What we’re expecting
Multiple sources report Apple prioritized battery capacity over adding Touch ID this cycle. Combined with S12 3nm efficiency and a likely LTPO display improvement, battery life should beat the Series 11's 24 hours. No hour count has been reported, but the trade-off shows Apple made this a primary target.
Apple's reportedly trading new Series 12 hardware for battery life, letting the S12 chip do more per charge instead of adding sensors. Touch ID was on the table and got cut, not because Apple doesn't want it but because a fingerprint reader would eat battery or crowd out health features. Battery is the top smartwatch gripe, so it's the right thing to spend the room on.
How does Apple Watch Series 12's battery life compare?
Standalone runtime per charge, longer is better.
Tethered and USB-C-powered devices excluded (no standalone rating).