The Impact of SSD on Battery Life

One advantage of solid state storage is lower power consumption thanks to not having any motors or moving heads to drive; spinning anything 4200 times a minute is going to be more power hungry than a solid state solution. The SSD vs. mechanical HDD power debate would normally be a clear cut one but we're comparing to one of the lowest power HDDs on the market here.


Power Consumption 80GB 4200RPM HDD 64GB SSD
Read/Write 0.9W 0.24W/0.36W
Idle 0.30W 0.035W
Standby 0.07W 0.035W
Sleep N/A 0.015W


The power savings are dramatic; idle power is reduced by nearly a factor of 10, standby power is cut in half and read/write power is at worst a third of the mechanical drive. The 10x idle power reduction is important since that's where your drive should be spending most of its time, and if the average power savings is somewhere in the 0.25 - 0.5W range you're looking at improving battery life on the order of tens of minutes.

To find out the impact on battery life we ran through three different scenarios:

I scripted together three tests: wireless web browsing, DVD playback and a multitasking workload.

The wireless web browsing test uses the 802.11n connection to browse a series of 20 web pages varying in size, spending 20 seconds on each page (I timed how long it takes me to read a page on Digg and came up with 36 seconds; I standardized on 20 seconds for the test to make things a little more stressful). The test continues to loop all while playing MP3s in iTunes. This test is designed to simulate the intended usage of the MacBook Air: something you can carry around with you to class, work, on the train, etc... to comfortably and quickly browse the web, take notes and generally be productive all while listening to music. It's like a big iPhone...without the phone part.

Despite the lack of an internal optical drive (I've never been so tempted to use the f-bomb in a review before), the MacBook Air will play DVDs. You just kind of need to have them on your hard drive and I'll just assume you have the original disc safe at home. This test is simple: I play Blood Diamond in a loop until the battery runs out.

The final test is the multitasking workload, and this test isn't really that intensive for a normal system but thanks to the terribly slow iPod hard drive in the Air - it's quite stressful. For this benchmark I'm downloading 10GB worth of files from the net (constant writes to the drive), browsing the web (same test as the first one) and watching the first two episodes of Firefly encoded in a 480p XviD format (Quicktime is set to loop the content until the system dies). There's nothing too extreme about this workload, I could definitely come up with worse - but this would be light to moderate usage on a MacBook or a MacBook Pro, and it'll show how the Air stacks up.

The system was set to never shut off the display and never go to sleep, although the hard drive was allowed to spin down when possible. The display brightness was set at 9 blocks (just over 50%), which I felt was comfortable for both day and night viewing.


Battery Life Test (H:MM) 80GB 4200RPM HDD 64GB SSD % Improvement
Wireless Internet + MP3 4:16 4:59 16.8%
DVD Playback 3:25 3:56 15.1%
Heavy Downloading + XviD + Web Browsing 2:26 2:42 11.0%


As expected, the impact on battery life isn't huge but it's definitely noticeable. With the 64GB SSD installed we're actually able to hit Apple's 5 hour battery life claim with the MacBook Air. Our wireless browsing test actually saw the biggest improvement in battery life, increasing a full 43 minutes from a simple drive swap.

The DVD playback test got the next largest boost of 31 minutes or 15.1%, followed by the multitasking scenario that saw a more meager 16 minute increase in battery life.

With an average increase in battery life of 30 minutes, you're paying an extra $33 per minute of battery life based on present day SSD upgrade pricing from Apple. If you look at it that way, the improvements stop being as exciting - but the takeaway point is that the technology is useful and down the road, when SSD prices drop, you can look forward to an upgrade that does improve the overall experience.

MacBook Air Performance: SSD vs. Mechanical HDD The SSD Discussion
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  • michael2k - Friday, February 15, 2008 - link

    Fujitsu P7230: Too slow (one core at 1.2GHz vs two cores at 1.6GHz), half as much ram (1GB vs 2GB) for the same price
    Dell XPS 1330: You can't get a 1210 from Dell.com (one pound (33%)heavier) for 2/3 the price
    Sony TZ250N: You can't get a TX from Sonystyle.com, too slow (2 cores at 1.2GHz vs 1.6Ghz), too expensive ($600 more)
    Sony SZ750N: Too big and heavy (1 pound (33%) heavier and twice as thick) for the same price

    You argue against thinner: Thinner is only a measure of weight. Compare to 3 pounds (2.7 to 3.2 pound) and you already eliminate the toughbook, the Dells, the Portege, and the SZ. Compare to the CPU speed and you eliminate the Fujitsu and Sony TZ.

    So what is left? The Lenovo X300, which is still more expensive, but for that extra expense you get an optical drive.
    Reply
  • mattbull08 - Monday, February 18, 2008 - link

    actually a lot less "cool" but a much better option would be a panasonic T5 thicker but lighter than the MBA but with twice the battery life... and that last is really important in something you always carry and use all day, anything which can't go a full day without a charge is just not worth the expense (I know the T5 will do a UK->West Coast flight on a single charge).

    The only real loss is less performance (do you really need it on the road??) and nowhere near as nice a screen.

    Really depends on what your usage is... but I'll get a T5 when my current notebook goes thanks.
    Reply
  • blumenbach - Thursday, February 14, 2008 - link

    "OK, so then the Sony TX, the Fujitsu P7k, the Toshiba Portege, the Dialogue Flybook, the Panasonic Toughbook, the Dell XPS1210, the Sony SZ, The LG XNote."

