Quick Answer / Summary: Laptops charge over USB C via USB Power Delivery: ultrabooks need 45-65 W, mainstream 65-90 W, workstations 100-140 W. The cable must be e-marker rated for the wattage (5 A above 60 W), and any adapter or hub in the path must pass the full wattage. Charging works at lower wattage – just slower – and fails entirely when CC negotiation is broken by cheap wiring.
One charger for phone, tablet and laptop is the USB-C promise – and it works, with conditions written in watts and wire gauge. This page gives the wattage ladder, the e-marker rule, what adapters and hubs do to charging, and a diagnosis path for ‘plugged in, not charging’ over USB C.
The Wattage Ladder
Phone-class: 18-30 W. Ultrabooks: 45-65 W. 14-inch mainstream: 65-90 W. 16-inch and workstations: 100-140 W (and beyond with vendor extensions). The charger negotiates down gracefully: a 65 W brick charges a 45 W ultrabook at full rate and a 100 W workstation at reduced rate – slower, but functional.
Reading Charger Labels
Output lines like ‘5V/3A, 9V/3A, 15V/3A, 20V/3.25A’ are PD profiles; the top line’s product is the wattage ceiling. A charger listing only 5V/2A (10 W) cannot charge most laptops meaningfully.
Cables: The E-Marker Rule
Above 60 W (20 V/3 A), USB-C requires an e-marker chip in the cable advertising 5 A capacity. Non-marked cables negotiate 60 W maximum no matter the charger. For 100 W-plus laptops, buy cables labeled ‘100 W’ or ‘240 W’ with e-markers; for 45-60 W ultrabooks, quality 60 W cables suffice.
Adapters, Hubs and Pass-Through
Every device in the charging path must pass the wattage: a hub with 60 W pass-through caps a 90 W laptop at 60 W. Simple A-to-C adapters are irrelevant here – A sources never offer PD wattage. The clean chain is: PD wall charger, e-marked C-to-C cable, laptop port marked for charging.
Laptop Charging Requirements by Class
| Laptop Class | Typical PD Need | Cable Requirement | Notes |
|---|---|---|---|
| Ultrabook 13-14″ | 45-65 W | 60 W cable (3 A) | Charges from phone-grade PD bricks, slower |
| Mainstream 14-15″ | 65-90 W | 100 W e-marker cable | 65 W works, reduced rate |
| Workstation 16″+ | 100-140 W | 100/240 W e-marker | Vendor bricks often required for full rate |
| Gaming | 100-240 W | Vendor-specific | USB C usually for travel, not gaming loads |
Real-World Application Scenarios
A consultant travels with one 65 W PD brick and an e-marked cable for ultrabook and phone; a studio standardises 100 W GaN chargers at every desk with labeled 100 W cables; a fleet manager audits charging chains after ‘slow charge’ tickets and replaces two cable models missing e-markers.
Recommended Internal Resources
Editorial Note: Chargers and cables live in USB C Cables and Chargers and USB C Power Adapters; cable standards in USB Type C Cables.
Frequently Asked Questions (FAQ)
Q: Can I charge a laptop with a phone charger?
A: Yes at reduced rate if the charger is PD and offers 18-30 W. An ultrabook will charge slowly overnight; a workstation may gain little.
Q: Why is my laptop charging slowly with a 100 W charger?
A: Check the cable: non-e-marked cables cap at 60 W, and hubs with 60 W pass-through cap the chain. The charger label alone does not decide the rate.
Q: Is it safe to charge a laptop with any USB C cable?
A: Safe if the cable is rated for the wattage. Underspecified cables warm under 5 A loads. Use e-marked cables for above-60 W charging.
Q: Does charging through a hub work?
A: Yes when the hub has PD pass-through rated at or above the laptop’s need. Lower-rated pass-through silently throttles charging speed.