Battery Life & WiFi Performance

Last but certainly not least in our look at the MacBook is a look at its battery life and WiFi performance.

Along with the technical considerations that have gone into making the MacBook as small as it is, I would consider the subject of battery life to be the second most interesting aspect of the MacBook’s design. For on the one hand, the CPU at the heart of this laptop is Core M, a very low power CPU specifically designed for thin & light devices, which on its own doesn’t draw all that much power. On the other hand in constructing the MacBook Apple has ditched the MacBook Air’s standard DPI TN panels for high DPI Retina IPS panels. As we’ve seen in other Apple products in the past, going Retina incurs a significant power cost, as the high DPI displays require a much stronger, much more power hungry backlight to light up the display. Apple needs only to pay this cost once, but it’s an expensive cost.

All the while Apple also has to deal with the battery capacity limits of such a small chassis. Using terraced batteries has allowed Apple to maximize the amount of volume the MacBook’s batteries occupy, however at 39.7Wh this only gets them up to roughly where the 11” MBA (38Wh) already sat. The end result is that relative to the 11” MacBook Air Apple has virtually the same battery capacity to drive a less power-hungry CPU and logic board paired with a more power-hungry display.

Officially the MacBook should be able to hit 9 hours of runtime on a light web workload, and 10 hours with video playback. This happens to be identical to what the 11” MacBook Air is rated for, and in practice would be very close to what the Haswell-based 11” Airs hit as well.

Meanwhile to test battery life, we have two workloads. Our light test is light web browsing, and our heavy test increases the number of pages loaded, adds a 1 MB/s file download, and has a movie playing. We set all displays to 200 nits.

Light Workload Battery Life

In practice what we find is that by our testing methodologies the MacBook falls about an hour short, clocking in at 8 hours and 5 minutes. The difference in battery life most likely comes down to differences in how we test; Apple bases their estimates on 75% display brightness, whereas we test at 200 nits, which in the case of the MacBook is around 85% brightness. If we turned our brightness down to 75% I suspect our results would come very close to Apple’s, at the cost of dropping below 200 nits of brightness.

Even by our own testing standards, the MacBook’s battery life is enough to get the laptop through an entire work day (8 hours) – if only just – so while we can’t hit 9 hours at our preferred brightness Apple isn’t in too poor of a position for such a small laptop. In practice what this means is that the MacBook does just a bit worse than the 11” MacBook Air, essentially falling behind by 40 minutes of runtime. However given the fact that the MacBook is also physically smaller than the 11” Air, this is not an unexpected tradeoff.

Putting things in a bit larger perspective, thanks to Intel’s massive energy efficiency gains from Haswell in 2013, the MacBook looks very good compared to the older 2011/2012 11” MacBook Air models. From a battery life perspective the new MacBook easily exceeds those models, is physically smaller than those models, and all the while delivers performance that at worst is equivalent and at best better than those models. Put another way, Apple has been able to hold performance constant while bringing down both the size and greatly improving the battery life.

However if you want better than 8 hours on a light workload, then even the MacBook is no substitute for a larger laptop with a bigger battery. There’s only so much that can be done on 39.7Wh, and as a result the 13” MacBook Air will remain unmatched as Apple’s long-haul Ultrabook.

Heavy Workload Battery Life

Meanwhile with a heavy workload the MacBook’s fortunes improve. No longer just in the middle of the pack, at 5 hours and change it’s offering runtimes close behind the 13” MacBook Airs. This shift in relative performance is not unexpected, and is closely tied to the balance between CPU power consumption and display power consumption. Compared to the light workload, the heavy workload requires that the CPU draw quite a bit more power all the while the amount of power drawn by the display is virtually unchanged. As a result the higher powered MacBook Airs see a big step up in their power requirements, while the Core M equipped MacBook sees a smaller step up.

Heavy Workload Battery Life (As a Percentage Of Light)

In fact if you look at heavy workload runtime as a percentage of light workload runtime, the 2015 MacBook has the smallest drop in runtime out of all of the MacBooks. Apple’s latest laptop gets 62.2% of its light runtime under the heavy workload, compared to 50.1% for the best MacBook Air. The only thing with a similarly small decrease are the Retina MacBook Pros, whose large, Retina displays result in a similar situation.

Somewhat paradoxically then, the MacBook looks best under a heavy workload, even though its processor is relatively slow. Ultimately this is more an intellectual curiosity than anything else, but it’s a great example of how the MacBook’s component selection has resulted in a much different power consumption balance between the display and CPU than what we’ve seen on the MacBook Airs and similar Ultrabooks. If the display isn’t the single biggest power draw on the MacBook, it’s certainly going to be a close second.

WiFi Performance

Our final benchmark is a quick glance at WiFi performance. The MacBook ships with a Broadcom 2x2:2 802.11ac solution, which means that in theory it is capable of delivering up to 833Mbps.

For our WiFi benchmark we copy a large file from a Gigabit Ethernet connected SMB file server, timing how long it takes to transfer the complete file and calculating the average. All laptops are placed within a few feet of the router to maximize their achievable bandwidth and minimize interference. For the MacBook we’ve gone ahead and run this test under both Windows and OS X, to showcase any performance differences between the two OSes.

WiFi Performance - TCP

Under Windows the MacBook hits 389Mbps, about 47% of its theoretical maximum performance. Compared to other Windows laptops this is a mixed bag, with some laptops able to hit as high as 500Mbps, and others coming up much shorter. In the case of the MacBook I suspect the all-aluminum chassis is not doing it any favors. Meanwhile performance under OS X is a bit worse at 333.7Mbps, most likely due to OS X’s less extensively optimized SMB support.

