Using Android's dark mode improves battery life, Google confirms
The colors and brightness of your screen play a significant role in battery drain.

Android P has its own dark mode.
Google hosted its 2018 Android Dev Summit on Friday, in which it talked about all things Android. In one of its presentations, Google talked about power consumption and how your phone drains its battery life. During this presentation Google shared an interesting conclusion: dark mode saves battery life on Android.
Sure, some people may have already been operating under that assumption. But the information and research Google shared give good context and may help you save your phone's battery.
Pixel versus iPhone 7 battery drain.
Google compared the amount of current (in milliamperes, or mA) the Google Pixel and iPhone 7 suck up when displaying a screenshot at max brightness (shown above). While the amount of current is comparable for the two phones, the number drops by 63 percent when using the Pixel with max brightness in dark mode.
Current usage by color with max brightness.
Google also broke down how much current is being used by different colors when the Pixel is set on max brightness. Its data shows that the color white uses up the most current, with blue coming in second. Black uses up the least amount of current. Red and green are close to tied and on the low end of the spectrum, using up about half as much current as blue.
Google then measured how power (in mW) is affected by pixel color. Results show which colors and combinations of colors use up the most power.
Blue still ranks highest in power consumption (compared to red and green on their own).
This data tells us two useful things: First, that dark mode or night mode will significantly lower how much battery your phone uses. Second, that the colors on your screen also make a difference. So if you want to save battery, you can turn on dark mode or swap the color balance to use less white/blue light (kind of like how Night Shift on iPhones turns your screen into the warmer end of the color spectrum).
There's a moment during Google's presentation where it admits that it's been pushing Android developers to use more white as their primary color for layouts. Google's research implies that this makes Android apps more power-hungry. Android Pie has a dark mode that may counteract this, however.
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