Charging electric cars in 2025: calculate charging time and realistically estimate range

The charging time essentially depends on two values: On the usable battery capacity in kilowatt hours (kWh) and on the applied charging power in kilowatts (kW). Charging times can be roughly calculated using the following formula.

Formula

Charging time in hours = battery capacity in kWh / charging power in kW

Sample calculation

A vehicle with 77 kWh charges at a fast charging station with 125 kW for around 0.62 hours. That corresponds to around 37 minutes. In reality, the value fluctuates because vehicles do not charge continuously at maximum power.

• Household socket (2.3 kW): Only suitable for occasional charging. An empty battery takes many hours to charge, depending on its size.
• Wallbox (11 kW): The standard in companies and at home. A battery with 60 kWh takes roughly five to six hours from almost empty to full.
• Public AC charging (22 kW): Halves the time compared to 11 kW. The vehicle must support a 22 kW onboard charger, otherwise the car will be limited.
• DC fast charging (50 to over 300 kW): Delivers from 50 to over 300 kW, depending on the station and vehicle. In practice, the window from around 10 to 80 percent battery level is relevant because this is when the highest charging power is available.

Important: The shortest practical time rarely results from simple division. The charging power follows a curve. It rises after the start, remains stable in the optimum range and drops significantly from around 70 to 80 percent. When on the road, it is therefore usually worth charging up to around 80 percent and continuing to drive.

Battery temperature and weather conditions: Batteries charge most efficiently at moderate temperatures. In extreme cold and heat, the battery management system reduces the current flow. Many vehicles offer preconditioning. The thermal management system brings the battery into a favorable temperature window before fast charging.

Start charge level and target charge level: The higher the battery level, the lower the charging power. This makes the last few percent significantly slower.

Vehicle-side limits: The onboard charger limits AC charging. In DC charging, cell chemistry and battery management limit the maximum output.

Voltage architecture of the vehicle: An increasingly important factor is the voltage architecture. Models with 800-volt technology (as used by Hyundai, Kia, Porsche and Audi, for example) can often maintain even higher and more stable charging performance over a longer period of time. In practice, this enables charging times from 10 to 80 percent in under 20 minutes at corresponding high-power charging (HPC) stations.

Charging losses: Conversion losses occur during charging. For rough planning purposes, a surcharge of around 10 percent on the amount of energy is a sensible reserve.

Station and utilization: The power may be reduced at shared charging points. The actual charging power depends on the station, the cable and the grid utilization.

Battery ageing: Batteries lose some capacity over years and cycles. This changes the range and charging window. Frequent DC charging is possible, but continuous maximum charging power over long periods of time increases ageing.

The distinction between WLTP range and practical range is crucial. The WLTP measurement provides cross-manufacturer comparative values. In everyday life, the driving profile and conditions influence the actual distance.

Practical formula for e-car range

Range in km = (Usable battery capacity in kWh / average consumption in kWh/100km) * 100

Example

(60 kWh / 17 kWh/100km) * 100 gives around 353 kilometers.

To put this into perspective: Many current passenger cars require between 14 and 22 kWh per 100 km in mixed operation. Compact vans and vans require more like 20 to 30 kWh per 100 km.

Weather: Cold increases the energy requirement due to heating power and the battery status. Heat requires cooling.

Tempo: Air resistance increases disproportionately with increasing speed. A range of 100 to 110 km/h is often efficient.

Vehicle design and tires: Aerodynamics, tire width and rolling resistance have a direct effect on fuel consumption.

Payload and roof attachments: Weight and attachments such as roof boxes reduce the range.

Consumers in the interior: Heating, air conditioning, seat and rear window heating increase demand.

Driving style and recuperation: Anticipatory driving and frequent coasting make use of energy recovery and noticeably improve the range.

• Small car: approx. 250 to 400 km. Suitable for urban and rural areas.
• Compact class: approx. 350 to 550 km. Universal use including highway.
• Middle and upper class: approx. 500 to 700+ km. Long distances can be planned with short fast charging breaks. Models in these classes, especially those with efficient 800-volt architecture, currently occupy the top positions in range lists and thus directly serve the search for electric cars with the longest range.
• Light commercial vehicles: approx. 200 to 350 km. Often ideal in the city with consistent intermediate charging.

Planning in loading windows: Charge up to around 80 percent on the road. Shorter stops are more efficient.

Use on-site charging: Overnight at the 11 kW wallbox provides predictable availability at calculable costs.

Load management and billing: Intelligent charging solutions distribute power, prioritize vehicles and simplify billing.

Simplify processes with Plug & Charge: The Plug & Charge function (in accordance with ISO 15118) is becoming increasingly important for company fleets. It enables automatic authentication and billing directly via the charging cable. All the driver has to do is plug in the vehicle – there is no need for a charging card or app. This simplifies the process, reduces administrative work and makes it easier to allocate charging costs to the exact vehicle.

Training for employees: A short guide to recuperation, speed and preconditioning increases the range in everyday life.