It’s easy to confuse a kW and a kWh, so much so we have seen it in charger company brochures!
Here’s the difference:
- A kW (kilowatt) is a unit of power, measuring the rate at which energy is being used at any given moment.
- A kWh (kilowatt-hour) is a unit of energy, measuring the amount of energy consumed over time.
In other words, a kW is a rate and a kWh is an amount.
For example, a 100-watt light bulb uses 0.1 kW of power when it is turned on. After being turned on for 1 hour, that same light bulb will have used 0.1 kWh of energy.
What this means for charging an EV
When it comes to charging an electric vehicle (EV), a kW is the rate at which the battery is being charged and a kWh is the amount of energy being put into the battery.
To determine how long it will take to charge an EV battery, you will need to know both the kW of the charger and the kWh of the battery.
The higher the kW of the charger, the faster the battery will charge, while the higher the kWh of the battery, the more energy it will need to be fully charged.
For example, a 7.4kW home charger will give you between 28 and 30 miles of range per hour, while a 50kW charger adds around 100 miles in 35 minutes.
For most people charging at home, 7kW is enough.
Summing up
kW is a measure of the rate at which electricity is used over a given period of time, while kWh is a measure of the total amount of energy consumed over a given period of time. For example, a 1 kW device uses 1 kW of power per hour, but will consume 1 kWh of energy in one hour.
