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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  • bsozak - Monday, January 18, 2010 - link

    For the price difference between the two it seems hard for me to justify the SSD version, though intuitively it would seem like the advantages would be greater. The odd thing to me is the number of people who claim to really notice the difference, even though the benchmarks don't seem to be that drastically different in a lot of areas.

    I also wonder if the type of SSD makes a difference? I've heard great things about Runcore SSD which has some really good pricing here - but if I end up dropping that kind of coin for moderately better performance, I don't think I'd be too happy.
    Reply
  • bsozak - Monday, January 18, 2010 - link

    That link didn't seem to take, so let's just try this: http://bit.ly/6Yz3cU">http://bit.ly/6Yz3cU Reply
  • steveyballmer - Tuesday, July 08, 2008 - link

    It is amazing to me that so many people can't seem to see through the Steve Jobs Reality Distortion Field! Everytime he gets up at one of his sissy-boy "conventions" he performs cheap magic tricks for the faithful, sometimes he even drags well meaning journalist along with him!
    The platter he is serving on in this picture is a "Macbook" (even though it's thinner than a magazine) Hot Air.
    Think about it, you are getting less for more! Skinny for plenty! Scrawney for money! Slim for uh, um, I can't think of a rhyme but if I could it would be something bad.
    PEOPLE, PEOPLE, PEOPLE!
    Big is better! They have the iPhone, we have a CoffeeTable!

    C'mon!
    http://fakesteveballmer.blogspot.com">http://fakesteveballmer.blogspot.com
    Reply
  • pink78 - Friday, April 11, 2008 - link

    I've heared that next-gen MacBook pros are to recieve the multitouch trackpad: http://www.maconair.com/next-gen_macbook_pros_to_g...">http://www.maconair.com/next-gen_macbook_pros_to_g...

    is that true?

    Reply
  • RedWolf - Thursday, February 21, 2008 - link

    The start of the review comes off as a bit too pro-apple. It was quite thorough and by the end, I didn't feel the same pro-apple bias. I thought the comparison to the Ferrari was excellent. The MBA is a luxury. If you can't afford two laptops you should get a more practical laptop and skip the MBA.

    I was dissappointed in the lack of a mention of Windows on the MBA. My Dell Inspiron 700M is getting a bit old and I'm looking for a replacement. I have a need to run windows regularly. How does the MBA run windows in bootcamp? Does the drive sharing work?

    I can see the MBA working for people who have the money to spend on a third computer (second laptop) and for anyone who does a lot of typing but needs a laptop that can be carried around. I can also see it working for my wife (the primary user of our 700M). She wants something that is light and easy to carry around the house. One of my biggest complaints about my 700M is the cramped keyboard. A full size keyboard would be wonderful.
    Reply
  • AnnonymousCoward - Tuesday, February 19, 2008 - link

    1 button trackpad? Lame! Reply
  • kac77 - Tuesday, February 19, 2008 - link

    I feel the review was good overall. But really I think the MBA was put in the most positive light as possible. Everyone says it's a niche product, well what niche is that?? Once you start to go deeper the whole niche theory, or "Its not made for you" aspect starts to appear rather light in common sense. Lets look at the supposed markets:

    College Students

    OK the MBA could possibly work it here. However, how many of you had two computers when at college? The MBA really does require a companion PC in order to assure the buyer that he/her can reinstall the OS if problems arise. In addition, having 1 USB port in college would be insane. When I was in College mine got a thorough work out. I transferred files to and from via USB drives, logging onto the network, installing software which was apart of the class. That one USB would be a hindrance no matter how you look at it.


    Traveling Managers (Marketing or Sales I presume)

    These people use their laptops even more than college people do. They are designing presentations. Most of them require the need to VPN into their office network in order to retrieve misc files they might require. They are downloading email often from remote locations so having 3G capability would be mandatory. Since there isn't a express port or PCMIA slot they are stuck with WIFI?? Trust me on this the sales guy isn't sitting in Starbucks in order to download his/her email or work on the latest spreadsheet.

    These points are what I'm talking about. When you just scratch the surface it appears fine but when you go deeper the lack of ports, no drive, no 3G, no Ethernet, (and no, being in IT I am not going to have the Marketing department change their own battery or hard drive) I think it makes the MBA become more of a product you get to do small work on a weekend when you happen to want a latte.

