Saving laptop power by dimming display

I use a modern HP Compaq laptop for business use.  Recently, I installed Kubuntu 8.10 on it with KDE 4.1.  One of the features of the power monitoring task is that it can tell you how much power your laptop.  Power is measured in watts, just like lightbulbs.

When I’m casually using my laptop, it uses between 16 and 21 watts.  I played around a little with the display brightness controlls, and I found that as much as 25% of the laptop power is used by the display backlight.  When the display brightness is all the way down, my laptop uses 16-17 watts.  When the display birghtness is fully bright, it uses about 20-21 watts.

This means that you can extend the lenght of time that you can run a laptop on a single battery charge by 20-40 minutes by turning the display brightness down.

The environmental impact of this energy savings is not very significant to other home energy saving measures, such as using LED Christmas lighting.

Disclosure: I am an engineer for HP, but I have not worked on designing any laptop systems nor have I done developement on power efficiency.

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