EV Charging Cost Calculator

How to use the ev charging cost calculator

1. Fill in the fields — they start with a worked example.
2. Read the answer, and the arithmetic shown beneath it.
3. Copy the results, or adjust the inputs to compare scenarios.

About this tool

Charging cost is battery capacity multiplied by your electricity rate, adjusted for the energy that never reaches the battery. That last part is the piece most calculations leave out, and it is not small.

Charging is lossy. Energy is lost as heat in the cable, the onboard charger and the battery itself, so the meter records more than the battery gains. Home AC charging typically runs at 85 to 90 per cent efficiency; rapid DC charging is often worse, and cold weather makes both worse again because the car spends energy warming the pack before it can accept a fast charge.

The gap between home and public charging is usually far larger than the efficiency difference, though. Home electricity might be a quarter of the price of a rapid charger, which is why the cost per mile shown here changes so sharply with the rate you enter.

Efficiency in miles per kWh is the figure worth knowing about your own car. Manufacturer numbers assume mild weather and gentle driving; motorway speeds and winter heating both reduce it substantially, sometimes by a third.

Common uses

• Comparing home charging against public rapid charging.
• Working out cost per mile against a petrol car.
• Estimating the cost of a long trip.

Frequently asked questions

Why is the cost higher than battery size times rate?

Charging loses energy as heat, so the meter records more than the battery receives. Home charging is typically 85 to 90 per cent efficient, and rapid charging often less.

How many miles per kWh should I expect?

Roughly 3 to 4 for most cars in mild conditions. Motorway speeds and winter heating can cut that by a third, so use your own observed figure if you have one.

Is rapid charging much more expensive?

Usually far more than the efficiency difference alone — public rapid rates are often several times a home tariff, which is why the rate matters more than anything else here.