V2G Explained - Benefits of Vehicle-to-grid Technology
What is Vehicle-to-grid?
Vehicle-to-grid (V2G) technology allows an electric vehicle (EV) to send power into the electricity grid using a bidirectional (two-way) charger controlled via a remote management system. Some vehicles with V2G can also be used to supply backup power. However, V2G should not be confused with Vehicle-to-home (V2H) or Vehicle-to-load (V2L), where the vehicle is used to power a home or loads rather than send power to the grid. Learn more about the difference between V2G, V2H and V2L here.
How does V2G work?
V2G technology allows an electric vehicle to synchronise with the electricity grid and inject power back into the grid using a specialised bidirectional charger. These advanced devices contain sophisticated power converters that can either charge the EV battery or send power back to the grid when instructed, such as in times of high power demand to help stabilise the grid. However, for it to function, the following three prerequisites are required:
An electric vehicle with V2G capability.
A compatible bidirectional charger.
The owner must participate in a V2G program such as a VPP.
V2G technology can help stabilise the electricity grid by paying individuals to allow the local grid operator to use some of their EV battery capacity for grid support services. However, you cannot simply connect a bidirectional charger to an EV and start feeding power into the grid without having approval from the grid operator. For it to work, the grid operator must be able to manage the bidirectional charger remotely and control the amount of energy injected into the grid. This remote management is typically done via a Virtual Power Plant program (VPP), which we explain later.
“an average EV has a battery capacity of 60kWh, which is six times larger than a typical 10kWh home solar battery and around three times more energy than an average household uses per day”
Basic diagram of a vehicle-to-grid system with an optional solar system connected.
V2G compatible EVs
The Nissan Leaf is one of few V2G capable EVs
Only a few EVs currently have V2G bidirectional capability; these include the later model Nissan Leaf (ZE1), Nissan e-NV200, Mitsubishi Outlander and Mitsubishi Eclipse plug-in hybrids. While these vehicles have been available for several years, the technology is still in the trial phase in most countries.
As we transition towards a more decentralised renewables-based energy system, automotive vehicle manufacturers are starting to recognise the many benefits of V2G and implementing bidirectional charging technology into future EV platforms. Several well-known manufacturers, including VW and Volvo, are known to be developing EVs with V2G capability. More recently, Hyundai deployed 25 modified IONIQ 5 vehicles for a Vehicle-to-Grid trial in the Dutch city of Utrecht. The city, along with mobility provider We Drive Solar, is striving to deploy V2G technology on a large scale in an attempt to become the world’s first bi-directional powered region. In early 2023, Tesla’s senior vice president mentioned the company would be integrating bidirectional charging capability in their next-generation vehicles, indicating it may be available by 2025. However, there is still no official confirmation that Tesla will include V2G, V2H or V2L technology, despite the surge in interest and the vital role these technologies will undoubtedly play.
List of EVs with V2G bidirectional DC charging
| Vehicle | Connector Type | V2G | V2H | V2L | Available |
|---|---|---|---|---|---|
| Nissan Leaf ZE1 | Chademo | YES | YES | No | Now |
| Outlander PHEV | Chademo | YES | YES | No | Now |
| Hyundai Ioniq 5 | CCS | No | No | YES | Now |
| KIA EV9 | CCS | YES* | YES* | YES | 2024 |
| KIA EV6 | CCS | (TBC) | (TBC) | YES | Now |
| Ford F-150 Lightning | CCS | (TBC) | YES* | YES | Now |
| VW ID Models | CCS | (TBC) | (TBC) | (TBC) | 2024 |
* V2G functionality included but yet to be enabled by the manufacturer (software update required)
What is a bidirectional charger?
Wallbox Quasar bidirectional charger
A bidirectional charger is an advanced two-way charger that can charge and discharge an EV battery. Compared to regular EV chargers that charge using AC (alternating current), bidirectional chargers can convert AC to DC (direct current) when charging and convert DC battery power back to AC which is sent back into the grid. However, this advanced power conversion comes at a price, and bidirectional chargers are still expensive due to the sophisticated power electronics needed.
Only a few bidirectional V2G chargers are available for purchase, the most well-known being the Wallbox Quasar. However, several companies have announced V2G chargers with advanced features, such as backup power, enabling vehicle-to-home V2H capability. V2H can power a home and allows an EV to store excess solar energy like a home battery system. These multipurpose chargers are often called V2X chargers. Learn more about the various V2G chargers in our detailed bidirectional chargers explained article.
