Zoeftig Under Seat Boost Airport Charger on a MacBook Air: Measured
The USB-C port on a Zoeftig airport seat's Under Seat Boost module, measured on a MacBook Air M5: a real 25.5 W Power Delivery contract, and the first charger in this series where the Mac skipped the 20 V rung for more watts at 15 V.
I’d rather arrive at the airport with a full battery. After three tries at a wall outlet, I plugged my MacBook Air into the USB-C port on the seat instead. Two surprises: it’s a real Power Delivery charger, and it showed exactly how a Mac chooses between charging profiles.
The seat is made by Zoeftig, whose airport seating is installed in airports worldwide. The charger is its Boost power module in the under-seat configuration, which Zoeftig sells as “Under Seat Boost”.
The numbers
| Source | Zoeftig Boost power module, under-seat (airport seating) |
| Negotiated | 25.5 W (15 V up to 1.7 A) |
| Protocol | USB PD 3.0 |
| Reports as | nothing, shows as “PD Charger” |
| Cable read | No e-marker read, 3 A |
Profile menu:
| Profile | Rail |
|---|---|
| 15 W | 5 V up to 3 A |
| 20 W | 9 V up to 2.22 A |
| 25.5 W | 15 V up to 1.7 A (active) |
| 24 W | 20 V up to 1.2 A |
The Mac stepped down to get more watts
Look at the last two rows. The 20 V rung offers 24 W. The 15 V rung below it offers 25.5 W. The Mac took 15 V.
That’s the first time in this series a Mac has chosen anything other than the highest voltage. Every charger tested so far offered its most power on its top rail, or offered the same power on several rails, and the Mac took the highest voltage each time. This seat port is the first one where the top rail offered less, which settles the order. The Mac goes for watts first, then volts. More in how a Mac picks a charging profile .
A budget of about 25 watts
The odd currents, 1.7 A and 1.2 A, are what a charger offers when it has a fixed power budget to split across its rails. 15 V at 1.7 A comes to 25.5 W, and 20 V at 1.2 A comes to 24 W. Seat modules like this may share one power supply across several seats, which could explain the tight budget, but the readout can’t show that.
Every rung is under 3 amps, so the cable doesn’t matter here. Any USB-C cable gets the full 25.5 W.
Is it worth plugging into?
As a charger, yes. 25.5 W is real Power Delivery, and it charges a MacBook Air, just slowly. Think hours, not minutes. It’s a top-up at the gate, not a fast charge.
The readout also shows what didn’t happen. The Mac saw a charger and nothing else: no data device appeared alongside it, only “PD Charger”. That doesn’t prove a public port is safe, but it does show this one behaved like a plain charger.
It never names a brand over Power Delivery. The Zoeftig name comes from the seat, not from the charger, which is normal for built-in chargers like this.