You know, I think the interesting part is how good will it be initially.
Some aspects I think matter:
-A 2800 mAh battery isn’t necessarily too small. My iPhone Xʀ on iOS 12 (2,942 mAh) gives me 16 hours of light SOT. About 12 hours of outdoors, settings-efficient LTE use.
For reference to current iPhone users, my 16 Plus gives me about 27 hours of
light Wi-Fi SOT and 17-20 hours of cellular, outdoors, settings-efficient use.
Can a 17 Air match the Xʀ with its processor efficiency vs the higher efficiency of iOS 12? Can it give 16 hours of light SOT? I don’t think so:
A 6th-gen iPad (8,827 mAh) gave me 14 hours of SOT on iOS 12 with an A10 vs the same 14 hours of my 9.7-inch iPad Pro (7,306 mAh)… on iOS 9. It gets about 10.5 hours on iOS 12.
How much better does an A19 Processor needs to be vs an A12 to overcome the difference in iOS 26’s inefficiency and heavier requirements? TBD.
-The VAST majority of users are ridiculously inefficient. Heavy, battery-draining apps with high brightness and all settings enabled. That kills battery life. My 2,942 mAh iPhone Xʀ lasts three full days, and to give an example, this was an actual full cycle: 12h 51 min of SOT with 27% remaining over three full days (say, unplugged with 100% Jan 1 at 09:00 and recharged Jan 3 at 22:00).
Users can probably kill an iPhone Xʀ on iOS 12 in under 10 hours with current usage patterns, most likely even less.
If the combo of the A19 + iOS 26’s inefficiency is significantly worse than the A12 + iOS 12 with similar battery size, this coupled with users’ heavy, inefficient usage, we’re in for many complaints. I’d expect something a little better than the 13 Mini on iOS 15 (2,406 mAh). That one, according to what I’ve seen, gave about 6-7 hours of SOT with moderate usage. Heavy users could probably kill it in 4 hours. So maybe iPhone XS on iOS 12-like? 8-9 hours of moderate? Shouldn’t be too poor for light to moderate users.
It has no longevity vs current models, though. Forget about it withstanding many iOS updates with good battery life.