Vehicle to Grid (V2G)

Vehicle-to-grid technology moves energy out of the battery back into the grid. Drivers who supply energy to the grid through vehicle-to-grid technology are rewarded financially - they sell their energy to the grid.

Load and energy storage

Famously, the UK electricity grid feels strain at half-time in major televised football matches, because so many people switch kettles on in unison. It sounds like a quaint myth exploiting a British stereotype, but the National Grid recognise the phenomenon as "TV pickup" and have to prepare for it.

This trivia shows that electricity demand is not evenly distributed in time. Uneven load has always been a problem, but with the transition to renewable energy generation, the traditional solution of firing up more furnaces is becoming a less desirable option. (The uneven distribution of load throughout the week also explains why it is greener to charge your car and run appliances at night rather than during the day.)

Battery energy storage is a potential solution to this problem. When energy supply exceeds energy demand (usually during the night), it's better to save it in batteries rather than use it. Then when demand starts to exceed generation during spikes, some of the cover can come from batteries.

Engineers are working on developing the best battery technology to help give the grid a boost in these situations, but a mass of cars parked in driveways across the country could help supply some energy at peak times as well, as long as they are capable of dispensing energy back into the grid.

How it works

A quick reality check. Vehicle-to-grid technology is still developing in the UK. Octopus Energy claim that their Power Pack tariff, which launched in June 2025, is the only vehicle-to-grid tariff in the UK.

Only some cars are enabled with vehicle-to-grid technology, and only some chargers. The Octopus Power Pack only has four possible car-charger pairings, so it is necessary to meet one of these combinations to sell energy back to the grid.

Your energy supplier will put some requirements on you. In particular, you must plug in a minimum number of hours a day, and you must not require too much energy for your own mileage. You will also need to get permission from your local electricity distribution network operator to sell energy to the grid, like the process that those with solar panels follow to sell back to the grid.

Importantly, you set a minimum level of charge on your battery. There needs to be scope for the state of charge to move up and down, but you don't want to find you have sold all the energy in your battery when you need to go out! In the case of Octopus Power Pack, you can set this minimum state of charge anywhere from 0-30%.

Benefits to users

Because the car charges at a time when energy is abundant relative to demand, the resident is buying low. Because the car dispenses energy back into the grid when energy is scarce relative to demand, the resident is selling high. This means profit!

Home charging during off-peak hours is so much cheaper than at peak hours, that it could be that the profit made on vehicle-to-grid energy covers mileage, meaning free driving.

Drawbacks

Energy transfer into and out of the battery degrades the battery quicker. This will mean the battery has to be replaced sooner, at significant cost and carbon impact.