Vehicle-to-Grid or a Home Battery?

Vehicle-to-grid (V2G) and a home battery both store electricity and both can move it back out again, but they are not the same purchase. A home battery is a fixed asset in the house that is always available. A V2G system is a bidirectional charger plus the car parked on the drive, and it only works when the car is there and plugged in.

The cost gap is the reason the comparison matters. A 7kW home EV charger costs around £900 to buy and install¹. A V2G charger has historically carried a large premium over that: around £4,000 in 2021², falling to around £3,700 above a smart chargepoint by the end of the Sciurus trial³, with the V2G Britain report projecting a premium of between £656 and £1,164 by 2030⁴.

The earnings gap runs the other way. Ofgem's case study of the Sciurus trial reports customers earning as much as £725 a year without doing anything except keeping their car plugged in⁵. A home battery earns nothing directly; it saves money by shifting cheap off-peak electricity to expensive hours⁶.

Vehicle-to-grid and a home battery: what each one actually is

V2G is a technology that allows electric vehicles to draw power from the grid to charge their batteries and also to send electricity back to the grid when needed, generating cash for the EV owner⁸. The Welsh Government's national standards for EV infrastructure describe it more broadly as the use of vehicle batteries as storage to help balance supply and demand on the electricity network, applying at scales from individual batteries up to aggregation of multiple batteries across one or multiple carparks⁹.

The narrower term is vehicle-to-home, or V2H. Electricity Networks describe V2H as utilising the energy to power a home rather than delivering it back to the grid⁸. Uswitch's glossary frames the same capability as releasing power back through the charger either for use in the building it is connected to or back into the grid in general¹⁰. The Climate Change Committee uses V2X as the umbrella term: it allows electric vehicles to operate bidirectionally, charging from the grid but also discharging to the grid, building or home as needed¹¹.

A home battery is a different proposition. It sits in the house, wired to the consumer unit, and stores electricity for later use. The IAAS guide notes the technology splits between lithium-ion and lead-acid batteries¹². The National Energy Action best practice guide describes the non-solar use case plainly: electricity is used to charge the battery during cheap-rate periods and used later when electricity is more expensive, for example using Economy 7, Economy 10, or more innovative time-of-use arrangements⁶.

The core difference: a battery is always there, a car comes and goes

The decisive difference is availability. A home battery is on site every hour of the year. A V2G system depends on the car being parked and plugged in, which is why plug-in behaviour drives the modelled returns so heavily.

The V2G Britain report models a 7kW V2G charger achieving annual revenues of around £436 above smart charging for a high plug-in rate archetype, where the car is connected 75% of the time⁴. That archetype is the point: the revenue depends on the car being at home and connected, not on the hardware alone.

Home battery economics rest on the same principle but with a fixed asset. The Energy Systems Catapult's Living Lab data shows homes with batteries consistently have lower total daily grid consumption across three seasons, with strong overnight charging peaks across autumn, winter and spring consistent with energy arbitrage on time-of-use tariffs¹³. Winter consumption in those homes rose, which the Catapult attributes to a suspected arbitrage pattern¹³.

There is a second difference in what the asset is for. A car has to be ready to drive. A home battery has no other job. That matters for how much of the stored energy a household is willing to commit, and it matters for warranty terms, which for vehicles are set by the manufacturer rather than the charger maker.

What V2G can earn, and what a home battery can earn

V2G earnings figures in the public record span a wide range, and the spread comes from assumptions rather than from hardware. Ofgem's case study reports customers in the Sciurus trial earning as much as £725 a year without needing to do anything except keep their car plugged in⁵. Cenex modelling of Sciurus trial data put V2G at around £410 per year compared with unmanaged charging². The V2G Britain report models around £436 a year above smart charging for a 7kW charger at high plug-in rates⁴, and a net annual revenue of £278 per battery electric vehicle in its stacked case for customers with solar and high plug-in rates in a constrained area⁴.

The comparison against smart charging turns on whether grid services are accessible. The V2G Britain report states that, including grid services, smart charging captures 40% of the total value of V2G for low plug-in scenarios, or merely 10% for high plug-in cases⁴. A separate Cenex press release states that if V2G is unable to access grid services, then smart charging gives you the upper range of that value¹⁴. The two figures are not reconciled, and the practical answer depends on whether grid services are accessible to the household.

Home batteries do not earn export revenue in the same way. Their return is avoided import cost: charging on a cheap overnight tariff and discharging when electricity is more expensive⁶. The Energy Saving Trust case study of a household with solar and an EV describes charging the EV and battery at night on a cheaper off-peak tariff, with excess energy exported to the grid¹⁵.

At network scale, Cenex estimates V2G could defer network upgrades of £5bn, or £180 per household¹⁶. Ofgem's case study projects that if 50% of 2030 EVs were V2G enabled, this would open up 22 TWh of flexible EV discharging capacity per year and provide around 16GW of daily flexible capacity to the grid⁵.

Costs compared: charger, battery and installation

The hardware cost gap has narrowed sharply since the first trials, and the projections point to further narrowing. At the beginning of the Sciurus project, buying a V2G unit would cost in the region of £15k, plus installation². By the end of the trial, the V2G hardware and installation cost was around £3,700 higher than a smart chargepoint³. Cenex's commercial viability work records the Indra unit retailing to end users at approximately £5,000 including installation in 2021², and a 2022 Cenex article refers to a V2G charger costing around £4,500 at that time¹⁷.

