Do black wallpapers save battery on an OLED iPhone?
Yes, a little. How little depends on your brightness and on how much of the screen the wallpaper actually covers.
Why black costs less on OLED
An OLED pixel makes its own light, so its power use grows with how bright it is. A pixel set to pure black, #000000, is switched off and draws almost nothing. On an LCD the backlight stays on whatever the picture, so a black wallpaper saves nothing there. Every iPhone since the X uses OLED except the XR, the 11 and the SE models.
Why the saving is modest
The wallpaper is only visible on the lock screen and between your icons on the home screen. Most of the time the screen shows apps, which have their own colours. Studies of dark mode, which turns whole apps dark, found large savings only at full brightness and single-digit percentages at the brightness people usually use. A wallpaper, which covers much less of your day, saves less than that.
Where it does help
- The always-on display of Pro models shows a dimmed wallpaper for hours. A mostly black wallpaper means most of those pixels are off.
- High brightness outdoors, where every lit pixel costs more.
- Pure black, not dark grey. #0a0a0a is still a lit pixel. The wallpapers in Dark & OLED are built on #000000 for that reason.
The better reason to choose one is how it looks: on OLED, a single line of light on true black seems to float, and the edge of the screen disappears into the frame.