It does not sound good but this is the real fact. If you have a Microsoft Surface RT device with Windows 8.1 Preview installed and facing issue with battery consumption while in standby mode, it’s time for you to turn ON the Bluetooth of your device.
Microsoft support team answered in a forum thread that it is a bug and the current solution to resolve the quick draining of battery is to turn on the Bluetooth.
This is definitely a strange solution but works for me too. If you have installed Windows 8.1 Preview in your Surface RT and noticed that the battery is draining quickly than the expected period, it’s due to unnecessary power uses by different parts of the system. In a forum thread, Microsoft support team provided a workaround to resolve this problem until the next/final build of Windows 8.1 comes up.
As an answer to the thread, he asked the user to turn on the Bluetooth radio signal which actually increased the battery backup of him. I also tried the same in my Surface RT and noticed the issue got resolved. So, what’s the reason behind this? In general, keeping the Bluetooth signal on should eat more battery but in this case it’s different. Let’s read the answer to this question from the support team itself:
Powercfg /sleepstudy reports any issues that are preventing the CPU from entering its lowest power state during Connected Standy (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.
It is reasonable to want to turn off the Bluetooth radio to conserve even more power, but be aware that the major contributor to drain on battery is overall system power use, not just an individual radio.
As Microsoft is aware of this bug, we could expect the fixes quite soon in the next or final build of the Windows 8.1. Till then, if you are facing battery backup issue during standby mode of the Surface RT device, turn on the Bluetooth signal and notice how it effect the power consumption.
How to Turn ON the Bluetooth signal?
To turn ON the Bluetooth, swipe in from right to bring in charms bar, tap on Settings and then on "Change PC Settings" at the bottom. Subsequent steps to get to the switch to enable Bluetooth: Change PC Settings -> PC and Devices -> Bluetooth.
More Resources to read: