Apple 10W USB-A Charger (A1357) on a MacBook Air: Measured
Apple's 10W USB-A iPad brick, measured against a MacBook Air M5: 7.1 W delivered, because the Mac won't speak the charger's proprietary protocol and falls back to USB BC 1.2.
The Apple 10W USB power adapter (model A1357) shipped with the early iPads. Tested against a MacBook Air M5 with a low battery, per the methodology.
The numbers
| Rated | 10 W |
| Offered | ~8 W (5 V up to 1.5 A) |
| Negotiated | USB BC 1.2 |
| Live draw | 7.1 W (5 V at 1.43 A) |
Profile menu: one entry - ~8 W (5 V up to 1.5 A). No USB Power Delivery; this predates USB-C entirely.
Why 10 W becomes 7 W
The 10 on the label is real - but it’s Apple’s own number, reached through Apple’s proprietary charging signaling (the 2.1-amp mode that pre-PD iPads used). Modern USB-C Macs don’t implement that legacy signaling, so the two devices meet at the strongest standard they share: USB Battery Charging 1.2 (BC 1.2), whose dedicated-charger mode allows up to 1.5 A at 5 V.
5 V × 1.5 A = 7.5 W. That’s the ceiling, and the measured 7.1 W is that contract minus normal losses.
The notable part isn’t the shortfall - it’s that charging works at all. Delivering 7 W to a laptop is an unusually low-power path for a vendor to bother supporting, and macOS handles it without complaint.
Its sibling, the 12W adapter, lands on exactly the same 7.1 W for the same reason - and the 5W cube is capped by its own hardware instead.
No longer sold
Apple retired this adapter years ago, superseded first by the 12W USB-A model and then by the USB-C line-up entirely. Any you find now are second-hand or old stock.
The modern Apple equivalent for compact charging is the 40W Dynamic Power Adapter (60W Max), which speaks USB-C Power Delivery properly and will charge a MacBook Air several times faster than this brick can.
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