iPhone battery life in 2017: X is not on top

Apple firmware sometimes slows down older iPhones with aging batteries to keep them from shutting down unexpectedly. That's the recent news that has the tech world abuzz. But we're checking in on a totally separate, completely unrelated, iPhone battery story. Of the newest 2017 models -- the iPhone 8, 8 Plus and iPhone X -- which ones have the best battery life?

I've used every one of the new iPhones for weeks, as everyday phones on everyday commutes. We've done a lot of CNET battery benchmarks, too. And here's the spoiler alert: iPhone battery life could be better. And it underlines something I keep feeling about iPhones in general: their battery life is functional, but not notably fantastic.

Why are we returning to this issue now, rather than when the phones were released in September and November? Well, we had a few issues along the way. We use the included dongle to output audio and while playing a local video at half brightness. We then track how long that battery takes to die. All the current iPhones exhibited a lot of variance on our video playback battery drain test, so we reran the tests more often than usual over the course of several weeks, often interrupted by the myriad other needs we had for our several iPhone review samples.

The results, after repeated testing, are finally in. Out of this year's iPhones, the 8 Plus has the best battery life. The iPhone X, however, had the worst.

Times listed are the averages of several runs.

iPhone X: Battery life didn't impress

The X lasted an average of 11 hours, 38 minutes on our battery test. That's not great, and was considerably shorter than the 13 hours-plus average times that the iPhone 8 and 8 Plus managed. On the same test, the Samsung Galaxy Note 8 and OnePlus 5T ran for a little over 17 hours. In everyday use, however (meaning, our own anecdotal use), it seemed to fall more between the iPhone 8 and 8 Plus, which is closer to Apple's official estimates.

The iPhone X has a few new elements that could be leading to disappointing battery life in some instances. Its OLED display, which is brighter than the LCD screen on all other iPhones, could be a factor; OLEDs, despite what you'd think, can drain power when they're not running darker backgrounds.

Another possible factor: The TrueDepth front camera and its infrared Face ID sensor could cause drain if used repeatedly. Our phone tests are conducted on a bench in our PC lab with the phones pointing laying flat. It's unlikely that TrueDepth is affecting our test in any way, though, since we're playing back video and the phone lock screen isn't being engaged.

In my everyday use over several weeks, I've often had to recharge the X by midday to be safe. It's a step below the Plus phones I've used, and even with Apple's iPhone 7 Plus and 8 Plus, I didn't feel completely battery-satisfied.

The best for battery: The iPhone 8 Plus

The 8 Plus remains a consideration for anyone who wants a tiny bit more battery oomph. But, even then, we didn't get results that were better than leading Android phones.

But the 8 and 8 Plus are closer than you'd think. Take a look at our results: the iPhone 8 lasted an average of 13 hours, 31 minutes, while the 8 Plus lasted an average of 13 hours, 44 minutes.

2016 vs. 2017 iPhone battery life: Similar expectations

Perhaps the biggest news with our battery tests is that -- it's not much news at all. While iPhones post huge gains in speed and performance year over year, their battery life tends to be largely unchanged. In fact, the 2017 iPhones (8 Plus and 8) actually have smaller batteries than their 2016 counterparts (7 Plus and 7), albeit with the exact same battery life expectations (per Apple) because of the newer models' more efficient chips.

Indeed, Apple never claimed marathon battery life for the iPhone X, either. Its published battery specifications are equal to that of the iPhone 8 on internet use (12 hours) and wireless video playback (13 hours), while the 8 Plus is rated for an hour more on each task. Meanwhile, the X and 8 Plus rank considerably higher than the 8 on talk time and wireless audio playback (21 and 60 hours on the larger iPhones versus 14 and 40 on the iPhone 8, respectively).

Charging speed requires expensive extras

Charging any of the new iPhones with the included 5-watt plugs isn't fast, either. Apple supports quick charging on all the new iPhones, provided you buy USB-C charge bricks sold separately, and then also buy Lightning-to-USB-C cables. The least expensive option is simply getting a 12-watt AC adapter, normally intended for iPads, that will at least help out.

Charging via wireless Qi-compatible contactless accessories is potentially faster now that iOS 11 supports 7.5-watt chargers, but even then, it still wouldn't feel fast charging. This matters because, if I'm charging the phone mid-day, I'd like the process to be faster with the included cable and plug.

Additional testing

Note that tests by Tom's Guide and the Wall Street Journal found the X battery landed squarely in between the 8 and and the Plus. We're continuing to test battery life on these iPhones as part of a longer analysis of wireless charging and will update our scores if we see notable changes.

Similarly, as a growing number of Android phones in 2017 continue to ace our battery test, CNET is looking to update the test as we move into 2018. We'll be sharing more info soon, but the long story short is this: we'll likely be moving the goal posts to measure up to the expectations of newer, more efficient chips like the Snapdragon 845 and (presumed) Apple A12.

I'd still like the iPhone battery to be better

Maybe next year, Apple will make a leap forward in iPhone battery life. It didn't happen in 2017. Instead, we got a lot of other great things: big leaps in speed, and in the case of the X, an improved design and groundbreaking Face ID system.

This year's iPhones are great -- but I'd love to stop worrying about my battery life.

• iPhone 8: Read the updated review
  
• iPhone 8 Plus: Read the updated review
  
• iPhone X: Read the updated review