    Finally what wasn’t touched on at all, transferring files from the host PC. Most likely you are going to want to put some music on your computer, or just sync those files that you need for work. I’ve heard reviews from other sites that this process can take way more than 2.5 hours more like 5 or more. Some weren’t even able to complete the process without using the Ethernet dongle. In addition, you can’t use the one USB port with the Migration Assistant. Just how much weight would have been added to put on FireWire anyway???

    The overall thing with this device is that in order to achieve a baseline of functionality you are conceivably carrying around an Ethernet dongle, possibly the Super Drive (probably not in college, but most definitely if you are traveling) a USB extension cord, plus some sort of 3G device if you really want to be mobile. Once you are carrying around all of these things have you really saved any weight? With 3G this product really would have made some sense. The argument to looking forward where all information is on a network somewhere or at home would have held some weight. Without it the product comes off as trying to sell a drowning man a glass of water.

    This device really has one market …the CEO. This is a person who checks email at home or in the office isn’t really going to be accessing the VPN much from a remote location. Having 1 USB port would be fine. He isn’t doing the presentations, someone else usually is. At best while on the go he’s taking notes. For this person this device makes perfect sense but for anyone else I just don’t see it.
    Reply
  • MacTheSpoon - Saturday, February 16, 2008 - link

    Thanks very much, this was a really comprehensive, excellent review! Reply
  • Phrozt - Friday, February 15, 2008 - link

    Two comments about the benchmarks, one question about the battery.

    First, about the battery. It's been said that one of the shortcomings of the iPhone is that there are a limited number of times the battery can be charged. Does the Air suffer this same fate? Obviously this would have less of an impact than the iPhone situation, because the battery can clearly be removed and therefore replaced, but I'm still wondering about it's limits (especially after the mention of the 8 hour bug).

    As for the benchmarks, I think something needs to be said about the differences of expectations in real world use (in regards to the SSD vs. stock HDD argument). You said that you noticed everything starting/working quicker w/the SSD, but the benchmarks showed that in write situations, it showed an obvious disadvantage. I think it's important that you stress real world expectations in this situation. The more you use a computer, the more your expectations change. You *want* a program to start up at the snap of your fingers, but you *expect* saves/exports/transfers to take a long time. Therefore, from a real world useability standpoint, the SSD would be much better experience, because it improves in the areas where you have high expectations, and only falters in areas that you already have low expectations.

    Finally, about the usage tests. All three of these tests are heavily read reliant with almost no writing. Since the SSD takes longer to complete write projects, and therefore more energy overall to complete the process, I would be interested to see what the usage time would be if you were to script out a process that included a lot of PDF/image/file conversions/saves.

    All in all, a very good, in-depth and objective review. Wonderful job.
    Reply
  • totenkopf - Friday, February 15, 2008 - link

    "Thinner and lighter" only covers about two thirds of ultraportable, It's still basically the same footprint... how is that helpful? Can you not handle two extra pounds and the oppressive thickness of the mac book? When you open it up it's the same size as the rest of the mac books! If you take an old walkie-talkie cellphone and make it lighter and slimmer and than call it ultra portable... IT STILL DOESN'T FIT IN YOUR POCKET! , They completely missed the point of the ultra portable! The asus eee can operate as an extension of your desktop by allowing you to write, surf and accomplish minor tasks away from your primary machine. Yes, it is not the most comfortable on the eyes or the hands... It's not supposed to be! Apple was afraid to make the necessary sacrifices to make a true ultra portable computer.

    As a thin laptop it's a failure! No removable battery? What if i want to use some optical media on a train/bus/plane? I have to plug in some stupid portable optical drive? that isn't convenience that's a tragedy. I don't care how nice the display looks if i'm looking at a machine with worse specs than a $700 cheaper mac book. Once again, Apple is selling form over function... that's right, you get nothing extra for your money, just the envy of other iNerds.

    And to the author: describing it as a ferrari is laughable. True, it isn't fit for use as your primary machine, but isn't it supposed to perform better than your primary machine? I'd call it the mac book "airhead". It's like that blonde, oxygen thief piece of arm candy you always wanted to make you look good around your friends!It doesn't actually do anything very well, but at least it's inadequate for everyday use.
    Reply

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