My monitor, or my X version, or my Xorg drivers, or my KMS kernel, or my xscreensaver version, or my goldfish has a broken DPMS implementation, so that my monitor doesn't turn of when idle. This is a particular waste of energy during the night. Luckily my monitor responds correctly to xset dpms force off when issued twice with a small delay. Using xprintidle-ng , I can work around the problem. #!/bin/sh ACTIVATE=$(expr 60 \* 1000 \* 45) # sleep after 45 mins. LASTIDLE=0 while sleep 60; do IDLE=$(xprintidle-ng) if [ "$LASTIDLE" -lt "$ACTIVATE" -a "$IDLE" -ge "$ACTIVATE" ]; then xset dpms force off sleep 10 xset dpms force off fi LASTIDLE="$IDLE" done