Today I tested how long my laptop’s battery can last when I just keep it on the table, idling. Running Linux and a bunch of applications, the TFT set to the lowest brightness setting. Wireless activated.
After the laptop switched off, I plotted the power consumption curve with gnuplot, which I wanted to get to know for a long time already 😉 The data file (fed from /proc/acpi/battery/BAT1/state) contained 1678 data points (ten samples per minute). The gnuplot session looks like this:
gnuplot> set terminal png picsize 800 600
Terminal type set to 'png'
Options are 'small color picsize 800 600 '
gnuplot> set output "test.png"
gnuplot> plot "powerlog3" using 1:2 title 'Power consumption (W) over time (min)' with lines, "powerlog3" using 1:3 title 'Remaining (%) over time (min)' with lines smooth unique
You can see the result here:
In the beginning I finished something I was working on, so you can see some spikes in the power consumption when I launched programs and such… After 60 minutes the monitor switched off, so the consumption drops. I guess I hit the table at minute 144 or so, because then the monitor seems to have switched on again, don’t remember though 😉
I’ll do the test running Windows at a later time – but there I will only get one number – the total runtime. I have no idea how I could get statistics like that in Windows, and I’m not willing to try 10 shareware programs until I get a suitable result 😉
I got around running the test in Windows. I tried to produce about the same conditions: display switches off automatically after 60 minutes, no automatic standby and stuff. I also remembered to switch on the display again after ~70 minutes of being switched off, so the results should really be comparable. One of the apps I kept running on the otherwise idle system was a PuTTY window. Therein I ran a shell script on my server, which touched a file every ten seconds, so I just would have to check the modification date of that file to know when the box went down. I started the test at 11:01 local time, which means 3:01 UTC. The file’s modification date is: 2007-06-11 05:22 (UTC). –> The laptop was shutdown automatically after 2:21h.
So it’s definitely not true that there is some energy wasting going on when Linux is running on a computer, as I have been told (and which eventually caused me conducting this experiment 😉 ). If anything, Windows lost here, as usual.
P.S.: Some information about the two software environments:
Linux: Kernel 2.6.21-gentoo-r2, (for details, have a look at my current configuration). On top of it, running Xorg, KDE with Beryl as window manager, there are usually about 150 processes in the task list.
Windows: Windows Vista Business, everything left quite to the default (I never use it…). No special services running or anything.