This activates when the phone’s battery levels drop below a certain percentage. Alternatively users can opt to turn it on whenever they want through the Settings menu. So how does it work? Basically low power mode reduces the performance of your phone so that it does not need to be running optimally all the time, and thanks to a Geekbench 3 test, the performance levels have been revealed.
As you can see in the screenshots above, the screenshot to the left shows the iPhone 6 Plus running normally. The screenshot to the left shows what happens when low power mode has been activated and as you can tell, performance on multi-core will see a huge decrease of more than 1,000 points, while single-core’s scores only show a difference of 600 points.
The huge reduction will obviously not be good for running certain apps but when you’re low on battery, perhaps that might not be a good idea either way. Low power mode on iOS 9 is expected to extend your phone’s battery by about 3 hours although your mileage might vary depending on what you do with it during that time.