When Apple unveiled iOS 9 in June, the company touted the operating system’s new battery saving and power management features, claiming iOS 9 will give your iPhone “even longer battery life.” To achieve this, the operating system itself, native iOS apps, and key technologies have been made more efficient to reduce overall battery usage.

That’s not all that’s changed, though. iOS 9 also has two new power saving features. First off, using ambient light sensors and proximity sensors, an iPhone running iOS 9 intuitively knows when it’s lying facedown on a table and automatically prevents the screen from turning on when you receive a call or notification. Provided you remember to place your iPhone facedown, Apple claims this could give you as much as one hour of extra battery life on a single charge.

The second new power saving feature in iOS 9 — and the one that has the biggest impact —  is a new Low Power Mode. When your iPhone’s battery hits 20 percent you’ll be presented with a popup prompting you to turn on Low Power Mode. If you don’t turn it on at this point, you’ll be promoted again when the battery charge drops to 10 percent.

Low Power Mode disables battery-hungry tasks such as Mail Fetch, Background App Refresh, motion effects, and animated wallpapers, resulting in as many as three hours of extra battery life, claims Apple.

But what if you don’t want to wait for your iPhone’s battery to hit 20 percent before you start using Low Power Mode to extend the battery life? The good news is that you can manually enable Low Power Mode in iOS 9.

How to manually enable Low Power Mode in iOS 9

Enable Low Power Mode in iOS 9 at any battery level by following these steps:

1. Tap on Settings.
2. Tap on Battery (below Touch ID & Passcode).
3. Tap on the Low Power Mode switch to toggle it on (turns green).

With Low Power Mode enabled you’ll note that the battery icon in the top right corner of your iPhone’s screen is now a yellow color.

Theoretically you’ll now get three hours of extra battery life from your iPhone. But this comes at a cost.

The downside of enabling Low Power Mode in iOS 9

In addition to turning off battery-hungry tasks like Mail Fetch, Background App Refresh, and others, Low Power Mode in iOS 9 throttles the iPhone’s processor performance in order to extend battery life.

A benchmark test performed in June using one of the early iOS 9 beta releases showed just how much processor performance is sacrificed when Low Power Mode is enabled:

Using popular benchmarking tool Geekbench 3, MacRumors ran a benchmark test on an iPhone 6 Plus running an iOS 9 beta.

The benchmark test showed that in Low Power mode the iPhone 6 Plus’ multi-core score dropped from 2,891 to 1,751, and single-core performance dropped from 1,606 to 1,019. The publication reported similar results on an iPhone 5s running an iOS 9 beta in Low Power mode, which saw a 40 percent drop in performance.

That’s a significant drop in processor performance that will have a negative impact on any resource intensive apps and tasks like gaming, video playback, etc. But if a few extra hours of battery life is all you’re after, Low Power Mode combined with iOS 9’s other power-saving innovations will do the trick nicely while still allowing you to use your iPhone.

Sources: iGeeksBlog; Apple.com

Image credit: Robin Andeer via Flickr