How much does an electric car cost per mile?

Two years of volatile energy prices have shone a spotlight on the cost of electric vehicle charging, and efficiency is becoming an important differentiator. Improved efficiency can extend a vehicle’s range without adding a heavier, more expensive battery, and contributes to lower per-mile fuel costs too.

The cost of charging is just as variable as filling with fuel. Electricity is measured and sold by the kilowatt-hour (kWh), similar to buying liquid fuel by the litre. Just like a larger fuel tank, the more kilowatt-hours of energy a vehicle’s battery can store, the further it’ll travel on a full charge, and the more it’ll cost to fill up.

However, the cost to fully charge doesn’t tell you much. Per-mile fuel costs depend on your vehicle’s efficiency and where you choose to plug it in – and the good news is, it’s still often cheaper to drive an electric car than a fuelled one. Here’s what you need to know.

It depends. Since 2017, vehicle efficiency has been calculated using the Worldwide Harmonised Light Vehicle Test Procedure (WLTP). It’s a laboratory test which includes four cycles simulating different road types, and vehicles are fully charged before and afterwards to measure the energy used.

Efficiency is presented as a weighted ‘combined’ average, but manufacturers haven’t settled on a standard unit yet. Some publish figures as watt-hours per kilometre (Wh/km), others use in kilowatt-hours per 100 kilometres (kWh/100km) or miles per kilowatt-hour (MPkWh).

As UK roads are measured by the mile, MPkWh is perhaps the most relatable of those figures. It’s also easy to calculate:

• Divide the Wh/km figure by 10 to convert it to kWh/100km (if necessary)
• Divide the result by 62 to get kWh/mile (100km is 62 miles)
• Divide 1 by that result to get a figure in MPkWh

• 162 / 10 = 16.2kWh/100km
• 6.2 / 62 = 0.261kWh/mile
• 1 / 0.261 = 3.8MPkWh

Although real-world efficiency will depend on your driving style, WLTP is a useful way to compare vehicles because it includes energy lost as heat while charging – similar to spilling fuel while filling up, you’ll pay for that even if it isn’t used to charge the car. This also means WLTP figures aren’t comparable with your trip computer – as those only measure how much energy from the battery has made it to the wheels.

Dividing your vehicle’s range by its battery capacity can also give you an indication of its efficiency. However, some manufacturers publish the gross capacity – this includes a portion that cannot be charged or discharged, so doesn’t contribute to your range or charging costs, and the size of that buffer varies between models. An Audi Q4 40 e-tron can use 76.6kWh (93%) of its 82kWh battery, whereas the MG4 Standard Range uses 50.8kWh (99.6%) of its 51kWh pack, due to a very different cell chemistry.

To work out the per-mile electricity cost, divide the price of the electricity (pence per kWh) by the distance it will take you (MPkWh).

Figures for a selection of popular electric vehicles in the UK (according to DfT data) are provided below. Calculations are based on the latest Ofgem-capped electricity prices and Economy 7 tariffs from Octopus Energy.

The same calculation applies at public chargepoints, buts the costs are often significantly higher – especially at the fastest DC rapid chargers.

For example, the Tesla Model Y Long Range – the UK’s best-selling electric car – would cost 3.3p per mile charged overnight at home on an Economy 7 tariff, or 19.8p on most of the UK’s largest rapid charging networks.

HM Revenue and Customs (HMRC) issues Advisory Fuel Rates (AFRs) for travel reimbursement, based on combined cycle economy data for fleet-registered vehicles and fuel prices from The AA.

The latest rates suggest electric vehicles are two to four times cheaper per mile than their petrol or diesel equivalents if they are charged at home, and only slightly more expensive if when plugged into a rapid charger. Drivers should be able to balance out the cost of using more expensive public chargepoints if they’re doing most charging at home.

There is also an Advisory Electric Rate (AER) for electric vehicles – it’s a flat rate of 9p per mile, regardless of efficiency.

Still confused? The LeasePlan calculator can quickly work out how much your electric vehicle is costing to charge, including adjusting it to match your real-world efficiency and energy tariff.