Amazon Basics 68W GaN Charger (PD68U) on a MacBook Air: Measured
Both ports of the Amazon Basics 68W two-port GaN charger, measured on a MacBook Air M5. The USB-C port gives its full 60 W - until you plug something into the USB-A port, and it renegotiates live down to 50 W.
The Amazon Basics 68W two-port GaN wall charger (model PD68U) advertises 60 W on its USB-C port and 18 W on USB-A. Both ports were tested against a MacBook Air M5 with a low battery, per the methodology.
The USB-C port
| Rated | 60 W |
| Negotiated | 60 W (20 V up to 3 A) |
| Live draw | 56.2 W (19.5 V at 2.89 A) |
| Protocol | USB PD 3.0 |
Profile menu: 15 W (5 V/3 A), 27 W (9 V/3 A), 45 W (15 V/3 A), 60 W (20 V/3 A - active). No PPS.
Straightforward: the Mac takes the top rung and gets everything the port advertises.
The USB-A port
| Rated | 18 W |
| Offered | ~8 W (5 V up to 1.5 A) |
| Negotiated | USB BC 1.2 |
| Live draw | 7.2 W (5 V at 1.43 A) |
The 18 W rating is real, but it isn’t meant for laptops. It’s reachable by devices that speak the older fast-charge protocols - Apple’s 2.4 A mode, or Qualcomm Quick Charge. A USB-C Mac speaks neither, so both sides fall back to the strongest standard they share: USB Battery Charging 1.2, capped at 1.5 A. 5 V × 1.5 A = 7.5 W, and the measured 7.2 W is that contract in practice.
The interesting part: a live renegotiation
Plug a load into the USB-A port while the Mac is charging, and the USB-C contract changes while you watch:
| USB-C alone | USB-A also loaded | |
|---|---|---|
| Top profile | 60 W (20 V / 3 A) | 50 W (20 V / 2.5 A) |
| Live draw | 56.2 W | 47.4 W (19.6 V at 2.42 A) |
The voltage rail stays at 20 V; the current allowance drops from 3 A to 2.5 A. The other three profiles don’t move - 45 W still fits under the reduced ceiling, so only the top rung needed re-rating.
The arithmetic explains the model name. 60 W on USB-C plus 18 W on USB-A is 78 W, which is more than this charger has. So once both ports are working it hands USB-A its 18 W and leaves 50 W for USB-C:
50 + 18 = 68 W - exactly its rating. Amazon Basics prints “50-60W” on the USB-C port itself, confirming this is by design rather than a fault.
The lesson generalises to any multi-port charger: the number on the box is a shared power budget, not the sum of what each port can do simultaneously.
A note on the cable
The app reported no e-marker on the cable during this test, meaning a 3 A limit. That isn’t a constraint here - 20 V × 3 A = 60 W is already this charger’s USB-C maximum, so no 5 A cable is required to reach full power. See USB-C 100W vs 240W Cables for when it does matter.
Buying one
The Amazon Basics 68W two-port GaN charger is a competent single-laptop charger. Just don’t expect 60 W and 18 W simultaneously - you get 68 W total, split.
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