Explained: Selling your EV battery power back to the grid

Here’s Carzone’s explainer of V2G charging and of how EV owners can sell their power back to the grid.

Up to now, electric car charging has been a one-way street with electricity flowing from the grid into car batteries where it’s stored to power the car when required. But what if there was another way? What if EV owners could sell the power from their stationary car batteries back to the grid and make a profit from doing it? That’s where Vehicle-to-Grid (V2G) technology could come in.

The idea is pretty simple. Most electric car owners charge their cars at night using cheaper night-time rates. This means that when the car is parked at home there’s a battery just sitting there holding quite a bit of electricity. If the vehicle were connected to a power outlet, V2G technology would allow electricity providers to siphon off some of that unused electricity in order to balance the grid during periods of high demand. In places where there’s plenty of renewable energy, electricity providers may still, to meet peak-time demand, have to boot up so-called “peaker” oil, coal or gas power plants that are at their most carbon-intensive during the spooling-up phase. Being able to tap into reserves of electricity stored in EV batteries, essentially like a large, decentralised power station of connected electric vehicles. would potentially reduce the strain on the grid during peak times and cut down on the need to activate peaker plants.

The energy companies would pay the EV owners for their electricity while the car owners recharged at night at cheaper rates, profiting from the difference. The use of smart meters and apps would allow the EV owners to decide when their car was available for V2G use and how much power could be taken, ensuring that there’s always enough juice left in the battery should they need to go anywhere.

That all sounds great in theory, but what about the reality of the situation?

Although other manufacturers such as Volkswagen and Hyundai are developing V2G-capable cars, thus far in Ireland only the Nissan Leaf, e-NV200 van and Mitsubishi Outlander plug-in hybrid have the technical ability for bi-directional charging thanks to their CHAdeMO charging technology. The Combined Charging System (CCS) set-up used by most other manufacturers doesn’t currently support bi-directional charging and CharIn, the body promoting CCS, has said that CCS likely won’t support V2G until 2025.

At present, although a number of places (notably Utrecht in the Netherlands) continue to run large-scale experimental V2G projects, there hasn’t been any mass roll-out of V2G technology as a strategy to support national electricity grids, despite the UK energy regulator, Ofgem, touting it as a proposal that could help Britain meet its future energy needs. The Netherlands has been a leader in V2G technology, having installed hundreds of bi-directional chargers across the country over the last two years, though its impact on the Dutch grid has, so far, been minimal.

Neither has there been any major discussion of V2G technology in Ireland, even with the announcement of new electric micro-generation grants; nor is there yet any way for electric car owners to sell their excess power to the grid. ESB Networks says that this capability may come “in time” and that the communication architecture required is “in development” but until it arrives that doesn’t necessarily mean that some of the other technology behind V2G won’t have its uses.

Some people with solar panels or other renewable energy sources already reuse battery packs from scrapped electric cars to store excess power to run their homes. By means of both smart meters and in-built V2G technology, until it becomes a realistic prospect to sell it to the grid, EV owners could potentially use the batteries of their own electric cars to store their excess solar- or wind-derived electric power for use in their home (known as Vehicle-to-Home or V2H charging). While it wouldn’t allow EV owners to make a profit, it would allow them to reduce their emissions and potentially make huge savings on their electricity bills, especially on sunny or windy days when they have power in abundance. Even for those without solar panels, charging an EV at cheaper night-time rates and using V2H technology to run showers and cookers during the day could also net huge savings for electricity customers. It could also mean that should the electricity grid in an area be knocked out due to a fault or storm, for those with V2H capability, the lights wouldn’t necessarily go out.

Although V2G may seem like an easy way for EV owners to make a little money on the side, there is as yet no guarantee that it won’t turn into a redundant technological dead-end as grids evolve in the next decades. Even if it doesn’t, for Irish EV owners at least, earning money from V2G is still some years away.