EV Charging Time and Cost Calculator with DC Slowdown

How to use it

Enter the Usable battery capacity from the car's specification, and the Charge at the start and Target charge in per cent.
Choose the Charger type, then the charger power in the list that appears.
Set the Charging efficiency, the Electricity price per kWh and the Consumption of the car in kWh per 100 km.
Read the Charging time, the Electricity cost and the Range added. The table shows the charge at every 5 per cent.

How the charging time is calculated

The energy that goes into the battery is its capacity times the change in charge. The charger delivers its power times the efficiency: a 150 kW charger at 90 per cent efficiency puts 135 kW into the battery. The time is the energy divided by that power.

Energy to battery (kWh) = capacity × (target − start) ÷ 100
Grid energy (kWh) = energy to battery ÷ efficiency
Time (hours) = energy to battery ÷ (charger kW × efficiency)
Cost = grid energy × price per kWh
Range (km) = energy to battery × 100 ÷ consumption (kWh per 100 km)

Why DC charging slows above 80 per cent

The US Department of Energy describes the same effect: at about 80 per cent state of charge the DC charge power is reduced on purpose, to safeguard the battery. The last part of a fast charge therefore takes longer per percent.

This calculator keeps full power up to 80 per cent and then reduces it in a straight line to a quarter of full power at 100 per cent. The quarter is an assumption of this calculator, not a measured value; real cars follow their own curves. AC charging is modelled at constant power.

What this calculator does not include

Losses beyond the efficiency you set, and the heating of the battery in cold weather.
The car's own charging limit, or a smaller on-board charger, which can make AC charging slower than the charger's rating.
Session fees and parking charges at public stations, which often differ from the home tariff.

Worked example: 60 kWh from 10 to 80 per cent on a 150 kW DC charger

Energy to the battery: 60 × (80 − 10) ÷ 100 = 42.0 kWh. From the grid at 90 per cent efficiency: 42.0 ÷ 0.9 = 46.7 kWh.

Power into the battery: 150 × 0.9 = 135 kW, with no slowdown below 80 per cent. Time: 42.0 ÷ 135 = 0.311 hours, which is 19 minutes. Cost at 0.25 per kWh: 46.7 × 0.25 = 11.67. Range at 16 kWh per 100 km: 42.0 × 100 ÷ 16 = 263 km.

	Result
Charging time	19 minutes
Energy drawn from the grid	46.7 kWh
Electricity cost	11.67
Range added	263 km

Frequently asked questions

How long does it take to charge an electric car at home?

On a 2.3 kW home socket the model takes about 20 hours for 42 kWh at 90 per cent efficiency. On an 11 kW three-phase wallbox the same charge takes about 4 hours 15 minutes. The calculator gives the figure for the power you choose.

Why does DC charging slow down near 80 per cent?

The charger lowers its power at about 80 per cent state of charge to protect the battery, as the US Department of Energy describes. That is why the last part of a fast charge takes longer per percent.

Is charging efficiency the same as the charger's power?

No. Power is how fast the charger delivers energy; efficiency is the share of the grid energy that reaches the battery. A 150 kW charger at 90 per cent efficiency puts 135 kW into the battery.

How much of the grid energy is lost in charging?

An ADAC test of an 11 kW wallbox recorded about 9.7 per cent losses, and a household socket in the same series lost about 24 per cent. DC losses are an estimate of about 10 per cent in the same source.

How is the range added calculated?

The energy that reaches the battery, divided by the consumption in kWh per 100 km and multiplied by 100, gives the distance. At 16 kWh per 100 km, 42 kWh adds about 263 km.

Should I charge to 100 per cent every time?

The last 20 per cent takes the longest on a DC charger. On a journey it can therefore be quicker to stop near 80 per cent and charge again later; the car's manual gives the battery advice.

Sources

Figures and text last checked on Tuesday, November 10, 2026.

Result