Your home has three phases and the car accepts 11 kW alternating-current (AC) charging, yet the display shows barely more than 4 kW. Looking at total household consumption, it seems there should be room for more. Charging may also be constrained by how the home's load is distributed across the three phases.
It is worth understanding this before shopping for a higher-powered charger. The same charger may deliver more if additional current becomes available on the heavily loaded phase.
Three phases mean three separate limits
Imagine a connection that provides 25 A on each phase. You need to check the spare current on each one separately. Spare capacity on one phase cannot simply be transferred to another that is already almost fully occupied by the kitchen.
Many cars capable of three-phase AC charging draw the same current on every phase. In that situation, the tightest phase sets the charging current across all three. Total power alone therefore does not tell you what the car can draw.
Look for the relevant figure in the car's AC charging specification. The much larger kW figures quoted for public direct-current (DC) rapid chargers describe a different situation.
Where did the apparently spare power go?
The example below assumes a nominal phase voltage of 230 V and a 25 A limit per phase. The household loads do not yet include the car.
| Phase | Household load | Spare current |
|---|---|---|
| L1 | 19 A | 6 A |
| L2 | 7 A | 18 A |
| L3 | 5 A | 20 A |
Together, the figures appear to show 44 A of spare capacity. But a car that draws the same current on every phase can receive only 6 A on each. Its power is therefore about 3 × 230 V × 6 A = 4140 W, or 4.14 kW.
No energy has disappeared: some of the spare capacity on phases two and three simply remains unused. If the household load on phase one later falls to 9 A, that phase will also have 16 A free. The car in our example could then reach roughly 11 kW, provided the other conditions are met.
This is, of course, a simplified calculation. Cable sizes, protection, configured reserves and actual voltages all form part of an installation design.
You notice the difference when it is time to leave
Suppose 12 kWh needs to pass through the charger. At a constant 4.14 kW, this takes about 2 hours 54 minutes; at 16 A per phase, or a nominal 11.04 kW, it takes about 1 hour 5 minutes.
Either may work if the car stays at home all night. If you need to leave again in an hour and a half, however, it matters whether the household load restricting charging falls away in the meantime.
That leads to two possible actions. If there is enough time before departure, you can wait out a short peak. If a large load regularly occurs on the same phase, ask for it to be examined specifically during the electrical survey.
What can the different forms of phase management do?
Load balancing that follows household consumption controls how much current can be made available for charging. Where several cars charge on a shared system, the distribution of load across the phases can also be planned.
Zaptec Pro offers dynamic phase and load balancing for shared charging installations. This can help coordinate cars with different charging capabilities within the available capacity. Read more in the manufacturer's Zaptec Pro overview.
Switching between single- and three-phase charging is a separate matter: the same car uses either one phase or three. It can be helpful at lower power, for example with fluctuating solar surplus.
What does Go 2 phase switching mean in this example?
In single-phase operation, Go 2 uses the phase connected to the charger's L1 terminal. If there is little spare capacity on that phase, changing from three phases to one does not move the constraint to either of the other phases.
The switching described by the manufacturer requires a three-phase connection, an installation configured as three-phase, an online connection and suitable Zaptec control. It is unavailable in Standalone mode or with native OCPP authentication. Switching back to three phases must be enabled separately and also depends on the car. The Go 2 phase-switching guide explains the settings. OCPP is a communications standard used between a charger and an external management system.
The right question is therefore which operating method helps in your home. The wiring, car and controls together determine which feature you can use.
Bring phase-by-phase figures to the next discussion
First find the car's exact AC charging specification. Then note the main-fuse rating on each phase and the larger household loads. Finally, record when you see low charging power and how long remains before you need to leave.
A qualified professional can use this information to investigate the load distribution. It will clarify not just which charger to choose, but also where and when genuinely usable capacity is available.
Phase data makes it easier to choose the right charger
On our contact page, tell us your car model, the main-fuse rating for each phase and the charging power you have observed. We can then help you choose a suitable Zaptec solution.
