I’ve been playing around with powertop trying to reduce power usage. I’m using laptop-mode to spin down the disk when its not needed (it automatically activates when on battery power). I’ve also added these two powertop suggestions to /etc/rc.local

# Reduce the frequency of disk flushes
echo 1500 > /proc/sys/vm/dirty_writeback_centisecs
# Turn off the SATA link whenever possible
echo min_power > /sys/class/scsi_host/host0/link_power_management_policy

I’ve also enabled CPU frequency scaling. If I dim the brightness, the laptop uses around 16W of power under light usage: amarok playing in the background and browsing the tubes. It guesses this will give around 3 hours battery life. Not sure if I can make it better…