Short answer: When two or more charging stalls share a single power cabinet, splitting the available power between connected vehicles.
Explanation
Many DC fast chargers are built so that two stalls share one power unit. If only one car is plugged in, it gets the full power. When a second car connects, the available power is split between them. This means your charging speed can drop significantly when another car parks at the paired stall next to you.
You can sometimes spot shared stalls by their labeling (A and B on the same unit), but not always. The charger screen might show a lower maximum power than expected when the adjacent stall is occupied. If you were charging at 150 kW and someone plugs in next to you, your speed might drop to 75 kW.
This is increasingly common at 150 kW charger installations. Ultra-rapid 350 kW stations are less likely to share power, but some still do. If speed matters, try to pick a stall where the paired stall is empty. Some charging apps show whether a charger uses power sharing, but the most reliable way to know is to watch your kW reading after someone plugs in next to you.
Where you'll see this
- On the charger screen
- In charging network apps
Common confusion
Drivers often blame the charger for slow speeds without realizing that power is being shared with the car plugged in at the adjacent stall. Moving to an isolated stall can instantly double your speed.
Example
A charger pair rated at 150 kW total will deliver up to 150 kW if one car is connected, but only about 75 kW each when two cars are connected simultaneously.
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