How your phone’s low power mode actually works

Give your phone’s battery a better chance.

Smartphone battery life is a precious resource: If you don’t manage it carefully, you might find yourself unable to make calls, take photos, or check social media by the end of the night. A dead phone is pretty much useless until you can find a charging point.

To extend your phone’s battery capacity, Android and iOS both have a special battery-saving mode that helps your handset hang on just a little longer.

This mode will automatically kick in when your battery level drops below a certain point, but you can customize where that trigger is, and even turn the mode on manually if you’re happy with the compromises that it makes.

How low power mode works

So, what’s the catch? Low power mode reduces the amount of juice your device needs, so it’s not quite running on all cylinders. It works in more or less the same way whether you’re on an iPhone or an Android phone.

Screen brightness is a big battery drain, and low power mode will dim your display accordingly. It will also reduce the time your phone waits before going to sleep, which, again, helps ease the pressure on the battery.

Any kind of constant checks or refreshes that your phone does drains its battery. Going into low power mode means your phone will run these tasks less often—for incoming emails or updated news stories, for example. Your phone will also disable background uploading and downloading in most apps, so your photos and videos won’t sync with the cloud while battery-saving measures are in effect. You won’t be able to use a “Hey Siri” or a “Hey Google” voice command, either.

Another major battery suck is 5G connectivity. If you turn on low power mode with a 5G phone, it will revert back to 4G.

Even though the basics are the same, there are a few differences between how Android and iOS apply low power mode. On Android devices, for example, dark mode turns on right away—this doesn’t happen on iPhones. On iOS, the software disables some of the “visual effects” it uses, but Apple doesn’t specify which effects are switched off.

Low Power Mode on iOS

a screenshot of the Low Power Mode toggle switch in iOS
Apple’s Low Power Mode can save your phone, and turning it on is as easy as touching this switch. David Nield

Low Power Mode for iOS doesn’t turn itself on automatically, but your iPhone will prompt you to enable it via a pop-up dialog box once its battery level hits 20 percent. The mode does automatically turn itself off though—once you’ve got your handset back up to 80 percent charged.

You can turn Low Power Mode on or off any time you like, by opening Settings, then tapping Battery and Low Power Mode. You can also add a Low Power Mode toggle switch to the iOS Control Center: from Settings, open Control Center and choose Customize Controls.

With the mode enabled, the battery icon in the status bar will be yellow. Swipe down from the top right-hand corner of the screen to see the current battery level, or go back to the Battery section within Settings. That screen will also show you the apps that are the worst offenders in terms of battery drain.

Not all of the changes Low Power Mode makes are locked in place. You can, for example, ramp the brightness back up. Other changes to the settings, like the length of time it takes for the screen to automatically lock and the extent to which apps can be active in the background, can’t be reconfigured.

Battery Saver on Android

a screenshot of the battery level indicator in Android's Battery Saver low power mode
Android will judge how long your battery is likely to last for. David Nield

The stock version of Android that runs on Google Pixel phones features Battery Saver. Your device prompt you to enable it when the battery level drops to 15 percent, and then again at 5 percent if you still haven’t turned it on. By default, the mode automatically disables itself once the charge reaches 90 percent.

To turn Battery Saver on manually, choose Battery, then Battery Saver from Android Settings. Tap Turn on now to enable the mode, or choose Set a schedule—this will let you specify what power level will trigger Battery Saver. You can also get Android to automatically enable its low power mode if it thinks your phone won’t make it to the next charge, based on previous usage habits. For fast access, you can find an on-off toggle switch in Quick Settings (swipe down from the top of the screen with two fingers).

With Battery Saver on, dark mode turns on and the battery icon in the status bar gets a red outline. Swipe down from the top of the screen to see how much time Android estimates the battery will last for; if you go back to the Battery screen in Settings, you can see this estimate and turn on a percentage reading for the battery in the status bar.

Android being Android, you’ll see different battery-saving options on different phones, though they all work in a similar way. On Samsung phones, for example, tap Device Care, Battery, and then Power mode to choose how aggressively the phone manages the battery. As you switch between modes, you’ll be able to configure some of the settings used, such as display brightness.

Correction April 30, 2021: The story previously reported that it was possible to change the auto-lock time while in Low Power Mode for iOS. That is not possible.

David Nield

David Nieldis a tech journalist from the UK who has been writing about gadgets and apps since way before the iPhone and Twitter were invented. When he's not busy doing that, he usually takes breaks from all things tech with long walks in the countryside.