An 11kW onboard charger is the AC-to-DC converter built into the car, and 11kW is the fastest AC power it can accept. On a three-phase supply the car can draw the full 11kW. On a single-phase supply it charges more slowly, typically about 3.7 to 7.4kW, because the converter can only use part of its capacity on one phase. The rating belongs to the car, not to the wallbox: no home charger can push AC power in faster than the onboard charger accepts.
Key Takeaways
- The onboard charger is inside the car and converts AC to DC; its rating caps AC charging speed.
- 11kW needs a three-phase supply. On single-phase, expect roughly 3.7 to 7.4kW.
- Home chargers are not all 7kW: three-phase homes can run 11kW and 22kW units.
- Match the charger to the car and the supply, not to the biggest number available.
The Onboard Charger Is in the Car, Not the Wallbox
Batteries store DC power, but homes supply AC. With AC charging, the conversion happens inside the car, in the onboard charger. The wallbox or portable charger is essentially a controlled, protected AC supply: it tells the car how much current it may take, and the car does the rest. That is why two cars on the same wallbox can charge at different speeds.
DC fast charging is the exception. A DC charger converts AC to DC in the charging station itself and feeds DC straight to the battery, bypassing the onboard charger. So the 11kW figure says nothing about rapid charging speed. The U.S. DOT guide to charger types and speeds lists AC Level 2 charging at 7 to 19kW, which is the range onboard chargers work in.
What 11kW Means in Practice
The slower of the two ratings always wins: the supply and the car. This table shows the common combinations.
| Supply and charger | Car’s onboard charger | AC power the car takes |
|---|---|---|
| Three-phase wallbox, 11kW or more | 11kW | Up to 11kW |
| Three-phase wallbox, 22kW | 11kW | 11kW, the car sets the limit |
| Single-phase wallbox, 7.4kW | 11kW | About 3.7 to 7.4kW, depending on the car’s design |
| Three-phase wallbox | 7.4kW single-phase | About 7.4kW, using one phase |
For time, work in kilowatt-hours. At 11kW the car adds roughly 11kWh of energy per hour, before losses. A 60kWh battery charged from empty would take around five to six hours. Our guide to how long charging takes at 7kW, 11kW and 22kW works through more battery sizes.
Are All Home Chargers 7kW?
No. 7kW, more precisely about 7.4kW, is simply the common size for a single-phase home supply, which is what most UK and European houses have. Homes with a three-phase supply can run 11kW or 22kW chargers. The difference between single-phase and three-phase charging decides which sizes are even possible at a property, and our 11kW vs 22kW wallbox comparison covers which one makes sense to install.
Chargers That Can Feed an 11kW Car
If your car has an 11kW onboard charger and your home has three phases, a three-phase charger lets it use its full speed. The ACS1605PE 11kW three-phase portable charger runs at 16A three-phase on a CEE 5-pin plug, with a Type 2 connector and a 7.6m cable. For a fixed installation, the EV-ACT3204PE 22kW wallbox covers an 11kW car today and a 22kW car later; the car still only takes 11kW. A qualified electrician should confirm the supply type before you buy either.
Frequently Asked Questions
Do I need a three-phase home supply to charge at 11kW?
Yes. The 11kW figure is reached across three phases. On single-phase, the same car typically charges at about 3.7 to 7.4kW, depending on how its onboard charger is built.
Can I install a 22kW wallbox for an 11kW car?
Yes, if the property has a three-phase supply. The car will charge at 11kW, and the larger wallbox leaves room for a future car with a 22kW onboard charger.
Where do I find my car’s onboard charger rating?
Check the owner’s manual or the maker’s specification page for “AC charging” or “onboard charger”. It is listed separately from the DC rapid charging figure, which is usually much higher.
Related Reading
- Single-Phase vs Three-Phase EV Charging: 7kW, 11kW and 22kW Explained
- How Long Does It Take to Charge an EV at 7kW, 11kW and 22kW?
- 11kW vs 22kW Wallbox: Which Should You Install?
