How much does it cost to charge an electric car?

“How much does it cost to charge?” has a simple answer for any one charge — and a more useful answer per mile or kilometre, which is what lets you compare with a petrol or diesel car.

The cost of one charge

cost = battery size × change in charge level ÷ charging efficiency × price per kWh

• Battery size is the usable capacity in kilowatt-hours (kWh), listed in the car's specification.
• Change in charge level is how much you add, such as from 20% to 80%.
• Charging efficiency accounts for energy lost as heat in the charger and battery. Around 90% is typical for home charging.

A 60 kWh battery charged from 20% to 80% takes in 60 × 0.6 = 36 kWh. At 90% efficiency, 40 kWh is drawn from the grid. At 0.15 per kWh, that charge costs 6.00. The EV Charging Cost Calculator does this for your own battery, levels and price.

Cost per mile or kilometre

Running cost depends on how efficiently the car uses energy. Cars and their dashboards state this as miles per kWh, kWh per 100 miles or kWh per 100 km. Divide the consumption by the charging efficiency, then multiply by your electricity price.

A car that does 3.5 miles per kWh uses about 28.6 kWh per 100 miles. Divided by 0.9, that is about 31.7 kWh from the grid; at 0.15 per kWh, about 4.76 per 100 miles.

Comparing with petrol — two examples

These use illustrative prices, not current ones; put your own figures into the calculator.

• United States: the electric car above, charged at home at $0.15 per kWh, costs about $4.76 per 100 miles. A petrol car doing 30 mpg with fuel at $3.50 a gallon costs about $11.67 per 100 miles.
• United Kingdom: an electric car doing 4 miles per kWh, charged at home at 25p per kWh, costs about £6.94 per 100 miles. A petrol car doing 45 mpg with fuel at £1.40 a litre costs about £14.14 per 100 miles.

UK mpg figures look higher than US ones for the same car because a UK gallon is 4.546 litres and a US gallon 3.785. The calculator uses the correct gallon for the units you choose.

Why public rapid charging changes the picture

Rapid chargers on motorways and in town centres often cost several times more per kWh than home electricity. In the UK example, the same car charged entirely at 75p per kWh would cost about £20.83 per 100 miles — more than the petrol car. Most owners who charge mainly at home pay far less than that, which is why the share of public charging is one of the inputs: it usually decides whether an electric car is much cheaper to run or only slightly.

Cheaper home charging

• Time-of-use tariffs offer cheaper electricity overnight. Scheduling charging for those hours can cut the cost per mile substantially.
• Charge little and often. Topping up at home covers most daily driving without visiting a rapid charger.
• Follow the manufacturer's advice on charge levels. Many recommend charging to around 80% for daily use and to 100% only before long trips, depending on the battery type.

Why winter costs more

Cold batteries are less efficient and heating the cabin uses energy, so consumption often rises noticeably in winter. If you use your dashboard figure, take an average over a few months rather than a single week.

What the comparison leaves out

Fuel is only part of the cost of a car. Purchase price, insurance, maintenance, tax and resale value all differ between electric and petrol cars and between models. The calculator compares energy costs, which is the part that changes most with how you drive and where you charge.