While I imagine it’s impractical from a design perspective, given the fact that the MacBook only has a single USB port, I would have liked to see a 3x3:3 solution for the MacBook to allow it to achieve better WiFi performance. Even 3x3 solutions seldom keep up with GigE in the real world, but the MacBook certainly has the SSD and processing power to handle faster speeds than what we’re seeing here.

Windows Performance Final Words


View All Comments

  • BittenRottenApple - Wednesday, April 15, 2015 - link

    Edit, please forgive the double post, thank you very much. Reply
  • sbuk - Thursday, April 23, 2015 - link

    No. Not with rampant idiocy like yours. Reply
  • ppi - Wednesday, April 15, 2015 - link

    While I am no lover of Apple (in fact, Apple products can't cross my door), you need to give credit where its due.

    1) That single port can serve (yes with dongle, but still) as single cable to plug you to power, ethernet, external display, keyboard and mouse. Now this is mucho better than my current Lenovo T-series, where I need to plug all those cables individually every time I change location.

    2) 8 GB RAM and 256 GB SSD is insufficient? You came here back in time from 2045 or what? Show me notebook with better BASE specification.

    3) If you are processing spreadsheets, that Core-M cannot handle, it must be quite a chore to do it on standard notebook as well. I would suggest optimizing the spreadsheet (less dynamic formulas where it is not necessary) or if it does not help, considering moving your work to SQL server.
  • smorebuds - Tuesday, April 14, 2015 - link

    Name one Core M device that's in the netbook price range. The UX305 is probably the cheapest decent Core M laptop and it's $699 base price with 8gb ram and 256gb ssd. How does that equate to a netbook exactly?

    The logical successor to netbooks are the sub-$300 Windows/Chromebook Atom laptops. While they are certainly snappier than the old Atom netbooks, they are also unmistakably budget devices.

    I have an HP Stream 13 and an UX305, and while I appreciate the $200 Stream for what it can do, it's nowhere near as responsive as the UX305 - aka NOT A NETBOOK.
  • smorebuds - Tuesday, April 14, 2015 - link

    Ok do you consider every small laptop to be a netbook? I guess I assumed we were taking performance into account as well... Reply
  • MykeM - Tuesday, April 14, 2015 - link

    Is a netbook equipped with a SSD that read/write in the 800/400 MB/s range? Not even the Dell XPS13 comes with such SSD. Reply
  • bobhays - Wednesday, April 15, 2015 - link

    These arguments are so ignorant that I had to create an account so I could reply. The new MacBook IS a netbook. A netbook is a small, portable laptop that has enough processing power to do basic office tasks and browse the internet. EXACTLY what this laptop is designed for. A netbook is not defined by it's price range or quality, it is defined by it's purpose. If someone made a cheap, but exteremely well performing sports coupe, you are not going to say no that is not a sports car because it doesn't have the same quality as a ferrari. Just because the new MacBook is more expensive and has better specs (not necessarily performance) does not mean it serves another purpose. It does the same thing as a netbook (because it is one) for a different market. The only reason people are arguing right now over whether this is a netbook or not is because there were no premium netbooks before so everyone assumed a netbook means weak computers that lag behind. A netbook is essentially a low performance (and previously low priced) ultrabook and that is the perfect description for the new MacBook. Thanks for reading and if you disagree please make a point and not an ad hominem. Reply
  • zhenya00 - Wednesday, April 15, 2015 - link

    I think you blur the lines too much. A netbook is exactly as its name implies - a device primarily designed to browse the Internet. The netbook has always been defined by a gimped operating system and/or (nearly always and) cheap construction in order to make it as affordable as possible.

    The MacBook is not a netbook.

    - It has a full operating system, exactly the same as every other Mac computer.
    - It has premium parts befitting the most expensive laptops on the market.

    The ONLY thing you seem to be focusing on is the processor - there is nothing else in the MacBook design that could even remotely say 'netbook.' Is the 11" MBA a netbook? It's smaller and cheaper? Is a 2010 MBP a netbook? Because it has a slower processor than this MacBook.

    The new MacBook is a laptop built on the premise that much modern computing does not need cutting edge CPU power, and can instead be built to prioritize things like battery life, silence, device size and weight. That doesn't make it a netbook.
  • BomC - Saturday, February 06, 2016 - link

    Because of market saturation but also in acknowledgment of a widely diverse market, the industry is moving steadily away from default one-for-all solutions towards a far more diversified picture. In that sense, you might see this Macbook as an equivalent of the Galaxy View 18" tablet: purposely niche-oriented, experimental products in search of markets sectors for which they are suited. This is true for software as well. As a writer, I had to make do with a MS-Word-alike application for years; everyone's word processor was essentially the same Swiss army knife of an app. Nowadays I can use iA Write for distraction-free, concentrated writing, Mellel for academic pieces, Scrivener for writing setups and a whole host of apps for screenwriting. Can't speak for other people but I've never had it so good. Reply
  • Onionart - Wednesday, April 15, 2015 - link

    Lenovo Yoga 3 Pro is also using Core M processor and as is many other ultrabooks in the market. This is the trend. Netbook is a name created for calling a specific class of computers. It is like calling all printers and scanners as xerox machines..... Reply

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