How this calculator works
The charging cost comes from the energy drawn at the meter or charging network, not just energy stored in the battery. Battery energy equals usable capacity multiplied by the percentage-point increase. We divide by the charging efficiency you enter, then apply the tariff and any fixed session fee.
Example: a 60 kWh battery charged from 20% to 80% stores 36 kWh. At 90% efficiency the supply delivers 40 kWh, which costs £12 at 30p/kWh before connection fees.
Reference: Official guidance / methodology. External rates can change.
Common questions
Is charging at home always cheaper?
Not necessarily. Overnight tariffs may be cheaper, but public prices, standing charges, and your available tariff determine the comparison. Enter your actual pence-per-kWh rate.
Why is energy bought greater than energy added?
Electricity is lost as heat and in conversion. The efficiency field lets you estimate those losses without pretending one percentage suits every vehicle.