"How much does it cost to charge an electric car?" depends on where you charge, your tariff, and your car's efficiency. Here's the maths.
The formula
cost per charge = kWh added × price per kWh × (1 + losses) cost per mile = price per kWh × (1 + losses) ÷ miles per kWh
Charging losses are commonly in the high single digits to low teens as a percentage. I use 10% as a working figure. Your car's trip computer shows its efficiency in miles/kWh (or kWh/100 km).
Worked example
Illustrative inputs:
- Car efficiency: 3.5 miles/kWh (≈ 17.8 kWh/100 km)
- Losses: 10%
| Where | Price per kWh | Cost per mile | Cost per 1,000 miles |
|---|---|---|---|
| Home, standard tariff | 25p | 7.9p | £79 |
| Home, off-peak EV tariff | 8p | 2.5p | £25 |
| Public slow/destination | 45p | 14.1p | £141 |
| Public rapid | 75p | 23.6p | £236 |
The spread between off-peak home charging and rapid public charging can be huge, more than 9× in this example.
In kilometres and euros
cost per 100 km = kWh/100 km × price per kWh × 1.10
17.8 kWh/100 km × €0.30 × 1.10 ≈ €5.87 per 100 km.
Tips to cut charging costs
- Get a time-of-use or EV tariff and charge overnight.
- Use solar if you have panels, with smart chargers that follow solar output.
- Precondition while plugged in in winter.
- Save rapid charging for road trips.
- Check memberships: some networks offer cheaper rates with subscriptions.
My Electricity Cost calculator handles the kWh-to-cost part for any charger power and duration.