How much does it cost to charge an EV at home?
Battery capacity alone does not tell you what a charging session costs. You need the percentage added, the electricity rate and an allowance for charging losses between the wall and the battery.
The useful calculation
Worked example: 64 kWh battery, 20% to 80%
The battery gains 60% of 64 kWh, which is 38.4 kWh. If overall charging efficiency is 90%, the wall supplies about 42.7 kWh.
| Electricity rate | Wall energy | Session cost |
|---|---|---|
| 7p/kWh | 42.7 kWh | £2.99 |
| 15p/kWh | 42.7 kWh | £6.40 |
| 25p/kWh | 42.7 kWh | £10.67 |
| 35p/kWh | 42.7 kWh | £14.93 |
Cost per 100 miles at different charging prices
This example assumes 3.5 miles/kWh at the battery and 90% charging efficiency. Change both inputs for your own vehicle and conditions.
| Rate | Wall energy / 100 miles | Energy cost / 100 miles |
|---|---|---|
| 7p/kWh | 31.7 kWh | £2.22 |
| 15p/kWh | 31.7 kWh | £4.76 |
| 25p/kWh | 31.7 kWh | £7.94 |
| 35p/kWh | 31.7 kWh | £11.11 |
| 50p/kWh | 31.7 kWh | £15.87 |
| 65p/kWh | 31.7 kWh | £20.63 |
| 80p/kWh | 31.7 kWh | £25.40 |
Why your bill will not exactly match a battery-percentage calculation
Battery percentage is a vehicle estimate, not a calibrated electricity meter. Charging losses vary with equipment, temperature, battery conditioning and charging power. Some vehicles also use energy for preconditioning while plugged in. For a precise household-energy figure, a charger or smart-meter reading is stronger evidence than a generic efficiency assumption.
Cheap overnight rate does not automatically mean cheap household tariff
An EV tariff can reduce charging cost while increasing the rate paid for daytime household electricity. Compare the whole annual household bill, standing charges and the share of charging you can genuinely move into the cheap window.
Partial charging is normally the relevant calculation
Most charging sessions are not 0–100%. If you arrive home at 42% and leave at 80%, the battery receives 38 percentage points of its usable capacity, not the whole battery capacity. On a 64 kWh battery that is 24.32 kWh into the battery before losses. This is why multiplying the full battery size by the tariff can overstate an everyday session.
If your vehicle lets you set a charge limit, use the start and target percentages that match the actual session. For a regular overnight budget, it can be more useful to work from annual miles and mi/kWh than to assume a fixed number of full charges per month.