Powersave while AC adapter unplugged

By default, when you unplug your AC adapter, cpu scaling governor is not changing to powersave. It’s because Ubuntu using powernowd cpu frequency manager. And to fix this we need to install cpufreqd. Then open /etc/cpufreqd.conf for editing with root privileges (e.g. Alt+F2 gksu gedit /etc/cpufreqd.conf) and put this lines (it’s configured for my P8400 cpu):

# this is a comment
# see CPUFREQD.CONF(5) manpage for a complete reference
#
# Note: ondemand/conservative Profiles are disabled because
#       they are not available on many platforms.

[General]
pidfile=/var/run/cpufreqd.pid
poll_interval=2
verbosity=4
#enable_remote=1
#remote_group=root
[/General]

[Profile]
name=Performance High
minfreq=800000
maxfreq=2267000
policy=ondemand
[/Profile]

[Profile]
name=Performance Low
minfreq=800000
maxfreq=1600000
policy=ondemand
[/Profile]

[Profile]
name=Powersave High
minfreq=800000
maxfreq=1600000
policy=powersave
[/Profile]

[Profile]
name=Powersave Low
minfreq=800000
maxfreq=800000
policy=powersave
[/Profile]

##
# Basic states
##
# when AC use performance mode
[Rule]
name=AC Rule
ac=on                    # (on/off)
profile=Performance High
[/Rule]

# stay in performance mode for the first minutes
[Rule]
name=AC Off - High Power
ac=off                   # (on/off)
battery_interval=70-100
profile=Performance Low
[/Rule]

# conservative mode when not AC
[Rule]
name=AC Off - Medium Battery
ac=off                   # (on/off)
battery_interval=30-70
profile=Powersave High
[/Rule]

# conservative mode when not AC
[Rule]
name=AC Off - Low Battery
ac=off                   # (on/off)
battery_interval=0-30
profile=Powersave Low
[/Rule]

Now, when you unplug your AC adapter, cpu will work in powersave mode with frequencies from 800MHz to 1.6GHz and when battery is below 30% it will stay at lowest frequency value of 800Mhz.

And if you plug adpater back, frequencies will be from 800Mhz to 2.27GHz.

P.S. If you have found some decrease in performance or gui response, just reinstall powernowd.