What is vehicle-to-grid and will it revolutionise energy and EV charging?

Vehicle-to-grid is often described as the successor to “smart charging”. Could it herald a new era for energy use or is it a niche service? Read this guide on vehicle-to-grid, or V2G, to find out.

There’s been lots of chatter about vehicle to grid (V2G). Firstly, it sounds cool – “My car and charge point has V2G capability, don’t you know.” And secondly, it could form part of the solution to balancing supply and demand in the grid.

Perhaps not that cool then, but the acronym is thrown around a lot in EV circles and it promises to be very useful indeed. The National Grid is interested in the concept as it could help it balance the energy demand and supply in the grid; EV drivers like the idea they could sell energy back to the grid/suppliers; and energy suppliers have cottoned on to this fact, so a number of them are making sure they’re involved in the early stages before the tech bypasses them completely.

But what exactly is V2G, what can it do and what does it mean for you? We asked Daniel Hollingworth, UK Manager at Ohme, to explain.

What is “V2G”?

We all know electric cars have big batteries and we use the mains electricity supplied to our homes to charge them up. V2G (Vehicle-to-Grid) is a way of doing the opposite – using the stored energy in the battery to feed back into the house. A typical electric car battery can store enough energy to supply the whole house with electricity for a few days. V2G is also of interest in commercial locations too, such as offices and car parks – anywhere where a car could be plugged in for a few hours.

How does V2G work?

The first thing to mention is that a car battery is DC (Direct Current) and our mains electricity is AC (Alternating Current). A special charger is needed for V2G that can convert the car battery’s DC to AC and then synchronise it to the 50Hz cycles of the electricity system. A V2G charger also needs a control system and user input so it knows when to charge and when to discharge the battery.

Why is V2G useful?

V2G can be used to save money and even make money for the owner. For example, it can be used to soak up excess solar generation during the day and then feed it back into the house in the evening, therefore reducing electricity bills.

It can also be used to support National Grid and the Electricity Network Operators when electricity demand is higher than expected or where the wires of our networks are struggling to transfer enough electricity to an area. There are markets that are starting to emerge whereby drivers with V2G can be paid to feed energy into the grid when a signal is sent to the charger.

Can all cars make use of V2G?

At the moment only Nissan electric cars and vans support V2G, using the CHAdeMO rapid charging connector. It is not yet available through the CCS connector, although it’s likely this will change in the future.

EV Basics - types of EV charging stations and connections

Is V2G ready yet?

There have been several large trials, supported by government funding, to test V2G chargers in the “real-world” at scale. (See https://es.catapult.org.uk/case-studies/vehicle-to-grid-britain/ for more information.)

The charging technology is fairly straightforward, but a bigger challenge is developing the overall control system that drivers can use easily. A car’s principal purpose is transport, so it is vital that V2G systems interact with drivers to make sure their car is charged when they need it to be (editor’s note: instead of drivers finding their EV battery unexpectedly lower than they needed).

In terms of cost, at the moment V2G chargers are prohibitively expensive for most people outside of trial-funded projects. It will be a changing picture though - V2G charger costs may come down and potential revenue from the electricity system may go up, so it’s possible they could be a mainstream option, but probably not for at least five years.

Do we need V2G to make the EV transition possible for everyone? Can the grid cope without it?

It’s important to note that the UK’s electricity system has enough overall capacity to support EVs – just not necessarily charging at the peak times. This is backed up by many statements from the National Grid and most notably its Future Energy Scenarios reports.

Smart charging – the ability to intelligently charge at the right time – is the most important technology to enable mass adoption of EVs. This is why it has been heavily supported by government by introducing smart charging in legislation.

V2G can have a place in providing the needed flexibility in our energy system, alongside many other solutions, but it is more likely to be a technology choice for those wishing to make a higher initial investment and earn additional revenue to recoup it back over a longer period of time.

Is it possible to trial V2G?

Yes. There are a number of V2G trial projects being run. Octopus Energy offer their PowerLoop deal, where you can get a deal which includes a Nissan Leaf, the V2G charger and cashback incentives for using the system.

(Editor's note: Electric Nation is also running a V2G trial. Spaces are limited. More information here)