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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  • Brau - Thursday, February 14, 2008 - link

    "The SuperDrive won't work on a regular USB port as it draws too much power"

    Wrong. The MBAir Superdrive uses standard voltage and draws a normal 500ma of current. (See AppleInsider indepth MBA review). Apple has apparently simply chosen not to provide the driver that would allow this drive to work on other Macs, as it will still show up as a USB drive but can't be used. What remains to be tested is whether the MBAir Superdrive can even be used to import a burned CD/DVD on another MBAir once it has been initiated to a first machine. If it fails this test then it would indicate hardware based authentication ala Microsoft & Vista.
    Reply
  • Anand Lal Shimpi - Thursday, February 14, 2008 - link

    You are correct - it looks like the power draw is identical to any other USB optical drive. I don't see any indication of any hardware based authentication tied to the drive, although I haven't specifically tested it.

    Take care,
    Anand
    Reply
  • Brau - Thursday, February 14, 2008 - link

    Wow. Thank you very much for looking into it. IF you do get a chance to test out the drive on another MBA, I'd sure like to know the result. I'm really hoping they haven't invoked any limitations similar to Remote Disk under the assertion that people could use it to share media content.

    Cheers,
    Brau
    Reply
  • Xenoterranos - Thursday, February 14, 2008 - link

    Bravo Anand. I loved the review, and it reminded me of why I started reading Anandtech in the first place.

    I honestly couldn't care less about the Macbook Air, but the review was top notch.
    Reply
  • mlambert890 - Thursday, February 14, 2008 - link

    So Anand...

    Seriously.. the Mac koolaid is making you drunk.

    Youd be "blown away" if Dell and Gateway took away the removable batteries from their existing thin and lights (they dont make ultraportables, and neither does Apple), made them thinner, and removed a bunch of ports and the optical drives?

    Were you "blown away" by the Sony X505? Or how about any of the MANY PC based notebooks that are a LOT smaller and lighter than the MBA?

    I guess not. They're not that nice white color with the Apple logo and arent held up by Jobs at the Mac expo.

    Are PC guys really getting THIS desperately bored that now we're going to join the flocks swooning over any crap Apple chucks into the marketplace?

    At least be honest man. If the MBA had a Dell or Gateway logo you would TEAR IT APART for lack of ports, too large of a footprint, weight that was mediocre since there is a BIG list of sub 3lb PC notebooks and.... NON REMOVABLE BATTERY.
    Reply
  • mlambert890 - Thursday, February 14, 2008 - link

    Not to be picky but, well, *PC* reviews are always picky. There is NO WAY the MBA is an "ultraportable"

    Its HUGE in terms of the dimensions that mean something - LxW. It is a THIN AND LIGHT.

    Im typing this on a Fujitsu P1610. THAT is an ultra-portable - 9.1x6.5x2.2lbs

    13x9 is massive. My Sony SZ had similar dimensions and I couldnt open it in a cramped coach seat on a plane.

    People keep talking about how "the MBA is for special people - you dont get it". MANY of us *do* "get it". There are ALOT of travelers like myself who have been using notebooks in this space for YEARS.

    Apple has given us yet another ~13x~9x~3lb notebook. The only difference is this one is THINK (useless) and has NO REMOVABLE BATTERY (big problem)

    I keep seeing Mac lunatics ranting about how the battery *IS* removable because you can surgically remove it. Its funny because thats pretty directly counter to the argument of "only special people use this type of notebook" since those "special people" are executives and road warriors who NEED TO SWAP BATTERIES WHILE ON A PLANE and also need to open the thing on a plane.

    Sorry to all the drooling Mac-o-philes, but the MBA is a miss.
    Reply
  • Griswold - Thursday, February 14, 2008 - link

    But but... its only 10 tiny screws of varying sizes that need to be removed to change the battery - anyone can do that on a plane!

    ;)
    Reply
  • Souka - Thursday, February 14, 2008 - link

    13.3" screen and 3lbs...

    Why not a
    faster laptop
    heckuv a lot more durable (proven)
    2.2lb (26% lighter!)
    upto 4GB of ram
    upto 200GB SATA HD, not old school PATA...
    Wi-fi a/b/g/n + EVDO broadband (Verizon or AT&T...you can choose!)
    you can CHOOSE what CPU, RAM, an HD you want....
    fingerprint reader
    hardware based security encryption (if you set it up and lose your laptop the data is %100 safe)
    choice of 4 or 8 cell battery....carry an extra and change without taking 10 screws out...or upgrade at any time
    can be purchasd in tablet-form...uber cool

    Oh yeah...prices start at hundreds less than Macair



    what am I talking about?? Lenovo X61...and other laptop makers are in the SUB 3lb market....


    True...Lenovo's development is way more experienced at ultra-portables than Apple... and I do say the Apple is "pretty" and sleek... but if I had a kid in college, I'd spend the $$ on a Lenovo laptop as I know it'll take the abuse much better than the Macbook air and heckuv lot less likely to be stolen...

    My $.02...

    Reply
  • OccamsAftershave - Thursday, February 14, 2008 - link

    And a X61 with a Penryn, 100GB HD and Ultrabase+DVD is $1600 vs. Air+DVD $1900.
    Only comparison negatives: with an 8 cell X61 is 3.3 lbs and resolution is XGA, not WXGA+.
    (And the 4 cell weighs 2.7 lbs. not 2.2 lbs.)
    Reply
  • lopri - Wednesday, February 13, 2008 - link

    quote:

    This wasn’t going to be my ultimate work machine, I wasn’t going to be running Photoshop on it, I just needed it to do some basic writing and web browsing. In many senses all I needed was a notebook-sized iPhone.

    What happened to the special, customized, and powerful Core 2 Duo CPU that Intel designed just for Apple?
    Reply

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