Ok, so I solved this issue today (and hopefully at least some of you will solve it too). My SP3 (i5/256) suffered from high battery drain while in connected stand-by. Moreover, the total battery life of the tablet sucked, it lasted like 4.5 hours while my SP2 lasted at least 7 hours with light usage. It also charged slower than I thought it was nomal, compared to my old SP2. Although when running "powercfg energy" from an admin command prompt the generated report was looking quite good, when running "powercfg sleepstudy" from an administrator command prompt, in the resulting HTML report I always got the information that the device "USB xHCI Compliant Host Controller" was active 100% of the time and the battery drain was listed at about 4.5-5.5% per hour. A large part of the report was red-colored stuff telling me that something isn't right. In short, the problem was the Type Cover 3 keyboard which did not have an updated firmware (I don't know a way to display the current firmware of the type cover 3). To find out if this is the issue for you, remove the type cover, restart the tablet and then put the tablet to sleep for at least 15 minutes (it seems that it does not register sleep times lower than 12 minutes or so). Then run the "powercfg sleepstudy" from an administrator command prompt and if it looks good (green or orange report section colors and no "100% active" from the USB xHCI Compliant Host Controller) then the type cover is the issue. In order to manually install the type cover latest firmware: - Go to http://www.microsoft.com/en-us/download/details.aspx?id=38826 - Download the "Surface Pro 3 - November 2014.zip" file or whichever is the newest zip for SP3. - Extract it, go to subfolder "\Microsoft\SurfaceTypeCoverV3FwUpdate", right click on the inf file and choose "Install". A reboot will be requested. - Do a sleep study again (min. 15 minutes) to see that the problem is solved. Hopefully this helps some people. If the type cover is not the issue (do the test above) then uninstalling Skype could also solve the problem related to USB xHCI being 100% active during sleep, according to some user reports. Some people reported that a Windows "refresh" also solved this problem. This makes sense, because after a Windows refresh the Windows Update service does all the updates again and brings the firmware of all the various hardware components (including the Type Cover 3 firmware) to the latest versions - or at least attempts to do this. But a Windows refresh also wipes all of the installed software, so a manual firmware update is much simpler. PS: I cannot assume any responsibility for any issue caused by following these instructions.