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By David Lewis, Electric Vehicle & Clean Energy Journalist.
When you get a petrol or diesel car, you want to know how many miles per gallon it does. The higher the MPG figure, the less money you have to spend on fuel.
So what’s the equivalent of MPG for an all-electric car? Instead of miles per gallon, it’s "miles per kWh" (pronounced kilowatt-hour).
In this quick jargon-busting guide, we explain everything you need to know about this new efficiency metric for electric cars.
With a traditional car, the miles per gallon, or MPG number, tells you how many miles the car will go on 1 gallon of petrol or diesel.
In an electric car, the miles per kWh figure tells you how many miles the car will go on 1 kWh, or unit, of electricity.
So, if your EV has a battery size of 50 kWh and an efficiency rating of 3 miles per kWh, then on average it can travel 150 miles on a fully charged battery (50 kWh x 3 miles per kWh).
What if you can't find the miles per kWh figure? Just take the battery range of the car and divide by the battery size. So an EV with a 240 mile range and a battery capacity of 60 kWh would have an efficiency rating of 4 miles per kWh (240 ÷ 60).
Note: In your calculations, you should – where possible – work with the "usable" or "net" battery size, not the "nominal" or "gross" battery size. Your battery's usable size / capacity is what the car can actually access.
Also, for your EV's battery range, you may need to use the official WLTP range figure at first, but it will probably give you a more optimistic miles per kWh result.
As you get to know your car over time and work out the real-world range (usually less than the official range), you can carry out the miles per kWh calculation again with both the usable battery capacity and the real-world range to get a very accurate miles per kWh figure.
Now we all know that 50 MPG is a pretty good efficiency rating for a normal car and that 15 MPG would be poor. But what about electric cars? What’s a high number and what’s a low number?
The highest efficiency electric cars today achieve 4 miles per kWh or above. Some are close to 5 miles per kWh.
For example, the standard range, rear-wheel-drive version of the Tesla Model 3 has an official efficiency rating of 4.8 miles per kWh.
A very low efficiency figure would be 2 miles per kWh. Some of the early electric cars that came out 8-10 years ago weren’t great at converting stored battery energy into actual miles driven.
Nowadays, most electric cars have an official efficiency of above 3 miles per kWh, though real-world efficiencies will generally be lower.
Having a high miles per kWh rating is all about saving money.
Imagine your EV can do 4 miles per kWh and you drive 8,000 miles a year. How much electricity do you need to cover that distance?
It’s 8,000 miles divided by 4 miles per kWh which equals 2,000 kWh (or 2,000 units of electricity).
If you charge at home on an off-peak tariff of say 7.5p per kWh, those 2,000 kWh will cost you £150 (2,000 kWh x 7.5p).
Now compare that with a car that can do only 3.2 miles per kWh. You’ll need more electricity to cover the same 8,000 miles. The calculation is: 8,000 miles divided by 3.2 miles per kWh = 2,500 kWh.
Charging at home at a rate of 7.5p per kWh would therefore cost you £187.50 (2,500 kWh x 7.5p). In the less efficient 3.2 miles per kWh car, you end up paying 25% more on electricity to go 8,000 miles.
In absolute terms, it’s only £37.50 extra a year, so still very good value when compared to a petrol or diesel car.
Want to discuss leasing an electric car?
Why not phone us on 0118 920 5130 or email at enquiries@selectcarleasing.co.uk
There’s a handy way of quickly comparing how efficient electric cars are compared to traditional petrol / diesel cars.
Just take the miles per kWh figure and multiply by 40. So an efficient 4 miles per kWh electric car is roughly the equivalent of a 160 MPG petrol or diesel car.
Even a relatively inefficient electric car offering 2.5 miles per kWh would be the equivalent of 100 MPG in a traditional car.
The ‘multiply by 40’ rule of thumb gives you a quick, approximate equivalent for electric vehicles in the UK. It won’t yield exactly the right figure, as there are many variables in play, but can give you a general indication of how efficient all-electric cars are compared to petrol and diesel powered vehicles.
Here is a selection of highly efficient electric cars you can lease from Select Car Leasing from a variety of manufacturers*:
| Make & Model | Efficiency Rating |
| 1. Dacia Spring Expression 70 24 kWh | 5.0 miles per kWh |
| 2. Tesla Model 3 Standard Range RWD | 4.8 miles per kWh |
| 3. Mini Cooper E Classic 41 kWh | 4.5 miles per kWh |
| 4. Peugeot E-208 Allure 51 kWh | 4.5 miles per kWh |
| 5. Citroen e-C4 X Max 54 kWh | 4.4 miles per kWh |
| 6. Hyundai Inster 01 42 kWh | 4.3 miles per kWh |
| 7. Fiat 500e Icon 42 kWh | 4.3 miles per kWh |
| 8. BMW i4 eDrive35 Sport 70 kWh | 4.2 miles per kWh |
| 9. Renault 5 E-Tech 52 kWh | 4.1 miles per kWh |
| 10. Vauxhall Corsa Electric Yes 50 kWh | 4.0 miles per kWh |
* Vehicles listed show their official miles per kWh figures.
Now you're up to speed on 'miles per kWh', why not take a look at more of our handy EV Guides and the latest Electric & Hybrid lease deals below:
Note sure what to look out for when considering an electric car? Read our simple 5-step guide covering vehicle types, official and real-world range, charging implications, savings potential, battery and electric motor performance, and more.
Do you have range anxiety? Worried you might not reach your destination in an all-electric car before the battery runs flat? In this detailed guide, we explain the difference between WLTP and real-world range, how to extend range, etc.
To support our fantastic EV lease deals, we have a wide-ranging set of guides to answer all your electric questions. We cover topics like range, charging, what are BEVs, PHEVs and HEVs, electrifying your fleet, and much more.
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