a wall
Standard EV chargers in the UK are not bidirectional

Can any electric vehicle use bidirectional charging?

Not all electric cars are capable of bidirectional charging. The EV must be specifically designed to manage the two-way flow of electricity safely.

One of the early adopters of this technology was Nissan with its LEAF model, which can use a technology called CHAdeMO for both charging the car and allowing it to give energy back to the grid or home. 

Mitsubishi’s Outlander PHEV also supports bidirectional charging.

Which cars have bidirectional charging?

The list below is the current EVs on the market with bidirectional charging capabilities, they are all able to feed power back into the grid, your home, or other electrical loads:

  • BYD Atto 3
  • Fisker Ocean
  • Ford F-150 Lightning
  • Genesis G80
  • Genesis GV60
  • Genesis GV70
  • Hyundai Ioniq 5
  • Hyundai Ioniq 6
  • Kia EV6
  • Kia Niro EV 2023
  • MG MG4
  • MG ZS EV
  • Mitsubishi Outlander PHEV
  • Nissan Leaf (from 2013)
  • Polestar 3 (from 2024(
  • Volkswagen ID Buzz

What infrastructure is needed for bidirectional charging?

The widespread adoption of bidirectional charging in the UK will need five key pieces of infrastructure:

  1. Bidirectional charging stations
    These are specialised charging stations equipped to handle the two-way flow of electricity. 

  2. Compatible electric vehicles
    The electric car must have the necessary hardware and software that allow for the safe flow of electricity in both directions. This includes specialised inverters and onboard chargers capable of managing power flow to and from the battery.

  3. Grid connectivity
    The grid itself needs to be capable of receiving power back from EVs. This can require infrastructure, system improvements and household electricity upgrades, particularly in areas with older electricity networks.

    UK trials have recently taken place but we still don’t know the results on how the grid has performed.

  4. Energy management systems
    These are necessary to optimize the charging and discharging process based on various factors, such as electricity tariffs, UK national grid demand, and the user’s driving needs. An energy management system can decide when it’s most economical to charge or discharge the vehicle.

  5. Regulatory framework
    UK policymakers need to create regulatory frameworks that support the use of EVs for grid services. This can include measures to ensure safety, reliability, and fair pricing, as well as government incentives to encourage the use of bidirectional charging.

Bidirectional EV chargers in the UK

INDRA, based in the UK, are one of the world leaders in EV bidirectional charging. They have made significant strides in advancing bidirectional charging technology.

INDRA were the first to demonstrate the practical application of large-scale domestic vehicle-to-grid (V2G) technology through the Project Sciurus V2G trial. Currently, they are expanding their focus to include V2H technology, conducting extensive trials to maximize its potential benefits.

INDRA’s V2H system is its economic benefit to consumers. It offers significant savings on energy bills, with the potential to save up to £200 a month. It also contributes to environmental sustainability by reducing carbon emissions and promoting more efficient energy use. The system allows for the storage of solar energy in the EV battery, which can be used later, thereby reducing dependence on the grid.

What is unidirectional charging?

Unidirectional charging is when the power flows in one direction only — from the electric grid to the electric vehicle. It’s the common method of charging EVs.

When an EV is connected to a charging station, electricity is drawn from the grid and used to charge the vehicle’s battery. The charging station regulates the power flow, ensuring the battery is charged efficiently and the EV is charged safely.

This process is unidirectional because the power only moves in one direction: from the grid to the vehicle. The vehicle cannot send power back to the grid or to another device or system.

What is Two-Way charging?

Two-way or 2 way charging is another name for bidirectional charging. So Two-way is a method of charging electric vehicles that allows for the transfer of electricity in both directions.

Not only can the EV take power from the grid or a charging station to charge its battery (as in traditional, or unidirectional, charging), but it can also send power back to the grid or another system or device.

When will all EVs have bidirectional charging?

Several leading EV makers are actively integrating bidirectional charging into their lineups. However, there’s no specific timeline for when all EVs will have this feature, as adoption rates vary across manufacturers.

  1. Progress Among Manufacturers: BMW, Volvo, and Porsche are testing bidirectional functionality. Tesla plans to support bidirectionality in all its models by 2025.

  2. General Motors’ (GM) Rollout: GM is incorporating Vehicle-to-Home (V2H) charging as a standard feature starting with the 2024 Chevrolet Silverado EV RST. This rollout will continue with several other models, including the 2024 GMC Sierra EV Denali Edition 1, 2024 Chevrolet Blazer EV, 2024 Chevrolet Equinox EV, 2024 Cadillac Lyriq, and the 2025 Escalade IQ.

Given these developments, while we can see a clear trend towards the adoption of bidirectional charging in new EV models, but an accurate timeline for when all EVs will have this feature is not easy to work out yet. It will likely depend on a combination of technological advancements, regulatory changes, and the strategies of individual carmakers.

The final word on EV bidirectional charging

Bidirectional charging is a revolutionary technology that extends EV use far beyond just driving to the shops!  Unlike traditional charging, bidirectional charging enables power to flow in both directions, not only from the grid to the vehicle but also from the vehicle back to the grid, home, or other electrical loads.

This two-way power flow provides myriad potential benefits, including grid stabilisation, better integration of renewable energy, cost savings for EV owners, emergency power supply, and more sustainable energy consumption patterns.

Bidirectional charging works through advanced power electronics within the EV and the charging station. It requires specialised infrastructure including bidirectional charging stations, compatible electric vehicles, advanced energy management systems, robust communication systems, and supportive regulatory frameworks.
 
Despite some drawbacks such as potential battery wear, initial setup costs, and limited compatibility, the potential benefits of bidirectional charging have led to increased interest and development in this area.

Looking ahead, as more electric vehicles with bidirectional charging capabilities enter the market and as the necessary infrastructure continues to evolve, bidirectional charging is set to play a significant role in the broader transition to a more resilient, efficient, and sustainable UK energy system.


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