EV Battery capacity (kWh)
Before we explain the benefits of using V2G, it helps to understand the massive energy potential of EVs. Regular passenger vehicles spend most of their time parked at home or work. Unlike regular ICE (petrol/diesel) vehicles, electric cars have large, powerful battery systems that can be utilised when parked, thus providing an alternative use for these untapped energy sources. For instance, an average EV has a battery capacity of 60kWh, six times larger than a typical 10kWh home solar battery and around three times more energy than an average household uses per day, which is closer to 20kWh. So, just one EV could potentially power a home for several days in needed. This is particularly important to those vulnerable to natural disasters and associated power outages, which have become increasingly common over the last decade due to climate change.
Bidirectional charger standards
One reason Vehicle-to-grid has been very slow to roll out is that standards around V2G are difficult and complex. These standards involve regulating the power, safety, and electrical requirements when discharging energy into the grid. These standards are still under development and are similar to solar inverter standards and requirements. UL9741 is a new proposed safety standard for bidirectional EV charging system equipment. This standard is built around the UL1741 (safety standard) and the IEEE1547 standard for interconnecting distributed energy resources (DER) with electrical power systems.
The ISO standard 15118 specifies Vehicle-to-Grid Communication Interface between electric vehicles or plug-in hybrid electric vehicles and the Electric Vehicle Supply Equipment (EVSE) or EV charger. While V2G trials are taking place, industry and governments are working hard to develop and finalise standards to ensure that V2G technology can safely integrate with grid networks worldwide. In Australia, the current AS/NZS 4777.2 standard (Grid connection of energy systems via inverters) is under revision to include bidirectional inverters enabling V2G and V2H functionality. This is expected to be released in late 2024 or early 2025, enabling the sale and installation of bidirectional inverters across Australia and New Zealand.
Benefits of V2G
V2G technology can enable thousands of EVs to work in unison and act as a large distributed energy system, providing valuable services to the power grid. One way it can do this is by supplying energy during periods of peak demand, and charging up during periods of low demand, effectively balancing the grid. This orchestra of EVs or fixed battery systems is referred to as a Virtual power plant (VPP), explained below. For instance, when an EV is plugged in, excess energy can be sent back during a heat wave when the grid needs more capacity to meet the extra demand from air-conditioning. In contrast, EVs can also charge during times of excess supply, such as when the wind is blowing on a sunny day or when electricity costs are down due to low demand.
Virtual power plants - VPPs
V2G technology enables EV owners to earn money or credit by participating in Virtual Power Plants, also known as demand response programs. People participating in VPPs are paid for letting the grid operator or an energy retailer use some of the EVs or home battery to help meet grid demand. VPPs typically use cloud-based software to control thousands of battery systems to create a virtual large-scale generator or storage system. However, not all participants may be available or allow their vehicles to be used. The EV owner may set preferences for when they want their EV to charge or discharge. For instance, they may enable the vehicle to discharge during the peak evening hours when electricity rates are higher, thus earning revenue, and charge during the cheaper off-peak hours or when there is excess renewable generation. The participant or VPP program may also limit use to only emergency situations where the grid may suddenly experience a surge in demand or a sudden lack of supply.
The South Australian grid currently has the highest penetration of wind and solar in the world, and the local grid network operator (SAPN) is now the first in Australia to allow network connection of V2G bidirectional chargers. See the full SAPN V2G media release. Additionally, Australian energy retailer AGL recently concluded the first internationally recognised VPP trial in South Australia, using 1000 home battery systems to help balance grid demand.
Balancing the grid
One of the key benefits of V2G technology is that it can help reduce the need for expensive gas "peaker" power plants commonly used to supply excess power during times of high demand. In many countries with unregulated (market-based) power grids, such as Australia, gas-peaking plants generally set the wholesale electricity price. This has become problematic as gas prices skyrocketed in 2022 due to supply shortages, and in turn, electricity prices have also surged by a similar margin. In comparison, decentralised energy sources such as wind, solar and battery systems, including EVs, have very low fixed operating costs and thus can reduce the cost of electricity. However, due to the intermittent nature of wind and solar, firming or battery storage is sometimes required to buffer the variation in output. This is where V2G technology can assist, as it acts as a buffer to integrate more renewable energy sources, like wind and solar, into the grid.
