I've been sitting on some power results for a while but by posting them here perhaps more people will see them. This email is quite long and the results are somewhat raw and in no particular order. Rough conclusions are at the end.

Basically I used powertop (to measure draw when on battery with no mains) and a "wall watt meter" (to measure draw through the mains with no battery physically in the laptop) using a borrowed laptop. This was to give me a better idea of what draw to expect under particular conditions. I didn't test especially rigorously but I did try and let readings settle and where I would get multiple readings I would err on the side of least power if I could reproduce the readings or put a range.

Unless indicated otherwise, results here are for a Gutsy Tribe 5 install on the Linux side and an IBM/Lenovo customised Windows XP Professional on the Windows side.

I almost certainly won't do any extra tests as I simply don't have the time (it's been hard enough to get any results as it stands). However others are free to post their results and I happy to discuss what I did to get a particular result.


Linux power usage
(In the following results a heading will continue apply unless overridden by a later heading)

All wake up hog programs killed, laptop mode on, backlight off
powersave governor max
16.5 wakeups per second, 11W
powersave governor ondemand
21.7 wakeups per second, 10.9W
Backlight on at maximum brightness, powersave governor ondemand
20.8 wakeups per second, 13.0W
Bluetooth and wifi on (via soft killswitch)
175.6 wakeups per second, 15.4W
Bluetooth and wifi on, compiz on
240.5 wakeups per second, 15.4W
Bluetooth and wifi off, compiz on
94.0 wakeups per second, 13.1W
Bluetooth and wifi off, compiz off (once AIGLX is turned on your interrupts will seemingly rise until Xorg is restarted)
80.2 wakeups per second, 13.0W
(reboot, default programs running)
Brightness 100%, metacity, wifi on, bluetooth on
231.1 wakeups, 15.5W
Hardware killswitch on
69.9 wakeups, 13.2W
killall thinkpad-keys
51.7 wakeups, 13.0W
55.4 wakeups, 13.1W
kill hald-addon-storage
21.4 wakeups, 13.0W
(could try killing mixer_applet2 but it doesn't seem worth it)
101.4 wakesups, 13.1W
(blinking cursor in vi seems to use up 0.1W)
(reboot) hardware killswitch, killall thinkpad-keys, kill hald-addon-storage, disabled laptop-mode
19.0 wakeups, 13.4W

Linux power usage on A/C
22/23W Playing music over DAAP


Windows power usage
On the Windows side this laptop came with extra tools that seem to allow more sophisticated battery vs speed trade offs. The initial wattage measurements are those reported by the IBM/Lenovo battery tool and are the lowest seen reading.

Idle laptop, default battery settings
9.97W
Starting notepad and typing, default battery settings
14.12W

Idle laptop, optimal powersave battery settings
(this seems to allow the hard disk to still remain constantly spinning but in perhaps in some sort of low power mode)
8.03W
Idle laptop, maximum powersave battery settings
(this seems to allow the hard disk to still remain constantly spinning but in perhaps in some sort of low power mode)
7.93W
Idle laptop, hardware killswitch on, maximum powersave battery settings
7.63W

(Strangely, I found that the laptop would emit a whine while it was powersaving if Bluetooth was on)

Windows power usage on A/C
The following wattage measurements were produced by my wall watt meter.

Idle laptop, wireless off, powersave maximum on A/C disk spinning
16/17W
Typing in notepad, wireless off, powersave maximum on A/C disk spinning
16/17W
Idle laptop, wireless on (connected to AP), powersave maximum on A/C disk spinning
20W
Playing music in iTunes via DAAP, wireless on (connected to AP), powersave maximum on A/C disk spinning
20W
Idle laptop, wireless on (disconnected from any AP), powersave maximum on A/C
18/19W
(It is worth noting that the IBM/Lenovo Windows wireless software tries hard not to remain in scanning mode)
Playing a 3D game with sound, wireless state unknown, powersave maximum on A/C
23-25W

Conclusions
At least on Linux (but I'd imagine these apply to other OSes too) there are some things you should try and do first as these seem to yield the biggest savings. I've ordered them with the items in descending order here:
Disabling wifi and bluetooth - 2.4W!
Dimming the screen - 2.1W
Turning on laptop mode and let the disk idle - 0.4W
compiz on AIGLX hit - 0.1W if it's not being masked by something else. Wakeups need to be at the 80 or below mark to see the difference in power draw (e.g. having wifi and Bluetooth on will mask the effect on turning compiz on)
As mentioned elsewhere on the web using the ondemand governor may result in less power usage than maximum throttling.

The minimum draw seen under Linux while idling in X was 10.9W (wifi and bluetooth disabled, screen maximally dimmed, thinkpad-keys killed, hald-addon-storage killed, mixer_applet2 killed).

Using operating system reported figures, the lowest I saw Linux go was 10.9W when idling. The lowest I saw Windows going when idling was 7.63W. Even looking at A/C power usage via the wall plug watt monitor, Windows seemed to be able to go use 20W while playing sound and using the wifi whereas linux seemed to only go as low as 22W.

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Sitsofe | http://sucs.org/~sits/