Comment: Why the iPhone X appears to be power-hungry despite more efficient OLED screen

We noted earlier a Chinese regulatory filing that appears to confirm an earlier report that the iPhone X will come equipped with 3GB RAM. That same filing also contains another interesting number: the apparent battery capacity.

Serial leaker Steve Hemmerstoffer tweeted the image showing a battery capacity of 2716mAh – even higher than the 2691mAh battery found in the iPhone 8 Plus, with its far less power-efficient LCD screen …

LCD screens use a backlight to light up the entire display area. Even an area of the screen that is solid black gets the same amount of light, it is simply blocked by the black LCD pixels. OLED, in contrast, lights individual pixels, without any backlight required. A black area of the screen therefore uses no power.

It’s difficult to find true like-for-like comparisons, as manufacturers typically take advantage of the power efficiency of OLED by making their displays brighter. But a little Googling suggests that an OLED screen ought to use around two-thirds the power of an equivalent LCD one.

The iPhone X does, of course, have a somewhat larger display than the iPhone 8 Plus, at 5.8 inches rather than 5.5 inches, but 5% more display area is relatively trivial compared to the power savings of OLED.

This suggests, then, that there’s other technology in the iPhone which requires significantly more power than less advanced models.

One obvious candidate is the optical image stabilization system. While the iPhone 8 and iPhone 8 Plus have OIS on one camera, the iPhone X has it on both cameras. OIS has motors electromagnets that physically move the lens to counteract hand movements, and this requires significant amounts of power.

A second likely suspect is the TrueDepth camera system. This is used not just for face recognition for unlocking the phone and authorizing Apple Pay transactions, but also for the new Animoji feature and the Portrait Mode when used with the front-facing camera.

The TrueDepth camera requires an infrared ‘flood illuminator.’ Although it doesn’t use visible light, this will use power levels not massively dissimilar to a visible-light flash, but will be operating for much longer periods.

So even with a larger battery and much more power-efficient display, Apple clearly finds that the extra features on the iPhone X eat significant amounts of power. It cites 12 hours of Internet use and 13 hours of video playback against an hour more of each for the iPhone 8 Plus.

When it comes to recharging your iPhone X or iPhone 8 battery, you’ll have the choice of fast-charging via wire or wireless charging with a pad, wireless charging without a pad or using furniture. Manufacturers of Qi chargers have wasted no time in adding iPhone compatibility to their product descriptions.

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iPhone 8

The direct upgrade to the iPhone 7, featuring a glass back, wireless charging, faster processors, and an improved 12MP camera.

iPhone X

Apple's bezel-less, premium 10th anniversary smartphone.

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Ben Lovejoy

Ben Lovejoy is a British technology writer and EU Editor for 9to5Mac. He’s known for his op-eds and diary pieces, exploring his experience of Apple products over time, for a more rounded review. He also writes fiction, with two technothriller novels, a couple of SF shorts and a rom-com!

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