EV Charging Speed Demystified: What is the difference between kW, kWh, and Voltage?

If you are planning to buy an Electric Vehicle (EV) or have just bought one, you have probably stared at the spec sheet and felt confused. Terms like kW, kWh, and Voltage are everywhere.

Unlike a petrol car, where you just need to know "Liters," an EV requires a little clearer understanding of electricity to know how far you can drive and how fast you can charge.

Don't worry! Here is a simple guide to understanding these terms using a very easy analogy: A Water Pipe.

1. Voltage (V) = The Pressure

Imagine you are holding a water hose. Voltage is the water pressure.

• If the pressure is low, the water trickles out.
• If the pressure is high, the water shoots out forcefully.

In an EV, Voltage determines how much "push" the electricity has.

• Why it matters: Higher voltage systems (like 800V architectures found in newer premium EVs) allow electricity to flow more efficiently and with less heat. This usually means the car can accept a charge much faster.

2. Kilowatt (kW) = The Charging Speed

This is the most important number when you are waiting at a charging station. kW stands for Power.

Using our water analogy, kW is the speed at which the water is filling up your bucket. It is the result of the Voltage (Pressure) and the Current (Amperage/Pipe width) working together.

• Low kW (e.g., 3 kW or 7 kW): Like a kitchen tap. It will fill the bucket, but it takes a long time. This is your typical home AC charger.
• High kW (e.g., 50 kW, 150 kW, or 350 kW): Like a fire hose. It fills the bucket incredibly fast. This is DC Fast Charging.

Simple Rule: The higher the kW number on the charger, the less time you spend waiting.

3. Kilowatt-hour (kWh) = The Tank Size

If kW is the speed, kWh is the capacity.

Think of kWh as the size of the bucket (or the size of the fuel tank in a petrol car).

• Small kWh (e.g., 24 kWh): A small bucket. It fills up fast, but it empties fast (less range).
• Large kWh (e.g., 80 kWh): A massive drum. It takes longer to fill up, but allows you to drive for a very long time (more range).

The Math is easy:
If you have a 60 kWh battery (bucket) and you use a 60 kW charger (speed), it will take exactly 1 hour to fill up from 0 to 100%.

Summary: The Cheat Sheet

Conclusion

Next time you look at an EV, remember:

• Look at kWh to know how far it can drive (Range).
• Look at kW to know how fast it can charge (Speed).
• Look at Voltage to understand the system's efficiency.

Understanding these three terms makes owning an EV much simpler!