Wandering Thoughts archives


What seems to use power on an Asus Eee PC

Courtesy of having an Eee around and being curious about how to maximize the battery life, here are some measurements about what bits seems to use how much power. All of these measurements are for a '4G Surf' model; your mileage may vary on other ones.

First, a disclaimer: all of these measurements are made with a power meter while the Eee was on wall power. It's possible that the Eee behaves differently when running on battery power (although I would be somewhat surprised).

Suspended to RAM 3 watts
Minimal powered up state 10 watts
Screen +1 watt (dimmest) to +3 watts (brightest)
Wifi +1.5 watts
100% CPU usage +2 watts
Ethernet no extra power usage

(My power meter only reads to whole watts, and wifi off to wifi on measurements fluctuated between +1 watts and +2 watts, so I am guessing around 1.5 watts for it.)

Or in other words, the Eee draws between 10 watts (if left idle) and 14 watts (screen at full and the wifi active); you can push it to 16 watts if you try hard. This is particularly impressive given my previous numbers; in normal use, the Eee is drawing about half of what one of my Dell LCDs does, never mind the system that they're connected to.

The best non-disruptive thing for power saving is to power down the screen; you can do this with 'xset dpms force off' in a shell. Suspending will save a lot more power, but it will also probably wind up disconnecting you from any ssh sessions and so on, and tapping a key is faster than resuming from suspend.

(Powering the screen down will also make it less likely to distract you during meetings.)

Also, the Eee draws 2 watts when simply plugged into the wall while powered off. This is not the little AC adapter itself, which the power meter says uses no power when disconnected from the Eee. I now disconnect the Eee from the power cord when it's just powered off; if nothing else, it keeps the AC adapter from warming up.

linux/EeePowerConsumption written at 23:54:04; Add Comment

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