While Microsoft is expected to address all these issues in the final version of the OS, it turns out that this kind of bug can be fixed in a pretty unexpected way.
A Microsoft support team member has provided more details on this:
“Powercfg /sleepstudy reports any issues that are preventing the CPU from entering its lowest power state during Connected Standby (e.g. screen is off). In this case, the state of the specific UART controller is preventing the CPU entering its lowest power state. This UART happens to be connected to the Bluetooth radio on Surface. Unfortunately, the bug that causes this bad state occurs exactly when the Bluetooth radio is turned off in PC Settings.”
If you’re one of those experiencing battery issues after making the switch to Windows RT 8.1, make sure you turn on Bluetooth as soon as possible.
Here’s how one of the affected users describes the problem:
“Since installing the Windows RT 8.1 Preview I have experienced high battery drain in Connected Standby. I'm losing 2-3% an hour when the Surface RT is in standby, so losing 30% battery during the day when not being used.”
To do this, swipe left from the right side of the screen to launch the Charms bar, tap on “Settings” and go for “Change PC Settings”. Open “PC and Devices,” go over to “Bluetooth” and turn it on.
Of course, the bug is to be fixed in the RTM version of Windows RT 8.1, so more details on this are expected to be provided later this month.