We've long known that Dark Mode and Night Mode apps can extend the life of smart phones with OLED screens. This is true for Android, and it is true on the iPhone. This is because the individual pixels in dark areas of the screen need to work less and use virtually no juice when displaying real black. When recorded SlashGear Google repeated this during its Android Dev Summit this week, showing some slides that compare the power consumption of different colors. (The company used its original Pixel smartphone for these data points.)
You can see that white consumes the most energy by far. This led Google to realize that the popularity of white in its own apps and in the style guidelines of Android is by no means ideal. It is everywhere and that does not change with the revised material design by Google.
Fortunately, the company seems to recognize the value of the dark mode. YouTube and Android messages already have it, and Google is also adding the feature to their phone app and testing it on the Google mobile feed. Android can also be set to a dark theme for the quick settings pulldown and the app drawer, but Google has not yet gone so far as to add a system-wide night mode. (This is something that Samsung has in mind with its new One-UI.)
As an example of the dark mode used to save your battery, all you have to do is look at the big difference below, where the pixel is at 100 percent Brightness is set. The energy savings in the dark mode are obvious. I tend to stick to the traditional look of these apps because I find white text on black a little hard on my eyes, but it's nice to see that Google recognizes the value of all that white. Make a choice wherever it makes sense.