If you absolutely have to make your Windows tablet battery last as long as you can, then knowing what drains its power will be very helpful. That's what Microsoft's new Sleep Study tool can do: generate a report of which apps and activities consume the most energy. Unfortunately, there's a catch -- it only works if your device is in InstantGo sleep mode. InstantGo, a feature for Windows 8.1, was previously called Connected Standby for Windows 8 and RT. Unlike other similar modes, it allows your system to sleep while updating apps in the background and keeps the device in a state that's quickly ready to resume.
Take note that it's not available on all Windows 8.1 devices, so to know if you have it, launch the command prompt and type in "powercfg /a." If you see that "Standby <Connected>'s" available, then you can follow Microsoft's instructions on the Windows Experience Blog to run Sleep Study. The tool will generate the report as an HTML file, where you can see the top five reasons why your tablet's always out of battery when you need it the most.
Microsoft Windows 8.1