"Now in iOS 9 we give you a single switch in what we call Low Power Mode and it pulls levers you didn't even know existed and is able to extend battery life for an additional three hours of typical use on top of that additional hour."
With Geekbench 3 updated to support iOS 9, MacRumors was able to benchmark an iPhone 6 Plus running with Lower Power Mode on and off.
Without Low Power mode activated, an iPhone 6 Plus scored 1606 on the single-core processor test and 2891 on the multi-core processor test. When Low Power mode was turned on, the same iPhone 6 Plus scored 1019 on the single-core test and 1751 on the multi-core test, suggesting there's a significant performance reduction when Low Power mode is enabled to save as much battery as possible.
Results on an iPhone 5s were similar with performance reduced by about 40%.
Users are prompted to enable Low Power Mode when an iPhone drops to 10 or 20 percent battery level and it can manually be enabled from the Battery section of the Settings app.
Apple will release iOS 9 to the public this fall. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.