Does dark mode save battery? It depends on the type of screen: here's all you need to know
Now that dark mode has spread a bit everywhere, thanks also to the official support by Android 10 and iOS 13, many users with OLED screens are starting to experience the benefits of dark mode.
Benefits especially for the battery and autonomy: thanks to the night mode, in fact, smartphones and tablets consume less power and the battery lasts much longer. But how much longer? It depends mainly on the type of screen: on old LCDs the difference is not so marked, while on LED displays (whether PLED, P-OLED, AMOLED or SUPERAMOLED, it doesn't change) it is. This is due to a substantial difference between the two technologies. A difference that, by the way, is also found on TV screens: smart TVs with LED displays consume much less energy when used in dark mode.
Dark Mode: LCD Vs OLED
In an LCD screen all the light comes from a backlight panel. Each pixel acquires a color due to the polarization of one, two or all three sub-pixels (red, green and blue). This polarization is achieved by sending an electric current, which moves the liquid crystals by orienting them and letting light of a certain color pass through. To generate a black pixel, the liquid crystals are not "moved" and, consequently, block the light coming from the rear panel. But the back panel remains lit. That's why dark mode saves battery power with an LCD display, but the savings are minimal.
In an LED screen, however, each pixel corresponds to an LED (Light Emitting Diode). So when you need to draw a black pixel, that pixel simply stays off. That's why, unlike with LCDs, with LED displays the saving from dark mode is more pronounced.
How much battery can be saved with dark mode?
The battery saving from dark mode varies from smartphone model to model (and even from sample to sample), but there are very reliable tests to quantify it. On the YouTube channel PhoneBuff, for example, a very interesting test was done: a robotic arm performed a very long series of operations on two iPhone XS (so with OLED screen) absolutely twins, which differed from each other only because one was constantly in dark mode, the other constantly in light mode. The result was astounding: the battery of the iPhone used with dark mode active lasts 30% longer.