Miles per kWh is the electric car's version of miles per gallon, and it is the single number that decides what your motoring costs. Most cars sit somewhere between 3 and 4 miles for every kilowatt-hour, with an average of around 3.5, but the spread is wide and the conditions you drive in move it about far more than people expect. This guide explains what the figure means, what real cars actually return, and how to find your own.
The short answer. A typical electric car returns about 3 to 4 miles per kWh, averaging roughly 3.5. Small, light, aerodynamic cars manage 4 to 4.5 or better; large SUVs and performance models drop to 2.5 to 3. Cold weather, motorway speeds, a heavy load and hard acceleration all cut the figure, sometimes by a third in deep winter. Your cost per mile is simply your electricity unit rate divided by your miles per kWh.
What miles per kWh actually means
A kilowatt-hour is a unit of energy, the same unit your electricity bill is priced in. Miles per kWh tells you how far the car travels on one of those units, so a car doing 3.5 miles per kWh covers three and a half miles for each unit it draws from the battery. It is the mirror image of the energy figure carmakers sometimes quote the other way round, in watt-hours per mile or per kilometre, where a lower number is better. Miles per kWh is the friendlier way to think about it for everyday sums, because it slots straight into a cost calculation: take what you pay per unit, divide by your miles per kWh, and you have your cost per mile. On a cheap overnight rate that lands around 2p a mile, which is the figure that makes an electric car so cheap to run, as the cost of charging at home guide sets out in full.
What real cars return
Manufacturer figures from the official test tend to flatter real driving, much as the old mpg figures did, so it is worth working from real-world numbers. As a rough guide, efficiency tracks the size, weight and shape of the car. A small, light, slippery hatchback is the most efficient thing on the road; a tall, heavy SUV or a fast performance car pushes more air aside and carries more mass, so it uses more energy for the same distance.
| Type of car | Typical miles per kWh | Cost per mile off-peak (8p) | Range from 60 kWh |
|---|---|---|---|
| Small, efficient EV | 4.0 to 4.5 | 1.8p to 2.0p | 240 to 270 mi |
| Mid-size hatch or saloon | 3.3 to 3.8 | 2.1p to 2.4p | 200 to 230 mi |
| Large SUV or performance EV | 2.5 to 3.0 | 2.7p to 3.2p | 150 to 180 mi |
| Rough average across all | 3.5 | 2.3p | 210 mi |
Cost per mile worked at an example 8p off-peak EV rate; multiply through for your own rate (for instance at the 26p standard rate the figures are roughly three times higher). Range assumes a usable 60 kWh battery. These are mild-weather, mixed-driving figures; winter and motorway use sit lower.
What drags the figure down
The number on a spec sheet is a best case, and four things in particular pull your real efficiency below it. Cold is the largest. In winter the battery is less willing to give up its energy, and far more importantly the car has to heat the cabin from the battery rather than from waste engine heat as a petrol car does, so short cold trips can knock 20 to 30 per cent off your miles per kWh. The EV charging in winter guide goes into this in detail. Speed is the next: air resistance climbs steeply with speed, so a steady motorway cruise uses noticeably more energy per mile than town driving, which is the reverse of what people expect from a petrol car. Town driving actually suits an EV, because regenerative braking claws back energy every time you slow down. Weight and load matter too, so a full car, a roof box or a towed trailer all cost range. And a heavy right foot, with hard acceleration and high speeds, drains the battery far faster than a gentle, anticipatory style.
Why town driving beats the motorway
This catches a lot of new EV drivers out. In a petrol car, stop-start town driving is the thirsty bit and a steady motorway run is where you see your best economy. An electric car flips that. Regenerative braking means that much of the energy you would lose slowing for a junction is recovered back into the battery, so urban driving, full of gentle slowing and stopping, is where an EV is most efficient. The motorway, where you hold a high steady speed against rising air resistance and rarely brake, is where efficiency is worst. It is why a long fast journey eats range faster than the same miles around town, and why easing off the motorway speed is the single most effective thing you can do to stretch a charge on a long trip.
How to measure your own
You do not have to guess, because every electric car tracks this for you. The dashboard or the trip computer shows a lifetime and a recent average efficiency, usually in miles per kWh or watt-hours per mile, and watching it over a few weeks tells you your real figure far better than any published number. If you want to check it independently, note the odometer and the energy used between two full charges, or simply divide the miles you covered on a charge by the kWh you put back in. Knowing your own figure is what makes the cost sums real: drop it into the running cost calculator alongside your unit rate, or just divide your rate by your miles per kWh, and you have your true cost per mile rather than an average that may not match how or where you drive.
Why this number matters
Miles per kWh is the hinge between two things you do control, your tariff and your driving style, and the thing you care about, the cost of every mile. A more efficient car needs less energy for the same journey, so it costs less to run and goes further on a charge, but the conditions you drive in swing the figure enough that the same car can feel cheap in summer and thirsty in a cold snap. Pair a good real-world efficiency with a cheap overnight rate and the right charging habits, covered in the best time to charge guide, and you reach the couple-of-pence-a-mile figure that no petrol car can match. The car matters, but as ever the tariff and the timing matter more.
The bottom line
Most electric cars return between 3 and 4 miles per kWh, around 3.5 on average, with small efficient cars doing better and large or fast ones worse. Cold weather, high speeds, heavy loads and hard driving all cut the figure, while gentle town driving and regenerative braking lift it. Watch your own car's readout for your true number, divide your unit rate by it for your cost per mile, and you will know exactly what your motoring costs rather than relying on a showroom figure.