Frequency regulation
Electricity grids use alternating current (AC) and operate at a frequency of either 50Hz or 60Hz. For electricity generators, including nuclear, gas, solar and wind, to work in unison, the grid frequency must be very stable, and this is where frequency regulation is essential.
V2G can also be used for frequency regulation, which helps stabilise the grid by quickly responding to sudden changes in supply or demand. For example, if a large GW (Gigawatt) scale thermal coal or nuclear generator suddenly trips due to a fault, the frequency can rapidly fall to the lower operational limit; this can have serious flow-on effects and even cause other generators to trip off. Currently, gas-peaking plants and large-scale grid batteries combined with grid-forming inverters are being used in many countries to help maintain grid frequency. EVs participating in VPPs programs can work in much the same way. The combined energy of thousands of EVs can easily reach a gigawatt scale and be deployed rapidly when vehicles are parked in homes and garages during the evening peak electricity demand period. However, one of the biggest challenges of using V2G for frequency regulation is synchronising all the V2G-enabled vehicles with precision timing using a reliable cloud-based control system.
Backup power
Bidirectional inverters used to enable V2G are not only used to provide grid support. These powerful devices contain power inverters, and most new bidirectional chargers can also enable backup power in the event of a blackout or emergency. However, for a bidirectional inverter to power a house independently of the grid, it must first isolate from the grid network, known as islanding. This capability is the same as vehicle-to-home (V2H) but should not be confused with vehicle-to-load (V2L), where the inverter is inside the vehicle. Learn more about backup power using bidirectional chargers here.
Issues and Challenges Implementing V2G
While V2G technology has the potential to revolutionise the way we generate and use energy, many technical challenges still need to be overcome. Currently, several trials are being conducted worldwide to help understand how V2G technology can be used and regulated. At this stage, the primary issues preventing the widespread adoption of Vehicle-to-Grid technology include the following:
Lack of standardisation: There is currently no standard protocol for V2G communication and grid interaction, making it difficult for different V2G systems to interoperate. However, these are currently under development.
High costs: The cost of bidirectional chargers is currently high, which makes it difficult for individuals to justify the investment.
Regulation: The regulatory environment surrounding V2G technology is still uncertain, and different countries, regions and grid operators have different regulations and incentives.
Safety: There are concerns about the safety of V2G systems, particularly in the event of power grid failure where the bidirectional inverter must disconnect from the grid while it is being repaired.
Limited EV options: Very few EVs that are compatible with bidirectional charging are available.
Despite these challenges, V2G technology has enormous potential in an increasingly decentralised energy system and may even hold the key to creating 100% renewable power grids.
Will V2G reduce EV Battery Life?
There are concerns that employing an electric vehicle for Vehicle-to-Grid services may diminish the battery's lifespan as a result of more frequent discharging. While this concern is valid, it's important to note that the discharge rate and energy consumption during V2G services are very low compared to the demands placed on the battery during typical EV driving scenarios.
For example, most V2G chargers are rated at 8 to 10kW; in comparison, when driving an EV, the power consumption will generally be closer to 20kW while cruising and often well over 100kW when accelerating. Thus, when an EV is used for V2G, the battery will be under very little stress and will not heat up or drain quickly. Additionally, the limited data available shows that V2G services generally only last for 1 or 2 hours, so the amount of energy discharged on a daily basis will be relatively low. For instance, an average EV battery is 60kWh, so at full power, only 10kWh or 16% of the battery capacity will be used if the V2G service lasts 1 hour. Unless the vehicle is used for V2G services every day for a prolonged time, which is presently not the case, there will be minimal effect on the battery life. Additionally, as the percentage of electric vehicles increases and thousands more EVs can participate in grid (V2G) services, the demand per EV will reduce.
The research paper “Impact of V2G service provision on battery life” in the Journal of Energy Storage also supports the assertion that V2G will not substantially impact battery life if the discharge rate is maintained at a low level.
The latest generation EV batteries are engineered to have a 300,000 to 500,000km lifespan, so rough calculations suggest regular V2G use may reduce the lifespan by 50,000km, or approximately 10 to 12%. However, the real-world use of V2G services will evolve as the grid becomes more decentralised and increasingly renewable-powered. That being said, EV battery technology is also continuously improving. Next-generation solid-state batteries are expected to have a one million-mile lifespan, so the detrimental effects of regular V2G use will likely be reduced further.
