ZDNET’s key takeaways
iPhones are updating to iOS 27.
A new OS can affect battery life.
These steps can boost your power.
Upgrading your iPhone’s operating system to a new version can considerably affect its battery life, especially in the first couple of days. As a result, you may notice your iPhone draining its battery faster than usual or running some processes slowly.
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A major iOS upgrade can mean your iPhone runs more background tasks than usual, tasks that use significant CPU power and can even make your phone feel warmer. These background tasks include rebuilding search indexes, analyzing data, and completing other system setup processes.
Before making major settings changes, restart your iPhone and use built-in battery-saver features, like Adaptive Power and Low Power Mode, even temporarily. If these tactics don’t work, here are other things you can do to ensure your iPhone runs more efficiently after upgrading to iOS 27.
1. Change your display settings
An iPhone’s display consumes a lot of energy. Thankfully, a few tweaks can help your phone run more efficiently. One tweak is using Auto Brightness, which helps keep your iPhone display from being unnecessarily bright.
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To turn on Auto Brightness, follow these steps:
Open your iPhone Settings.
Navigate to Accessibility.
Select Display and Text Size.
Turn on Auto Brightness.
2. Turn on Adaptive Power
Adaptive Power mode helps conserve battery by automatically lowering the display’s brightness, limiting background activity, and adjusting extra consumption when your battery usage is unusually high.
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Adaptive Power is already on by default on the iPhone 17 lineup and newer, as well as the iPhone Air. To turn the setting on in older models, follow these steps:
Open your iPhone Settings.
Go to Battery.
Select Power Mode.
Toggle on Adaptive Power.
3. Update all apps at once
Third-party applications also get their own updates with a fresh operating system, as they need to fit the new firmware rolled out with iOS 27. These background app updates can consume battery power.
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Luckily, you can run all available updates at once to avoid staggered updates that drain your battery during the day.
Here’s how you can update all your apps with available updates at once:
Go to the App Store.
Tap your profile icon.
Go to App Updates.
Select Update All.
Try this approach when your iPhone is plugged in and connected to Wi-Fi, so you don’t use your battery.
4. Make some network changes
Changing your network settings can help you save precious battery life, especially after an iOS update. These changes include ensuring your iPhone connects to Wi-Fi rather than cellular when Wi-Fi is available, and potentially turning off 5G and staying with LTE.
Since cellular networks consume more energy than Wi-Fi, it’s more efficient to switch to Wi-Fi when a secure network is available. Your iPhone battery drains quicker in a poor cellular service zone. The device constantly attempts to reconnect to the network when the signal is poor, which consumes considerably more energy.
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If no secure Wi-Fi network is available, see if your 5G signal is weak and switch to LTE. This change may slow your online activity, but a weak 5G signal drains an iPhone’s battery more quickly than LTE.
To switch from 5G to LTE on iOS 27, follow these steps:
Access your Settings.
Select Cellular.
Go to Cellular Data Options.
Navigate to Voice and Data.
Tap on LTE.
Using 5G Auto helps optimize battery life by automatically switching from LTE when 5G isn’t required for performance. Choosing 5G On maintains 5G connectivity, even if it affects your battery life.
5. Adjust background app behavior
Background activity is one of the biggest culprits for a device’s short battery life, especially right after a major software update like iOS 27.
In addition to rebuilding indexes and updating applications for compatibility, your iPhone also continues to refresh apps in the background.
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You can temporarily turn off background app refresh for non-essential applications by going to Settings > General > Background App Refresh.
Location services can also run in the background and consume your battery. See which applications have location services enabled at all times by going to Settings > Privacy & Security > Location Services. Check unnecessary apps with location services set to Always and switch them to While Using, even if temporarily.
6. Always keep tabs on battery health
It’s important to check your iPhone’s battery health, whether or not you’re experiencing power issues.
You can check your iPhone’s battery health by going to Settings, then selecting Battery. Scroll down to find Battery Health, which shows the iPhone’s maximum capacity and cycle count and provides a battery health qualifier.
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A Normal battery health qualifier means your battery is running as it should, while a Service qualifier means that you should consider a battery replacement.
iOS 27 has a Daily Usage view that shows that day’s battery consumption compared to the previous week. This view helps you identify apps and system activities that use unusually high energy.
7. Be a little patient
Upgrading to iOS 27 entails re-indexing files and photos for Spotlight search and the newer AI-powered search features. With Siri AI, your iPhone needs to reanalyze data to update the models that power Siri’s new generative AI features.
Shorter battery life on your iPhone is normal for the first couple of days after installing a new iOS. Unless your iPhone is unusually hot while not in use, shorter battery life doesn’t mean that there’s cause for concern.
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If you’re curious whether your iPhone has finished running background processes and indexing after updating to iOS 27, go to Settings, and then Battery. A note with “Ongoing iOS Update” will appear on this page if the system is still running background processes.
Maria Diaz is a staff writer with a passion for home automation, smart home devices, and tablets. With a background in graphic design, photography, and filmmaking, she has a bachelor’s in Mass Communication and experience in journalism and film.
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