Energy Saver is one of the features you can find Sleep mode in iOS 9
Sleep mode in iOS 9 Beta. Apple has actually promised to provide a power-saving mode feature that can increase battery life to 1 when the battery reaches its critical value. This storage mode feature is already familiar to Android users, and Apple recently introduced this feature. You can find this function under Settings >> Battery >> Sleep mode. When the power save mode is activated, the color of the battery icon turns yellow. Apple explained the overview of this feature as follows:
Low power mode reduces power and network activity to extend battery life. When this option is enabled, Mail Fetch, Background App Refresh, Motion Effect, and Animation will be disabled. “
Users can enable the power-saving mode for iOS 9 through the system settings or the familiar Low Battery dialog box that appears when the battery of an iOS device reaches 20 percent and 10 percent charge.
Recently, Macrumors has discovered that enabling low-power mode can actually affect the performance of the iPhone processor, as demonstrated by Geekbench 3 for iOS, which was recently updated with support for iOS 9 builds. Geekbench is a benchmark software that is often used quantitatively as a reference for the performance of a single or multi-core processor. They tried to test Geekbench for the iPhone 6 plus, and they found that the performance of the multi-core processor dropped from 2.891 to 1.751, while single-core performance dropped from 1.066 to 1.019. The results on an iPhone 5 were similar, and performance dropped by 40.
At the moment, we can not say “technically” that Apple is extending battery life by sacrificing processor performance, as iOS 9 is still in beta.
It is a matter for a user who is going to play a game. A pop-up message informing you of the power loss should appear in the game when the power saving mode is activated. Apple’s Battery Saver Mode solution should be able to reach all the components that consume the battery, including the processor. But their confusion unfortunately said that the low-power mode “can extend the life of your battery even further.” This statement needs further explanation.