Re: IOS slow or increased battery usage?
Here's what Apple and some Trade Press have to say:
Performance and battery impact
Apple’s hardware and software are designed together to deliver great performance and great battery life. As new features and improvements are added, they can change the way we use our devices, as you explore and utilize these new capabilities. Here are some important things to keep in mind:
Immediately after completing an update, particularly a major release, you might notice a temporary impact on battery life and thermal performance. This is normal, as your device needs time to complete the setup process in the background, including indexing data and files for search, downloading new assets, and updating apps.
New features are exciting and help you get even more out of your Apple product, though some may require additional resources from the device. Depending on individual usage, some users may notice a small impact on performance and/or battery life. Apple continually works to optimize these features in software updates to ensure great battery life and a smooth user experience.
from:
About Apple software updates - Apple Support
The main takeaway? After installing iOS 26, or any other major software update, there will be an initial period of additional background processing that puts a strain on your device. This should be a non-issue after the first couple days.
from:
https://9to5mac.com/2025/09/15/apple-explains-why-ios-26-could-affect-your-iphones-battery-life/