Seems HTC has made a tiny boo-boo in their One X software, which causes the battery on their new flagship to drain a bit more than it should. Luckily, XDA developer mike1986 has discovered the issue while working on a custom ROM for the device and has released a method for fixing the problem, with some users claiming an increase of 10%-20% in battery life.
Apparently, an app known as NvCPLSvc.apk was placed in the /system/bin directory on the phone, but it actually belongs in the /system/app directory. This one little slip-up caused the Tegra 3 power management software to not work properly. The fix is to move the file to the proper directory and change the file’s permissions appropriately. This can all be done using ADB to push the file to the right place on the handset, or by using a root-aware file explorer on the device to move the file and change the permissions.
Or, if you don’t want to root, you can wait for HTC’s official fix, assuming HTC includes the fix with the next update.