I work on the manufacturing side of USB-C hubs, and there is one complaint that comes back so consistently that it is worth explaining properly: the laptop is plugged in, through a 100 watt hub, and the battery is still going down.
The hub is not lying to you. It is keeping some of the power for itself, and it is doing that because it has to.
Here is the arithmetic. A hub advertising 100 watt passthrough takes 100 watts in from your charger. It then reserves somewhere between 12 and 20 watts to run its own electronics, to convert the DisplayPort signal into HDMI, and to power the peripherals you plug into it. What it passes through to the laptop is the remainder, and that is why the honest products print a second number, usually 85 watts or 87 watts, lower down on the page.
If your laptop is happy on 60 or 65 watts, which most thin ones are, this arrangement works fine and you will never notice.
If your laptop wants 96 watts, which some 16 inch models do under load, then 85 is less than 96, and the battery discharges slowly while you work. The charger is delivering its full rated output. The hub is spending part of it. And the laptop reports that it is connected to a charger, which is the confusing part, because it is, just not to a sufficient one.
There are three fixes and they are worth doing in this order.
The direct one is to skip the passthrough for power. Many laptops with two ports will charge perfectly happily with the charger in one port and the hub in the other, and this bypasses the hub's power budget entirely. It uses a second port but it removes the whole problem, and it is what I would do at a desk.
The second is to size the charger up rather than the hub. A 140 or 180 watt charger feeding a hub that reserves 15 watts leaves 125 or 165 available, and at that point even a power-hungry laptop charges normally. The hub did not need to be better; the input did.
The third is to reduce what the hub is powering. Every bus-powered device you attach comes out of the same budget as your laptop. A portable hard drive can draw four or five watts on its own, and two of them plus a conversion chip plus a receiver is a real load. If a drive clicks or drops out when a second one is attached, that is the budget being exceeded, and the fix is a hub with its own external power supply rather than a bigger charger.
The other half of this category is video, and the mistake there is assuming that all 4K is the same 4K.
A hub gets its display output by carrying a DisplayPort signal over the USB-C connection, and that signal shares the available high-speed lanes with the data. Driving 4K at 60 hertz with full colour needs substantially more bandwidth than 4K at 30 hertz. Hubs that support the former generally say 4K60 explicitly; hubs that only manage the latter say 4K, or say 8K in a way that is technically true at 30 hertz and practically misleading.
The consequence people notice is that their external monitor works, and their mouse and keyboard attached to the same hub behave sluggishly, or their external drive drops to slow speeds. That is the lane budget being spent on the display. It is not a fault. It is a shared resource.
There is one physical thing to know, which is that the chip doing DisplayPort to HDMI conversion gets genuinely warm. A hub that is warm in normal use is fine; a hub that is hot enough to be uncomfortable is usually one with a conversion chip in a plastic shell with no heat path, and those are the ones that develop intermittent display dropouts after an hour. An aluminium case is worth something here, and it is not purely cosmetic.
Practical version, in short.
Read the passthrough number, not the input number. If the listing only ever says 100 watts and never says what reaches the laptop, assume the lower figure.
If you can, charge the laptop directly and use the hub for everything else.
If your monitor matters, buy a hub that states 4K at 60 hertz by name, and accept that the USB ports on it are sharing bandwidth with the display.
If you are running bus-powered drives, use a hub with its own power supply, or expect them to drop.
On the manufacturing side, the reservation is not a markup trick. A hub has to power itself, and its own consumption is not optional. The reason the honest spec sheets look worse than the dishonest ones is that we print both numbers, and the sellers who print only the big one are not better engineers.
ODMKit develops USB-C hubs and wall chargers for brand owners, on OEM and ODM programmes from Shenzhen. Full product range and manufacturing capability.
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