The Apple Watch Series 12 and Ultra 4 charge faster than last year's models. There's a catch. You only get the faster speed with Apple's new charging puck, and your old ones won't do it.
MacRumors confirmed that the new Apple Watch Magnetic Fast Charger, model A3277, delivers up to 10W. The previous puck tops out at 5W. The new one comes in the box with both watches. Apple also started selling it on its own last week, for $29 in the US, with a one meter cable.
Apple says 15 minutes on the new charger adds 12 hours of battery to the Series 12 and 18 hours to the Ultra 4. Last year's Series 11 and Ultra 3 got 8 hours and 12 hours from the same 15 minutes.
Here's what trips people up. Speed needs both halves. The Series 12 and Ultra 4 have hardware changes that let them take the extra power, so a new puck on an old watch does nothing. An old puck on a new watch charges at the old rate. According to Apple's figures, the Series 11 and Ultra 3 get exactly the same 8 and 12 hours whichever charger you use.
MacRumors reports you need a USB-C Power Delivery adapter rated at 10W or higher for the fastest speed. A small, old adapter will hold you back.
So what should you do?
If you're buying a Series 12 or Ultra 4, use the puck in the box and plug it into a decent USB-C adapter. That's it.
If you keep spare chargers around, on a nightstand, in a travel bag, at your desk, those are probably the old 5W kind. They'll still charge the new watch. They just won't charge it fast. Whether $29 a spot is worth it depends on how often you top up in a hurry.
If you're staying on a Series 11 or Ultra 3, don't buy the new puck for speed. You won't get any.
Faster charging is one of the quieter upgrades this year, and it matters more than it sounds. A watch that can gain half a day of battery during a shower is a watch you can wear to bed. It just helps to know which cable you're holding.