Comment 5 for bug 194732

fyi...i had this exact same problem running ubuntu 14.04.

the monitor powersave function would work fine when sitting at the machine and interacting directly with it. when i'd step away, the monitor would power-off as expected.

but when i would interact remotely via VNC (desktop sharing) and stop using the machine, the workstation's monitor would stay on indefinitely regardless of the powersave settings.

this undesired behaviour was consistent whether i was using xfce-power-manager or light-locker to manage the monitor powersave settings.

but when i tried xscreensaver instead (after removing both xfce-power-manager and light-locker), it worked fine -- the monitor powersave would activate whether i was working directly with the machine or accessing remotely via VNC.