Apple's next big iPhone update will turn your iPhone 6 into an iPhone 5/5s to save battery life

Apple's next big iPhone update comes with a feature that helps you get the most out of your iPhone's battery, especially when it's already running low on juice.

Naturally, this means your iPhone has to cut back on some of its normal functionality to conserve power.

New tests run by blog MacRumors show us just exactly how much this low power mode dials back your iPhone's performance.

MacRumors used GeekBench, a popular tool used to measure how a smartphone's processor performs, to conclude that low power mode reduces performance by about 40%. This means your iPhone 6 would be on par with an iPhone 5s or iPhone 5 in terms of performance, as 9to5Mac points out.

If you turn on the feature, your iPhone will automatically kick into Low Power Mode when it's nearly out of battery. Your iPhone will cut back on background activity, such as fetching email, automatic downloads, and visual effects such as the parallax wallpapers.

It seems like a welcome trade-off though - during its annual developers conference keynote earlier this month, Apple said Low Power Mode in iOS 9 can extend your iPhone's battery life by three hours.

Adding new features like this is important for both iPhone and Android. In general, battery technology for smartphones hasn't really advanced dramatically in the past several years. So it's up to the companies making software for smartphones to make sure their operating systems are optimized to get the most out of these batteries.