How do we do the maths?

This is how we work out our miles per £ figures

Tom Barnard

22 Sep 2022

When comparing a petrol or diesel car’s efficiency, we are all pretty used to looking at the miles per gallon figure, even though we haven’t bought fuel by the gallon for quite a few years. We know that a big petrol SUV will struggle to get above 20mpg and will be costly to run, while a diesel or hybrid might manage 60mpg. Using that benchmark we know that the SUV will cost three times as much in fuel to cover the same distance.

For electric cars there are similar sorts of calculations because some EVs are far more efficient than others. The most generally-used is kWh per mile, but to make things simpler we have devised a miles per £ calculation which will give you an indication of how far you will be able to travel for a pound's worth of electricity.

To come up with this figure, we’ve assumed some things – which isn’t perfect and the actual figure you will achieve will depend on factors like how you drive and even the weather. But hopefully it will give you an indication of which cars make better use of your precious power.

To come up with the figure we take:

· The manufacturer’s stated battery size (say, 50kWh)

· The official range figure (say 200 miles)

· The UK average rate for domestic electricity (16p per kWh)

50kWh will therefore cost £8.00 to ‘fill up’ and it will carry you for 200 miles, which equals 25 miles per £. 

It’s not perfect, and the boffins will bleat about it – but it’s a good standard benchmark using like-for-like figures to give you an idea of which cars are efficient.  

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