You'll be able to save a ton of battery life on your iPhone soon.

One of the new features in iOS 9, the upcoming operating system for iPhones and iPads, is a low-power mode that will extend your device's battery life.

For years, iPhone users would have to manually tweak settings in order to preserve juice. But the new low-power mode does all the work for you. In fact, Apple says the feature adjusts settings you didn't even know you had.

For example, it blocks apps from loading data in the background, stops the Mail app from receiving new messages, slows down the processor, and turns off some animations, all so you can get a little extra time out of your charge. You'll still be able to use your phone for most tasks, though.

If low-power mode isn't your thing, iOS 9 has also been optimized to use less power overall. Apple says the typical user will get about an extra hour of battery life just by installing iOS 9.

An unfinished beta version of iOS 9 is available now. If you have it, here's how you turn on low-power mode. First, open your settings app.

Go to the battery section.

Flip the switch next to "Low Power Mode" to green and tap "continue" when you get the warning.

The battery icon will turn yellow so you know you're in low-power mode. Now hurry up and find a charging cable.