When charging an electric vehicle, you will frequently come across the abbreviations kW and kWh. Although they look similar, they describe two different values. Understanding the difference helps you estimate charging times, compare vehicles and interpret the information shown at a charging station.
The abbreviation kW stands for kilowatt and is a unit of power. When charging an EV, it indicates how quickly electrical energy can be transferred to the vehicle. A 150 kW fast charger can generally provide more energy per unit of time than a 50 kW charging point. Under ideal conditions, it could theoretically transfer three times as much energy over the same period.
However, the actual charging power also depends on the vehicle. If an EV can accept a maximum of 100 kW, it will charge at no more than 100 kW, even when connected to a 300 kW charger. The charging point’s higher output cannot override the vehicle’s technical limit.
When charging with alternating current, or AC, the vehicle’s onboard charger also determines the maximum power it can accept. Many EVs charge at up to 11 kW using a wallbox or public AC charging point. With direct current, or DC fast charging, electricity flows directly into the battery, allowing for considerably higher charging power.
Kilowatt-hours, abbreviated as kWh, measure an amount of energy. For electric vehicles, the unit is used to describe factors such as battery capacity. An 80 kWh battery can store more energy than a 50 kWh battery.
An electric vehicle’s energy consumption is also measured in kWh. For example, if a vehicle uses 18 kWh per 100 kilometres, it consumes approximately that amount of energy to cover the distance under the given conditions.
The distance you can travel on one charge does not depend on battery capacity alone. Speed, outside temperature, driving style, heating, air conditioning and the type of route all affect the vehicle’s real-world range.
kW and kWh answer two different questions. The value in kW shows the power at which the electric vehicle is currently charging. The figure in kWh tells you how much energy has been transferred to the battery in total.
For example, if a vehicle charges at an average of 100 kW for 15 minutes, it theoretically receives around 25 kWh of energy. To calculate this, the 15 minutes must first be converted into hours. As 15 minutes is one quarter of an hour, the charging power of 100 kW is multiplied by 0.25 hours: 100 kW × 0.25 h = 25 kWh. In this example, the kW figure describes the charging rate, while the kWh figure shows how much energy has been added over that period.
You can also see this distinction on the charging station display. The current charging power is usually shown in kW, whereas the amount of energy delivered and the resulting cost are generally displayed in kWh.
You can estimate the charging time by dividing the amount of energy required by the average charging power. The average power is more useful for this calculation than the maximum peak figure.
Suppose a 60 kWh battery needs to be charged from 20% to 80%. This means that 60% of its total capacity must be added. The calculation is: 60 kWh × 0.60 = 36 kWh. The required 36 kWh is then divided by an average charging power of 120 kW: 36 kWh ÷ 120 kW = 0.3 hours. Multiplying 0.3 hours by 60 gives an estimated charging time of 18 minutes. In practice, charging losses and variations in power may make the process slightly longer.
A larger battery does not therefore automatically result in longer charging stops. The key factors are how much energy is required and how consistently the vehicle can maintain a high charging power.
Charging speed rarely remains constant throughout a session. At a low battery level, the battery can usually accept a relatively high amount of power. As the state of charge, or SoC, increases, the battery management system gradually reduces the charging power. This is why many electric vehicles charge particularly quickly between approximately 20% and 80%.
Battery temperature also affects charging performance. If the battery is too cold or too warm, the vehicle reduces the charging power. Some models can precondition the battery before a fast-charging stop, bringing it closer to the ideal operating temperature.
Once the conditions within the vehicle are suitable, the available power at the charging point also becomes important. JOLT brings battery-buffered fast-charging stations to urban areas, making high charging power available in convenient city locations. This allows you to use short stops to add the range you need for your next journey.
You are a journalist and want to reach our team? You want to sign up for press distribution list?
You need our press kit and brand assets? here is everything your might need.