Home battery prices are installer-quoted and the documents in this comparison do not carry a published UK figure, so no range is given here. The relevant point for the comparison is that a home battery is a second asset on top of the car, whereas V2G is an upgrade to a charger the household may be buying anyway.

Which cars and chargers support V2G in the UK

V2G is still not widely available, with eligibility requirements such as having a compatible car, charger and smart meter⁷. Government guidance on registering energy devices states that a V2G enabled chargepoint is able to draw power to charge the vehicle and export the electricity from the car battery back to the home or the grid, and that this requires a bidirectional chargepoint and for the car to be V2G compatible¹⁸.

On the vehicle side, Uswitch lists the Nissan Leaf and Volkswagen ID Buzz as common V2G-ready vehicles⁷. In the Sciurus trial, the only type of compatible EV was a Nissan Leaf⁵. Cenex recorded four V2G charger models available in the UK through different suppliers in 2021, with new suppliers entering the market regularly².

Charger connectors follow the standard pattern for home charging: units are available either with a tethered Type 1 or Type 2 cable, which can be plugged straight into the car, or with a Type 2 socket for use with the vehicle's charging cable¹⁹. A bidirectional unit adds the export path on top of that.

The market context is that battery electric cars accounted for two in five, or 40.9%, of available models in 2026²⁰, and 84% of electric car drivers have access to home charging²¹. Home charging access is the precondition for both options in this comparison.

What the UK trials show: PAVE, Utrecht and the research so far

The UK evidence base is built on a small number of trials, and their results are the strongest material available on what V2G actually delivers. Ofgem's case study records that 330 V2G devices were installed across the UK during the project²². The V2G Britain feasibility study is part of the Vehicle-to-Grid competition⁴.

The Sciurus trial is the largest domestic V2G trial in Britain, and its headline finding is that customers could recover the majority of their household energy costs³. The trial also produced the cost data that anchors most later projections: the incremental hardware cost was around £3,700 at the end of the trial²³, and the V2G unit dropped to around £3,700 more than a comparable smart charger in hardware and installation²⁴.

Beyond Sciurus, the PAVE project is described as Europe's largest Vehicle-to-Grid pilot, with findings showing low public awareness of bidirectional charging and its potential²⁵. The Utrecht deployment, run by Hyundai and We Drive Solar, launched a V2G mobility service in the Cartesius district with 25 IONIQ 5 units scaling to 150 during 2022²⁶.

On battery life, the EV-elocity work found that V2G could extend the life of an EV battery by about 10%, around one extra year of use⁴. Uswitch reports that while there are concerns that frequent charging and discharging could shorten EV battery life, the impact should be relatively minimal within recommended guidelines⁷.

Which fits which household: a choice, not a winner

The two options suit different circumstances, and the deciding factors are whether the household already has an EV, how often that car is at home, and whether a battery is wanted for reasons other than arbitrage.

A household with an EV that sits on the drive for long periods, a smart meter, and a willingness to accept a narrow list of compatible cars and chargers is the natural V2G case. The V2G Britain modelling shows the returns concentrate in high plug-in rate archetypes and in constrained areas⁴. The Sciurus trial's compatible vehicle list was a single model⁵, which is the clearest illustration of how narrow the current fit is.

A household without an EV, or with a car that is usually away during the day, is the natural home battery case. The IAAS guide states a battery is most worthwhile if you want backup power, do not have full-retail export rates, or can access cheap overnight charging tariffs¹². The NEA describes the mechanism as charging during cheap-rate periods and using the electricity later when it is more expensive⁶.

There is a third consideration that applies to both: the design of the equipment. The Energy Systems Catapult notes that the focus of EV charging and V2G technology design is customer needs and cost, and that it will do just enough to meet grid-related regulations such as fault ride-through and high voltage and low voltage withstand²⁷. That is a statement about engineering priorities, not about reliability, but it explains why the feature set varies between units.

For a household weighing the two, the honest position is that V2G is a trial-stage technology with a narrow compatible vehicle list and a hardware premium that is projected to fall, while a home battery is a mature fixed installation with no vehicle dependency. Neither is a winner in the abstract.

What owning either means for energy independence

Both options reduce dependence on imported electricity at the margin, and both leave significant dependence in place.

A home battery shifts when grid electricity is bought, not whether it is bought. The Energy Saving Trust case study describes the pattern: charging the EV and battery at night on a cheaper off-peak tariff, with excess energy exported to the grid¹⁵. The household remains connected, remains on a supplier's tariff, and remains exposed to standing charges and to the difference between peak and off-peak rates. The Energy Systems Catapult's Living Lab data shows battery-equipped homes with lower total daily grid consumption across three seasons, but winter consumption rose in those homes, attributed to a suspected arbitrage pattern¹³.

V2G adds a second dependency: the car. The household cannot export when the car is away, and the compatible vehicle list is short⁷. It also adds a dependency on the charger maker and on whatever platform coordinates the discharge, which is a supplier or aggregator relationship rather than a purely domestic one.

Backup power is the one area where the two diverge most sharply. The Climate Change Committee states that when a building or home also has the functionality to operate independently from the grid, known as islanding, V2X can enable the vehicle to act as a backup power source in a power cut¹¹. Uswitch notes that V2H can provide backup power from an EV to a home during power outages and support off-grid setups, but that this is limited to certain EV models and compatible chargers⁷. A home battery with islanding capability provides the same function without the car being present.

The independence question therefore turns on what the household is trying to be independent of. A battery reduces dependence on peak grid pricing. V2G reduces dependence on peak grid pricing and adds an export income stream, at the cost of depending on the car, the charger and the aggregator being available and compatible.