Ian Featherstone Energy Saving Trust

Drives: Mazda 2

Energy Saving Trust is an independent organisation that works to address the climate emergency.

Is it better to swap a combustion engine car for an EV or to drive an existing car into the ground?

If your vehicle is near the end of its life, then there's no doubt that, if you can afford it, you should go for an EV. You'd probably be buying a used vehicle and there are growing numbers on the market. But if you have a car with several years of life left, the decision might centre on how far you drive each year.

The 2019 National Travel Survey stats show the average mileage for a privately owned car is 7,200 miles a year. If you drive fewer miles, there is an argument to keep the car. If more, the next owner is likely to drive fewer miles so it could be better to sell the car and do your miles in a vehicle without emissions.

If using a car for any sort of business activity, it's quite likely that an EV is going to be cheaper than a conventional car over the same period of time. However, there are other factors to consider, especially now we're looking at fuel prices of over 150p a litre. A car that does 45 miles to the gallon costs 15-16p a mile just to drive it, but there are some low overnight-electricity rates at between 4p and 7.5p a kilowatt hour, which equates to a couple of pence a mile. If you drive 10,000 miles or more a year, the difference is a lot of money.

Will economic, rather than environmental issues, be the catalyst for mass uptake of EVs?

A lot of people do want to do the right thing for the environment but are concerned about what it's going to cost. However, it may be a case of doing the sums and realising there’s a good chance of making savings.

Should there be concern about the environmental impact of mining lithium for batteries?

There are environmental concerns with any mining, so you have to compare it with the risks associated with mining oil and transporting it around the world.

The batteries themselves aren't going to end up in landfill as they're full of valuable materials and, in any case, legislation will require recyling. So although the process of recycling lithium-ion batteries isn't totally worked out, there's a lot of progress in that area. By the time there's any volume of batteries coming back, the materials will be recyclable.

People are concerned that batteries may only last four or five years, as in some laptops and phones, but vehicle manufacturers are putting eight-year warranties on these things and they're not expecting them to conk out the following day. It's likely the batteries will last as long as the vehicles, and then the whole car will be recycled – as diesel and petrol cars are now.

Advances are happening all the time to make the situation more sustainable.

Mukti is an environmental entrepreneur who has won awards in the areas of carbon calculation, and eco design and innovation.

Is it better to swap petrol and diesel for electric or is it more environmentally friendly to drive existing cars into the ground?

It depends how many miles you drive each year. If you do a lot it's worth switching now. If you do hardly any miles, you'd be better to wait.

To understand why, you need to look at a comparison between a medium-sized petrol car and a medium-sized electric car. The embodied carbon (the CO2 emitted to create it) for a medium-sized petrol car is about 5.3 tonnes. Electric cars have more embodied carbon because they are more high-tech and their battery manufacture has higher emissions, so the embodied carbon for manufacturing a medium-sized electric car is around 11.2 tonnes.

However, the electric car has much lower emissions per mile. It does have some emissions because producing electricity on the grid is only partly from renewables.

Driving 10,000 miles a year in a petrol car would emit 2,790 kilos of CO2, but an electric car would emit just 520 kilos of CO2. That's a saving of around 2.27 tonnes of CO2 per year from the fuel. So if you drive around 10,000 miles a year and you swap your medium-sized petrol car for a medium-sized electric car, it would take 2.6 years to pay off the additional embodied carbon from the manufacture of the new EV. After that time period you'd have a lower carbon footprint.

If you drive an average of 20,000 miles a year it would only take 1.3 years to reach a lower carbon footprint. These calculations assume you charge your electric car at home half the time and that you are on a renewable electricity tariff.

Of course it depends on your own finances and personal preferences. If you can't afford to switch to electric immediately, reduce your mileage in your petrol car and you’ll have nearly as much effect.

One of the best ways to do this is to buy an electric bicycle and use it for your short journeys. They have a tiny fraction of the embodied energy of cars because they weigh around 100 times less. And they cost just .03p per mile to run, with carbon emissions per mile of around 5g (compared to 300g per mile for a mediumsized petrol car). Plus you get all the benefits of cycling and being outdoors.