Slow, fast, rapid and ultra-rapid charging: what the kW numbers mean
How charging speed is measured, and roughly how long a charge takes at each speed.
Charging speed is measured in kilowatts (kW). The higher the number, the faster energy flows into the battery, up to the limit your car can accept.
The four speeds
- Slow, up to about 7kW: home charging, overnight, on-street posts.
- Fast, 7kW to 22kW: supermarkets, car parks and workplaces. A few hours for a useful charge.
- Rapid, 50kW to 149kW: service stations and charging hubs. Usually 30 to 60 minutes.
- Ultra-rapid, 150kW and up: motorway hubs. Often 20 to 40 minutes for cars that can take it.
Working out charging time
A rough guide is energy needed (kWh) ÷ charging power (kW) = hours. Adding 40kWh on a 7kW charger takes about 5.7 hours. On a 50kW rapid charger it takes under an hour.
In practice, rapid charging slows down as the battery fills, especially above about 80%, and your car's maximum charging rate caps the speed. That's why rapid charging stops are usually planned from around 10–20% up to 80%.
Why didn't I get the full speed?
- Your car's maximum DC or AC charging rate is lower than the charger's.
- The battery is cold, or already nearly full.
- Power is being shared between two cars at the same unit.
To see what a charge costs at each speed, try the EV charging cost calculator.