Two-way electric vehicle charging at scale could stop renewable energy being wasted – here’s how it works

The amount of renewable energy produced around the world is increasingly exceeding demand – particularly from wind and solar sources. This presents a significant challenge when limited grid capacity and insufficient energy storage mean this clean power has to be curtailed, wasting the excess generation. The scale of this problem is substantial.

In the UK, for example, wind farms were forced to curtail 4.3 terawatt (trillion watt) hours of surplus energy – about 5% of their annual output – in 2023. This would have been enough to power 1.5 million homes for the year, so failing to harness it cost bill payers roughly £300 million and left some energy providers facing costly constraint payments.

Similar patterns are emerging across Europe, North America, Australia and other regions rapidly expanding their renewable capacity, where grid infrastructure has struggled to keep pace.

But on the Isle of Wight, off England’s south coast, a trial is under way that, in years to come, could help resolve this energy conundrum. It relies on “bidirectional charging” – the idea that electric cars don’t just have to be energy users; they can be energy storers and providers too.

By 2040, around 36 million electric cars and vans are expected on UK roads. Already, current models can store enough energy to power a typical UK household for between seven and ten days. All the anticipated electric vehicle (EV) batteries by 2040 would offer around 2.5 terawatt hours of storage – enough to store much of the UK’s surplus solar power generated at bright summer lunchtimes, or the excess wind on stormy winter nights.

For most of the time, of course, (about 95%, on average), these cars won’t be using any of that energy because they are parked. Our technology could put this EV downtime to use storing and recirculating surplus renewable energy.

EV owners won’t just be doing this out of the goodness of their hearts. It would also mean they could buy electricity at cheaper, off‑peak times, then store it for their own household use in peak times. A new study from the University of Michigan finds that vehicle‑to‑home (V2H) charging could save drivers up to US$5,600 (£4,200) over their EV’s lifetime – as much as 90% of its total charging costs.

Energy companies and grid operators also stand to gain. One analysis estimates that European power systems could save up to €4 billion (£3.5 billion) through the introduction of vehicle-to-grid (V2G) and other smart‑charging schemes.

Two-way technology

Most EVs and chargers currently only move electricity one way – from source to car. But at the Centre for Self-Sustaining Systems and Societies, our focus is on two-way technology that enables energy to flow between EVs and homes, hotels, businesses, as well as the National Grid itself. This is complicated technology – not least because the form of electricity in which batteries store electricity, direct current (DC), needs converting into alternating current (AC) before it can be pumped back into a home, hotel or grid.

EVs will also need adapting to support bidirectional charging – currently, only a few models offer this capability. Widespread adoption will require all EVs to be factory-designed with integrated bidirectional hardware, supported by clear regulatory standards and strong market incentives.

On the Isle of Wight, our technology – part of the Europe-wide DriVe2X programme – is testing four bidirectional chargers at two hotels and a visitor boat mooring. One reason the Isle of Wight was selected for this test is its annual influx of tourists.

The island attracts more than 2 million visitors each year, meaning there are major fluctuations in demand for power between its low and peak tourism seasons. But many visitors bring EVs with them, and these could potentially store and circulate some of the extra power the island requires during their stay.

Our test drivers (a mixture of visitors and local residents) are able to schedule their departure times and minimum battery levels, so that our bidirectional charging system can store and circulate energy while retaining enough charge for the EV’s next trip. This addresses a fear that is sometimes expressed about this new technology – the risk of discovering a flat-battery just as you wish to set off on your journey.

The trial, which is moving into its final stage, has been given a community-first mindset through our local partner Future Isle of Wight, a community-owned company that is helping to shape how this technology can be scaled in a way that benefits local residents.

Across Europe, other DriVe2X test sites are exploring potential two-way energy hotspots. At Porto Airport in Maia, Portugal, a long-stay car park is testing how this technology can manage waves of passengers flowing in and out of an airport terminal. In Hungary’s capital Budapest, vehicle-to-home technology is being tested in a number of smart homes.

While there are now more than 100 V2G test projects around the world, they remain small in scale. Key challenges include developing affordable smart chargers and hassle-free grid connection regulations, as well as protecting consumer confidence on issues such as battery warranties, privacy, and fair payment for the power their EVs provide.

Nonetheless, I believe bidirectional EVs could move from niche pilots to everyday life within the next two decades. In July, the UK government suggested that households and businesses could be providing the country with up to 75 gigawatts of flexible power by 2050 – of which more than half (40 gigawatts) would come from EVs. That is roughly the output of 40 large nuclear reactors – enough to power Britain’s total electricity consumption during a peak winter period.

But this future depends on daily life working smoothly. EV drivers will need to wake up with enough charge, understand when their vehicle is powering the house, and see they are saving money – all without worrying about battery wear, confusing markets or privacy risks. We hope our Isle of Wight trial can play a small but important role in realising this energy-efficient future.

Vahid Vahidinasab receives funding for the DriVe2X research and innovation project, which is co-funded by the European Commission and UKRI under grant numbers 101056934 and 10055673, respectively.