Some quick power consumption testing with a "new to me" tablet


The Lenovo I had been using has given up the ghost.  The hard drive in it has physically died – it won’t boot, nor pass the BIOS diagnostics.  I now have managed to get assigned a Fujitsu Lifebook – a “hand-me-down” from another tester who no longer needs it.  It’s pretty nice so far, but I am not looking forward to learning yet another keyboard layout.  Seriously, why no two companies can decide where to place keys is beyond me.  And on this tablet, the CAPS LOCK key is the second largest key on the keyboard. 


One of the last tests I did with the Lenovo before it died was hook it up to a Kill a Watt meter to see how much power it used.  While booting, with full screen brightness and the hard drive running, CPU at 100%, the tablet pulled 35 watts or so.  Not too bad relative to the a desktop.  As a single point of reference, both a 19 inch flatscreen and a 19 inch Energy Star CRT monitor need 60 watts.  I was not truly testing power consumption at this point.  I was just seeing what the device needed.


The Fujitsu arrived and I decided to hook it up the same way.  I expected similar results, but the Lifebook  needs about 45 watts on average, and can bump up to 55 at times.  Some of that much higher result is because the Lenovo did not have  a CD player and the Fujitsu does.  As it sits idle now, with only a full brightness screen, it uses 21 watts.  Turning the screen down to the most dim setting at which I can still see it, power consumption falls to 17 watts.  Not too bad for a dual core notebook.


Now here’s the real geeky bit.  I run GIMPS at home 24 hours per day.  I have a single core dekstop running it, and the CPU stays at 100% load.  I’ll spare you the math, but with GIMPS running, my power bill here in the Seattle area goes up about $56 per year.  It would be quite interesting to see how much each tablet would cost in electricity per year, but I’m sure each manufacturer would come up with a typical “user scenario” that benefitted its line of tablets. 


The OneNote 2007 team tested power consumption pretty well too.  If you look in Tools | Options | Other, you will see a battery settings dropdown.  This controls the search indexer, which in turns uses the hard drive.  Since most modern laptops will stop spinning the hard drive (due to its power consumption) unless it is needed, we let you control whether you want the indexer to run.  If you have many audio recordings, the index can take quite a while to be developed.


Questions, concerns, comments and criticism always welcome,


Comments (5)

  1. Pep says:

    Wow, I leave my laptop plugged in and turned on 24/7. I wonder how much power I am using. I thought about getting one of those KillAWatt things, but was afraid of what it might reveal!

    Anywho, I just got my husband a used TC1100 and I love it. It is our first tablet PC and I don’t think it will be our last! Are you going to replace your hard drive or just get an entirely new TPC?

  2. JohnGuin says:

    Hi Pep,

    No, no new PC.  I managed to hook the SATA drive to a desktop I had and booted.  Running scandisk on it resulted in 118 errors, all fixed.  I put the drive back in the Lenovo and booted.  Its startup procedure found another dozen errors and bad sectors.  A few files had been corrupted, and a simple copy of them allowed the thing to boot.  I have no faith in the drive, but don’t want to spend more of our hardware money on another tablet.  I’ll keep using this one until the hard drive completely dies.


  3. hoper says:

    As I told you my desktop PC hard drive die too, I do almost the same, but on every boot I have a new currupted sectors and the PC reboots before login :P, I get use to have 2 logical partition, one for Windows and program files and other for my documents (if I need to reinstall everything just format the first one) and the problem seems to be related with the last one 🙁


  4. Freek says:

    You mention power settings in the OneNote options. Really Great! However, would it not be proper to have this setting in the Vista Power Plan options too? That way you can distinguish between running on battery and plugged in.



  5. JohnGuin says:

    Thanks for the suggestion, Freek!