By Jason Snell

September 18, 2015 11:16 AM PT

iOS 9 in review: Low Power Mode and lowering battery anxiety

Note: This story has not been updated for several years.

When you think of operating-system updates, of course you think about whizzy new features. In iOS 9, that means dramatic improvements to iPad productivity, new proactive search features, improvements to Maps, Safari content blockers, and a whole lot more.

But lurking behind the scenes in iOS 9 is an update that may have more impact on your life as a iPhone user than any one of these in-your-face features—improvements that allow you to extend the battery life of your device.

Overall, if you do nothing, Apple claims that “across the entire operating system” battery usage has been optimized in iOS 9. I haven’t tested these claims methodically, and beta versions of operating systems are infamous for being all over the place when it comes to battery life. There are times when it feels like iOS 9 has improved the battery life of my iPhone 6, and other times when I appear to be draining the battery at an alarming rate. But then, that’s how I felt when I was running iOS 8, too.

If iOS 9 does really extend battery life in normal use, Apple deserves a medal. Improving battery life by optimizing software is a huge improvement for users, even if it’s all imperceptible to them. There’s probably not an iPhone user alive who would not say they wish their battery just had a little more juice in it. Apple can’t retroactively upgrade our iPhone batteries, but it can tweak its software to use that juice more judiciously.

But while I can’t offer a chart comparing iOS 8 battery life to iOS 9 right now, I can endorse another power innovation of iOS: Low Power Mode. This past weekend I was at a conference where I was out and about (and away from any convenient way to charge my iPhone) for most of the days and nights. These are the kind of days you dread, when you need to use your iPhone to call an Uber or to navigate your way back to the hotel or just to call a friend to see where they ended up—and you know that by the time you need to do those things, that phone will be dead as a dinosaur.

On day one of the conference, I just used my iPhone normally, until at some point in the early evening when it popped up a warning that only 20 percent of its battery life remained. This warning (and another one at 10 percent) have been in iOS for a while; what’s new in iOS 9 is that the warning prompts you to enable Low Power Mode.

When an iPhone enters Low Power Mode¹, iOS 9 turns off all but the most essential activities on your phone in order to hoard power. Surprisingly, this doesn’t make your iPhone feel particularly poky. The most I noticed is that I had to wait for some apps to load data from the Internet when I launched them, presumably because they weren’t allowed to refresh that data in the background.

According to Apple, Low Power Mode kills background network connections and automatic downloads, reduces CPU and GPU performance, reduces screen brightness, auto-locks your iPhone more quickly, turns off Mail fetching, and disables all motion effects and animated wallpapers. Apps can also detect Low Power Mode and pitch in. (In Low Power Mode, iOS 9 also turns on the display of your battery percentage next to the battery icon, and the contents of the battery of the icon turn from black into bright colors indicating just how worried you should be.)

So when my iPhone got to 20 percent, I tapped the button to enter Low Power Mode and hoped that it might allow me to go the rest of the night without needing a charge². And indeed it did! In fact, it seemed like my battery indicator stalled. I went for several more hours with no appreciable loss in battery. The balloon just stopped deflating.

That night, I recharged my iPhone’s battery—once it gets to about 80 percent full, it turns off Low Power Mode automatically, which is a nice touch—and at lunch time the next day I decided to preemptively switch on Low Power Mode. Honestly, I never felt like I was missing much by doing so, and all my anxiety about getting through the day without running out of battery just faded away. I don’t know if I recommend that you live a Low Power Mode life, but turning it on early on a day when I knew my battery would be pushed to the limit made me feel more comfortable. And yes, the phone lasted all day with juice to spare.

The focus on batteries extends to the Settings app, which now features a top-level Battery entry. (Previously, battery settings were in a submenu inside the Usage entry.) This menu continues to display which apps are using power over the last 24 hours or 7 days, and now offers a clock icon that lets you see how much time they’ve spent on the screen and how much time they’ve used running in the background.

The Battery menu also provides you with useful tips about settings that you can change to improve your battery life. For instance, when I turned off the Auto-Lock setting—meaning my iPhone would just continue to stay on until I pressed the sleep button—the Battery menu prominently displayed a “Battery Life Suggestions” section with an entry suggesting that I enable Auto-Lock. Tapping on that suggestion took me directly to the Auto-Lock section of the Settings app. (Another suggestion I received was to turn on the Auto-Brightness feature.) This is a feature that apparently appeared intermittently in iOS 8—though I never, ever saw it—but, of course, buried down in General: Usage: Battery. Now it’s front and center in the Battery menu and appears consistently.

It seems like it will be a long time before iPhones offer substantially longer battery life, given Apple’s propensity to solve for x when designing their devices. But at least iOS 9 suggests that Apple’s interested in extending the life of the battery that’s already there—and giving users the opportunity to trade off some features in order to keep their iPhones going long into the night.

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