If you updated Surface RT from Windows RT 8.1 Preview to Windows RT 8.1, you may notice a decrease in battery life. During the update, the wireless adapter power policy isn’t migrated. Instead, the power policy is set to a default value that consumes more power both during use and in the connected standby state.
To restore the wireless adapter power policy to the correct settings, open an administrator command prompt:
Step 1: Swipe in from the right edge of the screen, and then tap Search.
(If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, and then click Search.)
Step 2: In the search box, enter command prompt.
Step 3: Touch and hold (or right-click) Command Promptto bring up the context menu. Tap or click Run as administrator.
Step 4: On the User Account Control dialog box, tap or click Yes.
Step 5: At the Administrator: Command Prompt, enter the following:
powercfg -setdcvalueindex SCHEME_CURRENT 19cbb8fa-5279-450e-9fac-8a3d5fedd0c1 12bbebe6-58d6-4636-95bb-3217ef867c1a 3
Step 6: Then enter
powercfg -setactive scheme_current