In much of Europe, the difference between a 7 kW and an 11 kW wallbox is not the hardware price but the number of phases. Three-phase supply makes higher AC charging power possible, but only if the car can use it and the building has it. Understanding phases avoids disappointment for drivers and costly mistakes in site design.
- On a European 230/400 V supply, single-phase charging gives 3.7 kW at 16 A or 7.4 kW at 32 A; three-phase gives 11 kW at 16 A or 22 kW at 32 A.
- The car's on-board charger decides how many phases it uses; some cars charge on one or two phases only.
- Many countries limit single-phase load imbalance in buildings, which caps single-phase charging current.
- On multi-charger sites, rotating phase connections spreads load evenly and increases usable capacity.
Phases in brief
A three-phase supply delivers power over three conductors whose voltages are offset in time. In Europe, each phase has about 230 V to neutral and about 400 V between phases. Homes in some countries have only one phase; commercial buildings and many newer homes have three. North America uses a different system: residential Level 2 charging typically runs on 240 V split-phase, which is single-phase from the car's perspective.
Charging power by phases and current
| Supply | Current per phase | Approximate power |
|---|---|---|
| Single-phase, 230 V | 16 A | 3.7 kW |
| Single-phase, 230 V | 32 A | 7.4 kW |
| Three-phase, 400 V | 16 A | 11 kW |
| Three-phase, 400 V | 32 A | 22 kW |
| Split-phase, 240 V (North America) | 32–48 A | 7.7–11.5 kW |
The car decides, too
An AC charger only offers power; the car's on-board charger decides how much to take and on how many phases. Common cases:
- Three-phase 11 kW on-board charger: the most common setup in Europe today.
- Three-phase 22 kW on-board charger: available on some models, often as an option.
- Single-phase on-board charger: some cars, especially older or smaller models, charge on one phase only, at 3.7 or 7.4 kW even on a 22 kW point.
- Two-phase charging: a few models use two phases, giving around 7.4 kW at 16 A.
This is why a 22 kW public AC point often delivers 11 kW, and why some cars charge surprisingly slowly on three-phase chargers. Our guide on charging times shows the effect.
Phase imbalance limits
When a single-phase load draws high current, the three phases of a building become unevenly loaded. Network rules in several countries limit this imbalance. In Germany, for example, the permitted unbalanced load is typically 4.6 kVA, which limits single-phase charging to about 20 A. Check the rules of your network operator before relying on single-phase 7.4 kW charging on a three-phase site.
Phase rotation on multi-charger sites
If every single-phase car on a site draws from phase L1, that phase overloads while L2 and L3 sit idle. Installers solve this with phase rotation: each charger is wired with its phases shifted (L1-L2-L3, L2-L3-L1, L3-L1-L2), so single-phase cars are spread across all three. Combined with load management that knows which phase each charger uses, rotation lets more cars charge on the same connection. Our guide to smart charging and load management explains the software side.
1/3-phase switching and solar charging
Some chargers can switch between single-phase and three-phase operation during a session. This is useful for solar surplus charging: at low surplus, single-phase charging at 6 A (about 1.4 kW) is possible, whereas three-phase charging needs at least about 4.1 kW (6 A per phase). Switching phases mid-session must be supported by both charger and car, and some cars react poorly to frequent switching.
Phases in OCPP smart charging
OCPP charging profiles can include the number of phases to use, and limits can be expressed in amps per phase or in watts. When a management system sets a limit in amps on a three-phase charger, the resulting power is roughly three times higher than the same limit on a single-phase charger. Configuring phase information correctly for each charger is therefore essential for accurate load management.
Planning tips
- Check the supply: confirm whether the site has three-phase power and how much capacity per phase is available.
- Match the car fleet: for fleets, check the on-board chargers of the vehicles you will charge.
- Install three-phase where possible: it future-proofs the site even if today's cars use one phase.
- Rotate phases on sites with several chargers.
- Configure load management per phase, not just as a total power figure.
Our comparison of 11 kW and 22 kW wallboxes helps choose the right charger power once the supply is known.
Frequently asked questions
Can I charge at 11 kW on a single-phase supply?
No. 11 kW requires three phases at 16 A. On a single phase, the practical maximum is around 7.4 kW at 32 A, and often less due to imbalance rules.
Why does my car charge at 7 kW on a 22 kW charger?
Your car probably has a single-phase or limited on-board charger. The charger offers 22 kW, but the car decides how much it takes.
Is three-phase charging better for the battery?
AC charging at 11 or 22 kW is gentle for the battery either way. The difference is mainly charging time and grid load balance.
What is phase rotation?
Connecting chargers on the same site with shifted phase order, so single-phase cars are spread evenly across all three phases instead of overloading one.
Set per-phase limits, balance load across chargers and see live current per connector from one OCPP dashboard. Explore Üreticy OCPP software or contact us.