Does a Dark Watch Face Save Battery Power on Apple Watch?
Why Do Dark Themes Use Less Power?
Apple opted for OLED display technology for the Apple Watch from the very first model. Unlike traditional LED-lit LCD screens, OLED is a self-emissive technology. That means there’s no need for a backlight at all because each pixel generates its own light.
This enables for pixel-level light control and perfect blacks. To display pure black, pixels are simply turned off. This consumes no power and makes the rest of the watch face stand out against the deep black background.
Apple
Watch faces that use mostly dark or black elements use less power than a watch face with lots of bright white or colorful elements. The brighter a pixel, the more power it consumes. If you can replace a bright solid-colored background with a black one, the display will use less power because more pixels are in the “off” state.