Battery Life

Battery life is something that has changed drastically in just the last several years. Improvements to all parts of the typical laptop have contributed to some fairly massive increases in battery life. With the XPS 13, we have a unique opportunity. Not only is this our first Broadwell-U based notebook to be reviewed, but this is also the first chance we have had where we can test two virtually identical computers, but with different resolution displays.

We have known for some time that higher resolution, and especially higher pixel density displays, can have a significant impact on battery life, but with these two laptops configured virtually identically except for the display, we can get a good look at the trade-offs between a super crisp display, and one that perhaps does not have quite the visual fidelity, but could perhaps increase the usable time away from the power outlet. Dell is claiming that the FHD (1920x1080) version of the XPS 13 can get over 15 hours of battery life, and the QHD+ (3200x1800) version is capable of over 11 hours. Those are lofty goals, and ones we will put to the test.

To test battery life, we have our usual two tests. The first is our Light test, which cycles webpages until the laptop turns off. The Heavy test increases the number of pages loaded, adds in 1080p movie playback, and an 8Mbps file transfer. All of our battery tests are conducted with the display set to 200 nits brightness (or as close as possible) and the laptop is set to Power Saving mode to give it the best chance at the test. I also checked the display brightness several times during the run-down to ensure that the display was not dimming over time.

Battery Life 2013 - Light

Amazingly, Dell claims 15 hours 21 minutes of battery life, and on our Light test we hit exactly that. The QHD+ model clocked in at just under 10 hours, which is in itself an amazing result. Our previous record holder for this test was the 13-inch MacBook Air, which has a 54 Wh battery versus the 52 Wh in the Dell. So even with a smaller battery, and a display with over four times as many pixels, the Dell XPS 13 has basically tied that result under Windows. The MacBook Air under OS X is still ahead.

Perhaps more impressive, the FHD model, which still has 1.6X as many pixels as the MacBook Air, achieves 60% more battery life. It is a pretty amazing result. Dell has obviously worked hard on power consumption for this model. Intel’s new CPU would certainly be part of this, but on our light test, the CPU is not as big of a factor as the display. With the IGZO TFT, the benefit is certainly quite impressive. It will be interesting to see if other manufacturers are able to come anywhere near the results of the XPS 13 over the coming year.

Dell's product page, outlining battery life estimates

What is amazing is that Dell was able to deliver near the top of the charts in battery life with the high DPI version as well. The Yoga 2 Pro has the same size display and the same resolution, and a similar battery capacity as well, yet it scores 154 minutes (2.5 hours) less. High DPI certainly has a big hit on battery life, but with the XPS 13, it still lasts almost ten hours on our light test.

However, I do have to note that the battery life was measured with Dell’s adaptive brightness enabled (since it could not be disabled). In my testing, the brightness would only really change on large contrast swings. It would deviate only a few points up and down most of the time, and I did check the brightness a couple of times during the battery life tests to ensure it was still at 200 nits. Still, there is certainly a potential for minor variations due to the adaptive brightness.

UPDATE: I have worked a way to get around the Content Adaptive Backlight Control for the battery life testing, and was able to achieve 15 hours of battery life on the light test in balanced power as requested by some of our readers. I am very confident in this result and tested the brightness levels for several hours without having any variation. Unfortunately it still cannot be disabled outright, so the display still can not be calibrated.

Battery Life 2013 - Heavy

Moving on to your Heavy test, the QHD+ model is once again neck and neck with the MacBook Air, but the FHD version jumps well out in front of the next closest contender, the Atom based HP Stream 11. Eight hours for our Heavy test is truly impressive battery life. The CPU isn't maxed out, but with video playback, internet surfing, and a constant WiFi load most other laptops falter. The XPS 13 is still delivering "all day" battery life on the FHD model.

Next up, we will take a look at the Normalized graphs, which remove the battery size from the equation so that we can get a feel for the overall platform efficiency.

Battery Life 2013 - Light NormalizedBattery Life 2013 - Heavy Normalized

The FHD model once again tops the charts on light use, and by a large margin. On the Heavy normalized graph, the XPS 13 nearly matches the 5 watt Atom based HP Stream 11, which has half of the pixels to drive. It is a very impressive result. In the event that you need even more battery life, Dell also sells an optional 12,000 mAh battery that connects to the charging port, and this will almost double the battery life.

Dell Power Companion

Dell's Power Companion accessory is a 12,000 mAh (otherwise known as a 12 Ah) battery, which comes with a couple of connectors to hook up to the various Dell power inputs on their laptops. To charge it, you plug the laptop power adapter into the Power Companion. This may seem like a bad idea, since your laptop charging cable would be indisposed, but you can simply put the Power Companion in the middle, so the adapter charges the Power Companion, which then charges the laptop.

The nice part about the Dell Power Companion is that you can easily charge the laptop while it is in your bag during travels. It will also charge any other USB devices, and it comes with the necessary adapters to hook to any Dell.

Charge Time

With just a 45 watt power adapter, one might be worried about the charge times on the XPS 13. However they seem very reasonable. The FHD model was able to charge the battery in just over two hours. The QHD+ model required three hours, but a significant amount of time was spent at 99% charge, as you can see in the graph below. Also note that if the laptop isn't in use, charge time should go down a bit.

