Speaking at the RAC Foundation’s Shades of Green event, Imperial’s Dr Ricardo Martinez-Botas said although EVs are more energy efficient, equivalent CO2 emissions for well-to-wheel were actually higher than hybrids because of the way electricity is generated in the UK.

The study looked at 50 vehicles, including conventional petrol and diesel cars, hybrids, EVs and fuel cell vehicles. It showed that, based on the average emissions of the UK grid, the 16 EVs on test averaged equivalent to 105g/km CO2, compared to 103g/km for the 20 hybrids.

Emissions for EVs also vary heavily depending when the cars are charged. Night time charging, where a large percentage of electricity comes from nuclear stations, reduced this figure to 80g/km for the EVs tested.

Charged during the day, the same cars would be emitting equivalent to 118g/km CO2 – almost 50% more than night time charging due to the wider use of fossil fuel stations during peak demand.

However, Dr Martinez-Botas also pointed out that with zero tailpipe emissions, electric vehicles were a solution for improving air quality in cities.

It raises questions for companies offering charging points for employees to top up batteries during work hours. For the most environmentally friendly and fleet, night time charging