I'm setting up a laptop at home which will act as a file server for when I'm away at school. (offsite backup).

I'm trying to make it run as power efficiently as possible. I need it to be on at all times. The display is turned off. I don't want to shut off any of the cores or turn down the speed because it does other things too.

Is there any benefit in turning off the AC? Such as having it run on AC for one hour, and on the battery for 30 minutes? My dad gave me a timer (one of the ones that you use for a lamp) and told me to see if it would help. I think that it would make it worse because it draws more power while charging because it has to make up for those 30 minutes it ran on battery. That would also hurt the battery too, right?

You are correct in saying that the power lost in the battery will need to be replaced by the power supply during re-charge. So there is no power saved in the long-run. Yes, the battery would begin to develop a 'memory' that would only last 30 minutes, or even less over time. Your dad's idea was a good one; but unfortunately, doesn't help overall.

Keep your processes as low in number as possible, and you should do just fine with the other things you have already done.

Good luck!

OK, that's what I thought. Thanks!

Most consumer electronics these days use Lithium-Ion batteries which do not suffer from memory effects like Ni-Cads did. However, over their lifetime Li-ion as they age will not last as long. Not fully discharging the battery might cause the laptop not to show the battery fully charged which can be fixed by a calibration. Excessive heat is also not good for the batteries. As stated you are not going to save energy in the long run.

It is basically incorrect for power saving. Once you drained the battery, you'd have to recharge the battery. But you have to put in MORE power to recharge it as you originally drained from it. That is called efficiency.

As a matter of fact, I think battery efficiency might be as low as 70%, so in using charge of the bettery and recharging it later, you would use about 40% more energy as when you run the laptop just on AC.

If you have the choice, lower all clock speeds from your processor and graphic adapter. Power dissipation could decrease until 5 Watts or so. You will also dissipate some power in your AC adapter, which might me 3-5 Watts.

In general, everything which gets warm dissipates power, and you never get anything useful back for that. Feel the battery when you recharge it!

jlinkels

Silly as it sounds, leaving your screen/lid open can make a huge difference in cooling on some particularly warm laptop models. Closed lids can trap the heat in, causing the fans to run more often, using more electricity etc. So long as you configure the screen to power off after a certain period of idle time, regardless of whether or not it's actually open, it might help a bit.

If your laptop is a relatively recent Intel-based model, it probably supports some form of Speedstep/automatic CPU throttling depending on the actual amount of CPU needed. A 2.16 GHz Core Duo, for instance, often runs a full Hardy Heron gnome desktop at 1.0 GHz when idle/close to idle, only peaking at the full 2.16 GHz if CPU-intensive tasks such as filesystem or email indexing are running.

Final consideration: you could configure the laptop to boot into runlevel 3 (text-only mode), and change to runlevel 5 when you actually need a GUI/desktop etc.
Sounds like it's only going to provide offsite backup services--you don't need a GUI to run rsync