The HTC One (M8) is one of the better Android devices we’ve seen in a long time, but it was missing one key feature. The Extreme Power Saving mode, bragged-up on launch, was absent from US variants of the device. Promising to include it shortly, HTC has made good on their word, and those with an AT&T HTC One (M8) are starting to see it via an update.
The Extreme Power Saving mode is as it sounds, keeping your device sipping battery juice rather than guzzling it. By enabling the power saving mode, you’ll still get basic functionality, but more consumptive services will revert to the background, only drawing juice when prompted.
Say you have messaging client that is always refreshing in the background, but you don’t always need it to. Extreme Power Mode will keep things like calls and texts flowing, but leave everything else quiet until you open it up.
HTC says this can increase battery life by around 40% on average, which we’ll now get a better sampling to prove them wrong or brag about their feature. The update is rolling out over the air, so be on the lookout for a pop-up to prompt you to load it, AT&T customers.
Source: Android Central
So it is basically the same thing as stamina mode on my xperia Lol?