    The only one in this list that could compare with the MBA is the Portege, and even here it feels and looks like a plastic toy in comparison to the MBA. The display isn't near as sharp or bright on the Portege, and it's much slower. I owned the Sony, and Anand's review is right on: the cramped keyboard and tiny display made it a definite chore to use ergonomically.

    So, yes, just like the MP3 player (iPod) and smartphone (iPhone) Apple has taken the ultralight class, studied what others have done, and have set a new benchmark by redefining what is possible with these devices.
    Reply
  • themadmilkman - Thursday, February 14, 2008 - link

    "Redefining what is possible with these devices?" That's taking it a bit far, and I'm a rabid Apple fanatic. The MBA is a first effort, and just that. I spent a good amount of time playing with one at the Apple Store yesterday, and the only thing I can say about it is that it is simply too large. I can do without the ports, the external drive, the non-removable battery, etc., since none of those things really affect how I use my laptop. But if the MBA were reduced to an 11" or even 12" screen with a slightly smaller bezel around the screen, I would buy one. Until then, it's worth it to just carry the extra two pounds and buy a MacBook. Reply
  • ninjit - Wednesday, February 13, 2008 - link

    Regarding the 8 hour time-to-charge you noticed a few times. Did you calibrate the battery when you first got the Macbook Air.

    I've seen similar behavior on Macbook Pros before, when new or after buying a new battery - and it's almost always because the user failed to collaborate the battery initially.

    It's one of those simple things that manufacturers tell people to do (for good reason in this case), but most ignore.
    Reply
  • Omega215D - Wednesday, February 13, 2008 - link

    I noticed that you missed the page down and page up buttons. I have to say that I like scrolling with the trackpad much better. Place two fingers on it and slide downward makes this a nice feature.

    To me the LED backlighting made the blacks a little richer and less prone to showing bleed like the regular LCD on the MacBook, did you feel this way too? I wished that LED backlighting is available for the regular MacBook like the one I just bought.

    I like the way Apple did keyboard lighting on the Air than the one on the MacBook Pro. Black keys with lighting works much better than lighting on silver keys in my opinion. This being said I get by just fine using the light from the screen to illuminate my keys.

    On a final note, there's no need to miss the right click button on the track pad, I just set the pad to accept clicks and allowed for two finger tapping to be a right click. I find it pretty difficult to go back to other laptops.
    Reply
  • Omega215D - Wednesday, February 13, 2008 - link

    I noticed that you missed the page down and page up buttons. I have to say that I like scrolling with the trackpad much better. Place two fingers on it and slide downward makes this a nice feature.

    To me the LED backlighting made the blacks a little richer and less prone to showing bleed like the regular LCD on the MacBook, did you feel this way too? I wished that LED backlighting is available for the regular MacBook like the one I just bought.

    I like the way Apple did keyboard lighting on the Air than the one on the MacBook Pro. Black keys with lighting works much better than lighting on silver keys in my opinion. This being said I get by just fine using the light from the screen to illuminate my keys.
    Reply
  • bpurkapi - Wednesday, February 13, 2008 - link

    When I first heard rumors of the Air I was excited. But seeing that there is no opportunity to upgrade it is worthless to me. For $1800 the ability to upgrade should be standard. This makes me really enjoy the smaller and more affordable EEEpc. If the purpose is just basic internet and note taking the EEE is a much better choice for a college kid, then the overpriced Air. I see the air as a status notebook, at 13.3 it is not really an ultra portable, yes it is light but the form factor is not that portable. I believe the size of the EEE is about as small as one can go without serious drawbacks. I think the Air will sell like the iTV. I just wonder why Apple would release this subpar product following the iPhone? You would think it would have been a tablet and actually had a smaller form factor. As of now the Air is worthless compared to other portables. Why would anyone buy this when the Macbook has better specs and is only 2 pounds more. The thinness of the Air is a gimmick and really doesn't provide much more portability. Reply
  • Griswold - Tuesday, February 19, 2008 - link

    But its a clear winner! This is why:

    http://www.abload.de/image.php?img=macbookcommodor...">http://www.abload.de/image.php?img=macbookcommodor...
    Reply
  • Mathue - Thursday, February 14, 2008 - link

    ""EEEpc. If the purpose is just basic internet and note taking the EEE is a much better choice for a college kid""


    I dunno, the EEEpc is way too small. In my job on the road, field and office I need a light machine that has REAL keys. My fingers are large since I do actually do 'work' in addition my eyesight isn't what it once was. The tiny screen on the EEEpc might as well be an iPhone with the text size. And for heavens sake, if the 'Surf' EEEpc has a RAM slot, darn-it, put a door on it so you don't have the pull the machine apart! I also, much as I dislike it, must have perfect Word, Excel and Powerpoint compatibility, (Watching a colleague running Ubuntu on a Thinkpad July of last year for a pre-made company presentation was painful) the OEM linux 'office like' application doesn't give me that, at least there is office on the Mac. And don't say run XP on one of those, I deal with enough XP foibles as it is then to have to run it on a 7" screen with cramped keys. As it is the Air probably barely fits for me, but the EEEpc just goes way too far size wise and is even less of use.
    Reply

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