With every iOS update comes concerns about the battery. We're at iOS 8 beta right now so it would be too early to talk about iOS 8 battery issues/concerns. However, with all the new features, old devices are obviously going to buckle down. And it's a good time to start assessing it.
In iOS 8, Apple has introduced a “Battery usage per app” feature that lets you figure out how much battery every app you use consumes. This is useful, but it's not an ultimately controlling feature. Nevertheless, there's always performance tweaks that the engineers introduce to make sure there is good battery performance.
Also Read: How to Improve iOS 8 Battery Life
iOS 8 is supported on iPhone 5s, 5, 4s, iPod 5th gen and iPad 3 and up. It drops support for iPhone 4, older iPods and iPads. That's the norm with almost every iOS upgrade.
Device compatibility not only talks about processing and memory but also about battery support. iOS 8 is not vastly different from iOS 7 regarding interface, but there are definitely huge changes in the way iOS 8 works. Features like Continuity, Handoff, etc. are not only cool features, but they require quite a bit of processing (which in turn involves battery).
iOS 8 Battery Life
On the iPad, iOS 8 should show no large change from iOS 7 regarding battery performance. That's the expected result. On iPhones, the changes can be visible. For instance, iPhone 4s can show a drop in the battery backup after iOS 8 is finally released.
From Beta to GM to Final Release
iOS 8's Grand Master is expected to hit the shelves in fall (about the same time as an iPhone 6). There will be plenty of revisions before that, and one of the things the developers would be looking for is battery performance. There will be a lot of optimization given the scope of the new features. But if there's one thing that is bound to happen, it's a varied landscape of battery performances across users, across devices.
In the beta, our tests are not as exhaustive so the battery performance, for the moment, is pretty decent. In fact, there's no considerable change from the time of iOS 7. But this is accompanied by the fact that we haven't put our iPads through extensive tests.
Whatever optimization is done at the code level, it is up to users to drive better battery performance out of their devices – and that's based on app usage, network usage, brightness and the load.