Apple 87W USB-C Power Adapter on a MacBook Air: Measured
Apple's 87W USB-C adapter measured on a MacBook Air: an 86 W contract at 4.3 A, using the older USB PD 2.0 specification.

Apple’s older 87W USB-C power adapter, tested against a MacBook Air with a low battery, per the methodology.

The numbers
| Rated | 87 W |
| Negotiated | 86 W (20 V up to 4.3 A) |
| Live draw | 68.4 W (19.6 V at 3.49 A) |
| Protocol | USB PD 2.0 |
Profile menu: 12 W (5 V up to 2.4 A), 27 W (9 V up to 3 A), 86 W (20 V up to 4.3 A).
A missing rail and an old spec
This adapter predates the modern USB Power Delivery 3.0 standard. It uses the older USB PD 2.0 specification, which explains some of its quirks.
Most notably, it skips the 15 V rail entirely. Modern USB PD 3.0 chargers generally step through 5 V, 9 V, 15 V, and 20 V profiles. The absence of the 15 V rail can cause issues with devices that require it (like older Nintendo Switches or specific power banks), but the Mac happily jumps straight to the 20 V rail.
Additionally, the 5 V rail tops out at 2.4 A (12 W) rather than the standard 3 A (15 W) found on almost every modern charger.

A 5A cable requirement
The top 86 W profile negotiates at 4.3 A. Because this exceeds the 3 A limit of a standard USB-C cable, a 5A cable is required to reach the full power of this adapter.