We have long known that dark mode / night mode apps can extend battery life on smartphones with OLED monitors. It's true on Android and it's true with the iPhone. This is because the individual pixels need to do less work on dark areas on the screen, and they use almost no juice at all when they show real black. Like SlashGear retrieved, Google repeated this on its Android Dev Summit this week, showing more slides comparing power expression in several different colors. (The company used its original Pixel smartphone for these data points.)
You can see that white removed uses the most power. This led Google to recognize that the appearance of white across its own apps and the Android style guidelines is well, less than ideal. It's everywhere and it does not change with Google's Revolutionary Material Design.
Fortunately, the company seems to recognize the value of dark mode. YouTube and Android Alerts already have it, and Google also brings the feature to their phone app and tests it in mobile Google feed. Android can also be set to a dark theme for the drop-down menu and app tray, but Google has not yet gone so far as adding a system-wide night mode. (Something Samsung plans to do with its new One UI.)
As an example of dark mode that comes to battery rescue, just look at the big difference below, where Pixel is set to 100 percent brightness. Power saving in dark mode is clear. I usually stick to the traditional look of these apps most often, as I find white text on black a bit hard on my eyes, but it's nice to see that Google recognizes the value of lightening on the white. Make it a choice where it makes sense.