Apple 12W USB-A Charger (A1401) on a MacBook Air: Measured
Apple's 12W USB-A adapter - the iPad 4's charger - measured against a MacBook Air M5: 7.1 W delivered, identical to the 10W model, while a USB-C iPhone still pulls the full 12 W.
The Apple 12W USB power adapter (model A1401) first shipped with the 4th-generation iPad in late 2012, when the bigger battery needed more than the old 10W brick could provide. Tested against a MacBook Air M5 with a low battery, per the methodology.
The numbers
| Rated | 12 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.
Why 12 W becomes 7 W
The full 12 watts is only reachable through Apple’s proprietary 2.4-amp signaling, which pre-dates USB-C. To be USB-C compliant, Apple’s laptops dropped support for that legacy mode - so charger and Mac 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 7.1 W is that contract in practice.
To a modern Mac, this adapter and the 10W model are indistinguishable: same fallback, same ceiling, same 7.1 W.
The iPhone twist
Here’s the detail that makes this brick interesting: a modern USB-C iPhone still pulls the full 12 W from this adapter. The iPhone kept support for Apple’s legacy signaling; the Mac gave it up for USB-C compliance. Same charger, same cable-era protocol - one Apple device speaks it, the other no longer does.
Buying one
This adapter still floats around in large numbers - it was bundled with iPads for years - and is still sold on Amazon. As a slow overnight iPhone charger it remains perfectly good; as a Mac charger, expect 7 W, not 12.
Apple itself no longer sells it. For a current Apple adapter, the 40W Dynamic Power Adapter (60W Max) is the modern compact option.
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