Apple 35W Dual USB-C Power Adapter on a MacBook Air: Measured
Apple's 35W dual-port USB-C adapter measured on a MacBook Air M5 twice: 32.6 W with one port in use, and roughly half that once the second port is occupied.
Apple’s 35W dual-port USB-C power adapter (product ID 0x701A), tested against a MacBook Air M5 with a low battery, per the methodology. Measured twice - once with a single port in use, and once with both - because the two readouts are not the same charger.
One port in use
| Rated | 35 W |
| Negotiated | 35 W (20 V up to 1.75 A) |
| Live draw | 32.6 W (19.5 V at 1.67 A) |
| Protocol | USB PD 3.0 |
Profile menu: 15 W (5 V/3 A), 27 W (9 V/3 A), 35 W (15 V/2.33 A), 35 W (20 V/1.75 A - active).
Full marks. The adapter delivers exactly what it claims, and offers its full 35 W on two separate rails - 15 V and 20 V - so a device can pick whichever suits its converter.
Both ports in use
| Negotiated | 17.4 W (20 V up to 0.87 A) |
| Live draw | 16 W (19.7 V at 0.81 A) |
Profile menu: 15 W (5 V/3 A), 17.5 W (9 V/1.94 A), 17.4 W (15 V/1.16 A), 17.4 W (20 V/0.87 A - active).
Every rung above 5 V has halved. The 35 W profiles are gone entirely - they are no longer advertised, so there is nothing for the Mac to negotiate. The top contract falls from 1.75 A to 0.87 A on the same 20 V rail.
35 W is the adapter’s total, not the port’s
This is a shared power budget, and seeing it in both states makes the design unambiguous: the 35 W on the label belongs to the adapter as a whole. With one device attached, that device gets all of it. Attach a second, and the adapter re-advertises a smaller menu to each.
The important detail is how it does this: it doesn’t fail, throttle, or misbehave. It republishes its profile list. Whatever a port is advertising at the moment you look is exactly what you can have, which is why reading the profile menu beats reading the label.
The Amazon Basics 68W demonstrates the same principle even more dramatically - its USB-C contract drops from 60 W to 50 W live, while you watch, the instant its USB-A port is loaded.
What this means in practice
- Charging one MacBook Air: you get the full 35 W, and it’s a genuinely good compact charger.
- Charging a laptop and a phone together: the laptop gets roughly 17 W, which is trickle territory.
Neither is a fault. But “35 W” describes the first case only, and the second is the one people actually buy a dual-port charger for.
Buying one
The Apple 35W USB-C Compact Power Adapter is a capable single-device charger and a convenient two-device one - as long as you expect about half the rating per port when both are working.
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