USB C to HDMI With Charging: How Power Delivery Passthrough Works
Quick answer / TL;DR: Short answer: look for the phrase 'power delivery passthrough' with an explicit wattage (65W, 100W) in the spec – not a USB-A port labeled 'charging'. Passthrough routes your laptop charger's power through the device to the laptop over the USB C link. A separate USB-A 'charging port' that powers phones or dongles is a different, much weaker feature and will not charge your laptop.
A 'USB C to HDMI with charging' product is doing three jobs through one port: video out, power through, and (usually) USB data. The feature everyone wants is the middle one – power delivery passthrough, which lets the same USB C port that feeds your monitor also feed your laptop's battery. But 'with charging' on a product box hides two very different designs, and only one of them keeps a modern laptop alive all day.
This article explains what PD passthrough is, the wattage math that decides whether it is enough, and how to read a spec sheet to avoid a dongle that 'charges' at 5W while your laptop drinks 65W.
Passthrough vs. the Lookalike 'Charging Port'
| Feature | What it actually does | Charges laptop? | Where it appears |
|---|---|---|---|
| PD passthrough (USB C) | Routes charger power through the device to the laptop | Yes, up to rated wattage | Hubs, some docks |
| USB-A 'charging' port | Draws 5V from bus power to feed small devices | No – it is the consumer, not the source | Budget dongles |
| USB C data port | Plain USB data | No | Budget dongles |
This distinction explains most 'it does not charge' complaints in reviews: the product had a USB-A port, the buyer expected laptop charging, and the physics said otherwise.
The Wattage Math
- Match passthrough rating to the laptop's rated charging input (45W / 65W / 100W / 140W)
- Buy headroom: a 100W passthrough on a 65W laptop is safe and useful later
- Remember the display and USB ports draw a few watts from the same budget – the laptop receives passthrough minus device consumption
- Above ~100W requires EPR-capable hubs and laptops; most hubs stop at 100W
Which Form Factor Suits Which Setup
| Setup | Best form | Why |
|---|---|---|
| Laptop + one display + full charge | 3-4 port hub with PD passthrough | Frees the charger into the hub, adds USB |
| Laptop in a dock daily | Thunderbolt/USB C dock | Full PD, multiple outputs, stable thermals |
| Occasional use, port available | PD-enabled 2-in-1 dongle | Simplest, still keeps charging alive |
| Laptop has a spare port | Plain HDMI dongle + separate charger | Cheapest; no passthrough needed |
Verified PD test curves and per-SKU wattage behavior are not provided in the knowledge base. For fleet orders, request the supplier's PD negotiation report (advertised power vs. delivered power) for your laptop models.
Real-World Applications
Fleet IT refreshes
Standardizing hubs by laptop wattage class (45W / 65W / 100W) turns 'my laptop is dying at my desk' tickets into non-events.
Multi-room hotel stays
A single hub cable carries the laptop's charger, the TV display and a phone – one wall outlet, one tangle.
Trade show booths
Demo laptops run all day on shared PD through display stands; passthrough wattage is specified per booth to match the demo hardware.
Related reading: Running video + USB + charging together? Read our one-port guide — blogs/news/usb-c-to-hdmi-and-usb
Related reading: Browse PD-enabled hubs and dongles — collections/usb-c-hubs
Frequently Asked Questions
Does PD passthrough reduce my laptop's charging speed?
Only if the device's own consumption plus the laptop's demand exceeds the hub's rating. Sized correctly, the laptop charges at its full native rate.
Can I charge the hub's USB-A phone port while the laptop charges?
Yes, but both draw from the same PD budget. The laptop is prioritized; small-device charging continues as long as total draw is under the hub's rating.
Why does my dongle show 'charging slowly' on the laptop?
The dongle is likely a data-only or 5W USB-A design with no real PD passthrough, so the laptop is negotiating a low-power profile.
Is 100W passthrough safe for a 65W laptop?
Yes. PD is a negotiated protocol – the laptop requests what it needs, and the hub supplies up to its maximum.
Looking for a verified, spec-matched USB C to HDMI solution for your project? Contact our engineering and B2B sales team for datasheets, compatibility test reports, and volume pricing. Request a quote or sample.