What this answers
What does it cost to charge the car, and is it cheaper than petrol? The calculator takes the battery size, what the car uses per 100 km, your electricity price and the loss in charging, and gives the cost of a full charge, of 100 km and of a month, next to the same distance in a petrol car.
Formula
Energy drawn = battery / (1 − loss)
Cost per 100 km = consumption / (1 − loss) × price per kWh
Saving per month = petrol cost − electric cost, over the monthly distance
- loss — the share of the energy drawn from the socket that is lost as heat and never reaches the battery
Worked example
A 60 kWh battery at 10% loss draws 60 / 0.9 = 66.7 kWh from the socket. At 0.20 per kWh a full charge costs 13.33. A car using 18 kWh/100 km draws 18 / 0.9 = 20 kWh for 100 km: 4.00. A petrol car at 7 l/100 km and 2.00 a litre pays 14.00 for the same 100 km. Over 1,000 km a month that is 40 against 140, a saving of 100 a month.
The numbers you fill in yourself
The price per kWh depends on your contract, the hour and the charger, so the field opens on a round number meant to be replaced. The same goes for consumption, loss and the petrol car.
What is not included
Purchase price, tax, servicing, insurance and charging subscriptions. One price for all charging: home and fast charging at different prices are two calculations. Consumption is held constant, which cold weather and speed do not allow.