EV Talk, kW and kWh: What’s The Difference?
Internal combustion engine (ICE) cars have ruled the road for more than a century. As such, we are already familiar with how they work and the respective unit of measure for power, fuel tank capacity and fuel consumption.
For example, an ICE engine’s power output is measured in horsepower (hp) or ps (Pferdstarke or horse strength in German). In recent times, European countries are starting to favor kW as opposed to the other two, which is also what EV manufacturers use to determine motor output.
kW – electric motor power
EV electric motor power is rated at the SI units kW, which stands for kilowatts. Kilo is a prefix that denotes 1000 units. Watts is a unit of measure for power which equates to the energy consumption of 1 joule(unit for energy) per second.
That means if a motor is rated at 70kW like the BYD Dolphin, it can use 70,000W or 70,000 joules per second to make the car move. The higher the figure, the more powerful the motor, which is like ICE engines where an engine that produces 300hp is more powerful than one that has just 150hp.
The higher the figure, the more powerful a vehicle and the quicker it’s able to accelerate to its top speed. For example, the BYD Dolphin sold in Malaysia comes in two variants: Dynamic Standard which has a 70kW motor while the Premium Extended has a 150kW motor. The former can accelerate from 0-100km/h in 12.3 seconds while the latter can accomplish the same feat in just 7.0 seconds.
Besides the power output of electric motors, kW is also used for charger power rating. This is the basic unit for energy transfer. A charger with a higher kW rating can charge a vehicle faster in the same amount of time as one that has a lower kW rating. However, this also depends on the charging circuitry of the EV in question and whether it’s charging ability can fully utilize the higher power rating.
In comparison, a Samsung Galaxy S23 Ultra supports a charging capacity of 45W. If you choose to use a 65W charger instead of the supported 45W one, it will not mean that your device will charge any faster. That’s because the maximum charging capacity allowed is 45W. However, using a 15W charger will mean that the phone will take significantly longer to charge than if the 45W one was used.
kWh – measure of battery capacity
This brings us to battery capacity. For EVs, this is measured in kWh or kilowatt-hour. This means how much power is stored and can be supplied to the electric motor in an hour. For a 44kWh battery, it can supply a maximum 44kW of power for an hour. It could last longer if it’s required to supply less than 44kW in the same period.
Battery capacity determines range. The higher the kWh rating, the higher the range of the electric vehicle, provided that all other factors remain equal. This is like ICE vehicles, where we use fuel consumption in liters/100km, km/liter or miles per gallon to determine how far it can travel with a liter or gallon of fuel.
A vehicle with a 32mpg fuel consumption rating can travel further on the same amount of fuel compared to one that can only do 15mpg. A battery pack capacity of 60kWh can offer an EV longer range on a single charge compared to one rated at 44kWh. This is only true if all other parameters are kept equal.
We hope this article helped clarify any doubts you have surrounding EV power rating and charging capacity. Stay tuned for more helpful consumer advice.
