Less watts: environmentally friendly, longer lasting battery, less spending on energy bills.
Thanks to these tips you’ll be able to improve your Ubuntu GNU/Linux laptop lasting, maximize battery lasting and life and also our own planet Earth life expectancy!

QUESTA GUIDA È ANCHE DISPONIBILE IN LINGUA ITALIANA

Just for reference on my HP Pavilion dv6500 series laptop I managed to get battery lasting to 3h average @ ~13Watts with kernel 2.6.24 applying the sysfs fixes only typing/reading with wireless on, screen 60%, desktop effects, laptop-mode enabled BUT NO hard disk spin down / powersaving features enabled.

A relevant gain which can be further increased (I managed to get as low as 8,5Watts by enabling hard disk power saving features in laptop-mode.conf. Notice it was not spin down but only powersaving!)

Check http://lesswatts.org for further tips on how to save energy, money and life expectancy!

Note: unless specified following tips will NOT DEGRADE your system performance since they work on demand and will activate only when your system has little load.

Note2: as Harry suggested, do not leave any empty line in sysfs.conf file.

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1. With Laptop-Mode-Tools (great set of scripts coded by Bart Samwel) you get the chance to tweak the following power related features:
   in /etc/laptop-mode/laptop-mode.conf

• Hard Disk related settings: readahead, cache, realtime, powersaving, spindown
• Cache related settings: dirty ratio, etc.

  while in /etc/laptop-mode/conf.d/

• AC97 powersave
• Bluetooth powersave
• Logging files tweaking
• Syslog tweaking (through command lm-syslog-setup)
• CPU frequencies and governors (however Ubuntu has already Gnome that does this)
• Display dpms standby (however Ubuntu has already Gnome that does this)
• Display brightness (however Ubuntu has already Gnome that does this)
• Ethernet disabling (NOTE: autosensing even with AC doesn’t currently work for me)
• Hal polling
• Intel SATA link power management
• Scheduler power saving settings
• Video-out
• Wireless Intel IPW and IWL drivers powersaving features
• Start/Stop of programs and services on power source toggling (i.e. cron, crontab, cups…). These can be set through command lm-profiler

  To enable laptop-mode-tools you have to edit both
  /etc/laptop-mode/laptop-mode.conf
  and (if you use the package from the repositories) also
  /etc/default/acpi-support

  You may consider updating laptop-mode-tools from intrepid repositories. These have a new version which has more comprehensive power tweaking options:

  http://packages.ubuntu.com/intrepid/laptop-mode-tools

  NOTE: I advise against using the package provided from laptop-mode-tools maintainer website http://samwel.tk/laptop_mode/ since that wouldn’t resume its functionalities upon resume from suspend/hibernate. The package from the repositories, instead, provide a set of scripts for it to be always checking the power state (AC or Battery powered).

  The aforementioned scripts are available here: /usr/lib/pm-utils/power.d/laptop-mode and relies on the new pm-utils framework.

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2. Enable Ethernet network CPU offloading (click here for the howto)

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if USB autosuspend is enabled at the kernel level there is no more need to tweak these settings, also because powertop reports them not being active and consuming power while not working.

# manage suspend of Authentec Fingerprint Scanner.
# Bus 004 Device 003 AuthenTec, Inc.
# timeout time (seconds)
bus/usb/devices/4-1/power/autosuspend = 2
# power level: on = always on; auto = autosuspend; suspend = always off
bus/usb/devices/4-1/power/level = auto

Note on USB devices addresses: to locate the USB device address in /sys you first have to ‘lsusb’ then keep in mind the ‘Bus 00N Device 00N’ relative to the device you want to manage. Go into /sys/bus/usb/devices and here look at the entries in this form X-Y (numberDASHnumber) and use ‘cat X-Y/busnum’ and ‘cat X-Y devnum’ in order to identify the correct device.
With this in mind you can apply this tweak to every USB device attached to your laptop (however it makes sense only for those embedded into the laptop (fingerprint, webcam, bluetooth), not the external ones).

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Enable low power state for Realtek HDA audio switch
(integer express idle seconds after which to power off the device)
note: audio led will toggle blue/amber according to active/powersaving state

Add the following line in /etc/sysfs.conf

module/snd_hda_intel/parameters/power_save = 10

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in /etc/X11/xorg.conf (your video configuration file) enable  on demand V-Blank (which will reduce by 60 your kernel wakeups). This works for nvidia cards with nvidia 3D propietary driver.
under section “device” add following string:

Option “OnDemandVBlankInterrupts” “true”

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if you use GNOME you can add to the pannel a very useful applet, the LCD Brightness applet. This enables you to tweak the display brightness according to the environment light and your desired comfort/battery lasting.

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Gnome-power-manager has an interesting feature that allows you to dim screen brightness upon idle status. However you may only tweak the idle timeout from the registry with gconf-editor

run this application in ALT+F2 window and search for

/apps/gnome-power-manager/backlight/

tick enable
set brightness % when idle in idle_brightness
set the number of seconds after which to consider the computer idle in idle_dim_time

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