Since iOS 13 was released a few weeks ago, there have been rumblings that switching to Dark Mode could potentially extend your iPhone’s battery life. It was never proven and Apple itself refrained from marketing Dark Mode as something that could help with battery life, but a recent experiment seems to have proven just that.

The prolific YouTube channel PhoneBuff just released a video showing two robotic arms interacting with two identical iPhone XS Max’s, one with Dark Mode turned off and one with it turned on. After a day of testing, the iPhone that wasn’t using Dark Mode was dead while the iPhone using Dark Mode still had a 30-percent battery.

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The results will no doubt vary depending on the brightness of the screen as well as the types of apps you’re using, and Dark Mode will have a much more significant impact on iPhones that have OLED displays — the latest iPhone 11 Pro (Max), last year’s iPhone XS (Max) and the two-year-old iPhone X. OLED displays have much better contrast because they’re able to completely turn off areas that are meant to be black.

There’s a good chance that iPhones with LCD displays, meaning the iPhone 11, iPhone XR, iPhone 8 (Plus) and iPhone 7 (Plus), won’t get quite the same battery-saving benefits of Dark Mode. LCD technology simply isn’t as efficient.

If you have an iPhone running iOS 13 and you don’t know how to switch to Dark Mode, click the link below.