EV Charging Cost Calculator

Charging losses are the detail most calculators skip, and they are not trivial: you pay for the energy drawn from the wall, not the energy that reaches the battery. At 90% efficiency, a tenth of what you pay for becomes heat in the cable, charger and battery. Home AC charging typically runs 85–92%, and rapid DC charging is usually more efficient per kWh while costing far more per kWh. The other habit worth understanding is why rapid-charging stops end at 80%: the car deliberately tapers the power near the top to protect the cells, so the final 20% can take as long as the first 60% and is rarely worth the wait unless you need the range.

Energy into the battery = capacity × (target% − start%). Energy drawn from the supply = that figure ÷ charging efficiency. Cost = energy drawn × price per kWh. Charging time = energy into the battery ÷ charger power.

Real-world efficiency varies far more than this model can capture. Cold weather reduces both range and charging efficiency substantially, motorway speeds consume much more per mile than town driving, and rapid charging tapers sharply above about 80% so the last fifth takes disproportionately long. Tariffs also differ: overnight rates can be a fraction of the standard rate, while public rapid chargers often cost several times more.

A 75 kWh battery charged from 20% to 80% takes 45 kWh into the battery, but at 90% efficiency draws 50 kWh from the supply. At 0.28 per kWh that is 14.00, and roughly 6 hours on a 7.4 kW home charger.

1. Enter your battery capacity and the charge window.
2. Enter your electricity price per kWh.
3. Optionally add charger power, your car’s efficiency and petrol figures.
4. Read the cost, the time and the comparison.

• Ignoring charging losses and understating cost by roughly a tenth.
• Using summer efficiency figures to budget for winter driving.
• Assuming rapid charging costs the same as charging at home.
• Expecting the last 20% to charge as fast as the first 60%.

The EV Charging Cost Calculator works out what it costs to charge from one state of charge to another, including the energy lost as heat during charging. It can also estimate charging time, cost per mile or kilometre, and how that compares with running a petrol car.

EV owners tracking running costs, and anyone comparing an electric car against petrol before buying.

• Includes charging losses, which most calculators quietly ignore.
• Separates energy into the battery from energy drawn from the supply.
• Estimates charging time from your charger’s power.
• Direct cost-per-distance comparison against petrol.

• Working out what an overnight home charge costs.
• Comparing home charging against a rapid charger.
• Calculating cost per mile for expense claims.
• Deciding whether an EV would save you money.