Why won't my plug-in hybrid or older electric vehicle charge at full power – despite an 11 kW or 22 kW wallbox?
Many people are surprised: the new 11 or 22 kW wallbox is on the wall, but the car still only charges at 2–4 kW. It is easy to assume that the wallbox is faulty or incorrectly installed. Usually, though, this is completely normal – and has technical and regulatory reasons.
Key points at a glance
- The onboard charger in the car determines the charging power, not the wallbox.
- Many plug-in hybrids and older electric cars only charge on a single phase.
- In Austria, single-phase charging is limited to 16 A, or around 3.7 kW.
Many vehicles only charge on a single phase
Modern wallboxes such as the Compleo SOLO smart provide 11 kW (3 × 16 A). This power is available – but the car often does not draw it. That is because the onboard charger in the vehicle determines how much is actually charged.
Many vehicles charge:
- on a single phase only,
- at a maximum of 16 A,
- or have small, low-cost chargers that do not allow higher power.
This mainly affects:
- almost all plug-in hybrids (VW, BMW, Mercedes, Volvo, Ford, Toyota …)
- many older electric cars (e.g. Nissan Leaf, older Hyundai Ioniq, older generations of the Renault Zoe)
Austria: the 16 A phase imbalance limit
In Austria, the Technical and Organisational Rules (TOR) apply. Under these rules, a maximum of 16 A may flow on a single phase – equivalent to around 3.7 kW. The reason: an even load across the phases keeps the distribution grid stable.
Important: A vehicle that only charges on a single phase cannot charge faster than around 3.7 kW AC in Austria – regardless of whether you have an 11 or 22 kW wallbox.
Why 11 kW is not always 11 kW
The power of the wallbox is not the same as the charging power of the car:
| Device | Phases | Current | Max. power |
|---|---|---|---|
| 11 kW wallbox | 3 | 16 A | 11 kW |
| 22 kW wallbox | 3 | 32 A | 22 kW |
| Single-phase car | 1 | 16 A | 3.7 kW |
| Two-phase car | 2 | 16 A | 7.4 kW |
| Three-phase car | 3 | 16 A | 11 kW |
If your car only charges on a single phase, it stays at around 3.7 kW – even on the best wallbox.
Why do plug-in hybrids charge particularly slowly?
Plug-in hybrids have relatively small batteries and are designed for short commutes in electric mode. It is therefore sufficient for them to charge slowly overnight or during working hours. Many manufacturers therefore fit simple single-phase onboard chargers with 10–16 A and around 2.0 to 3.7 kW. That is enough to fully charge the battery in a few hours.
Why don't older electric cars charge faster?
Three-phase AC charging at 11 kW used not to be standard equipment. Many older models have 3.3 or 6.6 kW chargers, often also single-phase. Examples:
- Nissan Leaf (older models): single-phase, 3.3–6.6 kW
- Hyundai Ioniq (older generation): single-phase, 6.6 kW
- Renault Zoe (older generation): depends on grid quality and charger generation
Why does my car sometimes show less than 3.7 kW?
Even 3.7 kW is not always possible on a constant basis. Possible reasons:
- cold battery – charging limitation
- hot battery – thermal protection
- limitation due to the connected load or load management
- PV surplus mode of the wallbox
- charging limit set in the car
This is not a fault but a protective mechanism.
Future-proof with the Compleo SOLO smart
Even if your current vehicle only charges on a single phase, a modern wallbox such as the Compleo SOLO smart is worthwhile:
- integrated Type A RCD – no external RCD required
- integrated surge protection
- MID meter for company car billing
- backend connection via OCPP
- ready for future electric cars with 11 kW three-phase charging
- PV surplus charging possible (with an energy manager)
You can read more about single-phase charging in 11 kW or 22 kW wallbox connected on a single phase.
Conclusion
If your plug-in hybrid or older electric car does not charge at the full wallbox power, this is due to:
- the single-phase charging capability of the vehicle,
- the Austrian phase imbalance limit of 16 A,
- the technical limits of older onboard chargers.
The wallbox is almost never the problem. For most plug-in hybrids, the charging power is perfectly sufficient – and if you later switch to a modern electric car, you can use the full 11 kW straight away.
