A wallbox is a permanently installed, wall-mounted AC charging station for electric vehicles, technically an electric vehicle supply equipment (EVSE) unit for Mode 3 charging. In EV charging, it is the standard solution for home and workplace parking: it supplies alternating current at a controlled level, typically 3.7 to 22 kW, while the car’s onboard charger converts that current into direct current for the battery.
The wallbox does not charge the battery itself. Its job is to provide a safe, monitored connection and to tell the car how much current it may draw. That makes a wallbox much simpler than a DC fast charger, and much safer and faster than charging from an ordinary household socket.
How a wallbox works
A wallbox works by switching mains power to the vehicle only after a safety handshake and by signaling the maximum permitted current. The handshake follows the control pilot protocol defined in IEC 61851 in Europe and SAE J1772 in North America.
Through the control pilot line, the wallbox sends a 1 kHz square-wave signal whose duty cycle encodes the available current. The car reads that value and sets its onboard charger accordingly. A separate proximity signal tells the car that a plug is inserted and, with tethered or untethered cables, what current the cable can carry. Only when the car signals readiness does the wallbox close its contactor and energize the cable.
Inside the unit, several components make this possible.
| Component | Function |
|---|---|
| Contactor | Switches mains power to the cable on and off |
| Control electronics | Runs the pilot signal and charging logic |
| DC fault current detection | Detects 6 mA DC leakage that could blind a standard RCD |
| Energy meter | Measures delivered energy, sometimes certified for billing |
| Connectivity module | Wi-Fi, Ethernet or LTE for apps and OCPP back ends |
| Cable or socket | Type 2 in Europe, Type 1 or NACS in North America |
Power levels and what limits them
Wallbox power is set by supply phases, current rating and the car’s onboard charger, and the lowest of these values determines the actual charging speed. A 22 kW wallbox charges a car with an 11 kW onboard charger at only 11 kW.
| Configuration | Power | Range added per hour, roughly |
|---|---|---|
| 1 phase, 16 A, 230 V | 3.7 kW | 15 to 25 km |
| 1 phase, 32 A, 230 V | 7.4 kW | 35 to 50 km |
| 3 phases, 16 A, 400 V | 11 kW | 50 to 75 km |
| 3 phases, 32 A, 400 V | 22 kW | 100 to 150 km if the car accepts it |
| North American 240 V, 48 A | 11.5 kW | 50 to 75 km |
The range figures depend on vehicle consumption, which commonly lies between 15 and 25 kWh per 100 km. For most private drivers, 11 kW is more than sufficient, because an overnight session of eight hours delivers far more energy than a typical daily commute requires.
Wallbox compared with other charging options
A wallbox fills the space between slow socket charging and public DC fast charging. Its advantages are safety, convenience and the lowest cost per kilowatt-hour for drivers who can install one.
| Option | Typical power | Best use |
|---|---|---|
| Household socket, Mode 2 | About 2.3 kW | Occasional or emergency charging |
| Portable EV charger | 2.3 to 11 kW | Travel, holiday homes, temporary setups |
| Wallbox, Mode 3 | 3.7 to 22 kW | Daily home and workplace charging |
| Public AC destination charging | 11 to 22 kW | Hotels, shopping, parking garages |
| DC fast charging | 50 to 400 kW | Long trips and quick top-ups |
Household sockets are not designed for continuous high loads over many hours, and older wiring can overheat at the contacts. A wallbox on a dedicated circuit removes that risk and usually costs less over the vehicle’s life than relying on public charging.
Smart features and installation choices
Modern wallboxes add load management, scheduling and energy integration, which often matter more than raw power. The right features depend on the building’s electrical capacity and on electricity tariffs.
- Dynamic load management measures total building consumption and reduces charging current to avoid tripping the main fuse.
- Solar surplus charging follows rooftop photovoltaic output, switching between one and three phases on capable units.
- Time-of-use scheduling shifts charging to cheaper night tariffs.
- OCPP support lets a workplace or property manager connect the wallbox to a billing and management back end.
- Authorization by RFID card or app prevents unauthorized use in shared parking.
Installation must be carried out by a qualified electrician on a dedicated circuit with a suitable miniature circuit breaker and residual current protection, typically a Type A RCD combined with 6 mA DC detection in the wallbox or a Type B RCD. Many grid operators also require notification or approval above certain power levels, commonly 11 kW in parts of Europe.
Common mistakes when choosing a wallbox
The most common mistake is paying for power the car cannot use. Checking the onboard charger rating and the phase count it supports should come first.
| Mistake | Consequence | Better approach |
|---|---|---|
| 22 kW unit for an 11 kW car | Higher cost, approval effort, no gain | Choose 11 kW |
| No load management in a busy home | Tripped main fuse during cooking or heating | Add a meter-based limiter |
| Short tethered cable | Cable cannot reach the charge port | Measure the parking position first |
| No connectivity in shared parking | No billing or access control | Choose OCPP and RFID support |
In plain words
A wallbox is a special power outlet for an electric car, mounted on the garage or carport wall. It checks that the car and cable are connected safely before any electricity flows, then tells the car how much power it may take.
Compared with a normal socket, it is faster, safer and designed for hours of charging every night. Most owners simply plug in when they arrive home and find a full battery in the morning.
A real-world example
A family in a detached house buys an electric SUV with an 11 kW onboard charger and a battery of about 77 kWh. The house has a three-phase connection with a 25 A main fuse, an electric water heater and an induction cooktop.
The electrician installs an 11 kW wallbox with dynamic load management and a sensor at the main distribution board. When the cooktop and water heater run in the evening, the wallbox automatically lowers its current, and it returns to full power once the household load drops.
With a night tariff schedule from 22:00 to 06:00, the car adds more than enough energy for the parents’ combined daily driving of about 70 km. The main fuse has never tripped since installation, and public charging is used only on long holiday trips.