Many users notice that when charging their laptop through a 100W USB-C docking station or hub, the actual power delivered is typically around 85W to 87W, not the full 100W. This is not a defect or malfunction—it’s normal behavior due to safety and system design considerations.
Power Reservation Explained
Although a docking station may support up to 100W of Power Delivery (PD), a portion of this power is intentionally reserved for the hub’s internal operation and connected peripherals, such as USB devices, Ethernet ports, card readers, or HDMI outputs. This reserved power ensures stable performance and prevents overheating or sudden shutdowns during high-power tasks.
What Happens Under the Hood?
To maintain a safe and efficient power supply, manufacturers typically design USB-C hubs and docking stations to deliver a maximum safe power output of about 85W to 87W to the connected laptop. This pre-allocation ensures stable operation under all conditions.
What This Means for Users
Most modern laptops are fully compatible with this setup and will operate and charge normally when receiving 85W–87W of power. In fact, for many laptops, 85W is more than sufficient for charging even while under load.
Conclusion
Seeing 85W or 87W instead of 100W is not a limitation—it’s a safety feature. Understanding this power distribution helps users make informed choices and avoid unnecessary concern when reviewing the power output of their docking station.