Battery Charge Time


Dell has outfitted the XPS 13 with stereo speakers located on the sides of the laptop. They rate the internal amplifier at 1 watt per channel, and Dell states that they are tuned with Waves MaxxAudio Pro. Let’s take a look at the frequency response. All readings were done with the sound meter one inch above the trackpad.

The frequency response is pretty good for such small speakers, and the volume is quite loud as well. Listening to music, the XPS 13 could hit around 86 dB. Sound quality was decent as well with good response in the low range. I was a bit surprised with the speakers' abilities considering how inconspicuous they are on the sides of the device, so Dell has done a nice job engineering them. Putting them on the sides is also a nice compromise between having them on the top (where there is not much room due to the width of this laptop) and having them underneath, where they tend to be on a lot of devices now. There is a good sense of stereo, and the sound is not muffled by whatever surface the laptop is resting on.


Broadwell-U is a 15 watt CPU and therefore it requires a fan. For many scenarios the fan is not required at all, but if the CPU is working the fan will come on at around 43 dB, and ramp up to a maximum of 47.2 dB. Overall, the noise was quite easy to live with. This is at a distance of 1", so from a normal user position the noise is far less noticeable. The pitch of the fan was low enough that it would not irritate like a smaller, higher rpm fan would.

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  • trane - Thursday, February 19, 2015 - link

    This must deserve an Editor's Choice award?

    The only major drawback is the auto-brightness, which I'm sure will be fixed with an update soon. IINM, the original Acer S7 had a similar issue which they fixed with a firmware update. Once that is fixed, I don't think there's any real con! Yes, we would all love it to do Yoga style acrobatics, and have touch for $800, but let's be realistic. Even with the battery life hit the QHD+ option is still class leading! Dell can't fight the the current state of technology...

    But the fact that these are brought up as shortcomings just tell us how great this laptop is. I mean, no one's complaining that the $1000 Macbook Air sports an archaic non-touch non-matte low-res TN panel.

    Some other sites seem to be reporting much lower battery life versus Macbook Air. I wonder if that is because they are penalising the display for being brighter? Or using Chrome? Chrome has godawful efficiency right now with Hi DPI support, I'm surprised that this is not more commonly known! My laptop does 8 hours with IE, 5 with Chrome.
  • RT81 - Thursday, February 19, 2015 - link

    Believe me, PLENTY of people are complaining about the screen on the current Macbook Air. Nobody cares about touch on a Mac, but they certainly care about the TN and low-res part.
  • repoman27 - Thursday, February 19, 2015 - link

    "The FHD model (1920x1080) arrived with a single 4GB memory module and the QHD+ version came with 2x4GB, which gives us the chance to check the performance differences between the single-channel memory and dual-channel memory."

    These machines are memory down (soldered RAM) configurations. There are no modules, and Lenovo would be insane to not keep both channels populated and simply use different density packages for the different models. Are you sure they're shipping single channel setups?
  • repoman27 - Thursday, February 19, 2015 - link

    D'oh! Dell, not Lenovo.
  • Brett Howse - Thursday, February 19, 2015 - link

    Sorry I made a mistake there. It is in fact 2x2GB and the article has been updated.
  • Hulk - Thursday, February 19, 2015 - link

    Is it possible that Dell sent the laptops without the ability to change auto brightness on purpose so that the battery life tests would be extraordinarily high? I'm sure they'll be good when the update to turn auto brightness off arrives but most people will remember the hype of the original amazing battery life tests. With all due respect to Anandtech I think they should not have posted battery life tests until they auto brightness can be turned off. It's not really an apples-to-apples (no pun intended) comparison.
  • trane - Thursday, February 19, 2015 - link

    To be fair, he did check the brightness from time to time. If there were any notable changes I'm sure they would have withheld the results.
  • Hulk - Thursday, February 19, 2015 - link

    You are right and I'm not in ANY way implying there was an bias on Anandtech's part. It's a tough call. Publish the battery life to get the results out there quickly for readers with the caveat of not being able to disable auto brightness or just write "the battery life results look to be very impressive but we are not going to publish them until we can disable auto brightness." I'm just saying I would have gone with the 2nd option for two reasons. First, if with auto brightness off the results are dramatically lower than Dell pulled one over. And second, to send a message to manufacturers that if they don't allow fair comparisons due to locked software not all testing results will be published.

    As I wrote above it's a tough call and I respect Anandtech's decision I just disagree with it.
  • andrewaggb - Thursday, February 19, 2015 - link

    The battery results are fantastic, I wonder how much the auto-brightness plays into it. I wonder if you pointed a bright light at the light sensor if that would force the brightness to stay at maximum.
  • JarredWalton - Thursday, February 19, 2015 - link

    FWIW, I've run tests with laptops at 100 nits before just to see how much that would help. The difference between 100 and 200 nits is usually on the order of 30-60 minutes at most, and often less. However, to get 15 hours from a 42Wh battery means that the laptop is using around 2.74W in our Light workload. If the display adaptive brightness saves 1W, battery life would drop to 11.24 hours (give or take). Which is what happens with the QHD+ panel I should note, though how much of that is the display alone and how much is caused by a higher load on RAM and CPU/GPU to handle the higher resolution is difficult to say.

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