Why are dark websites so ugly

Dark themes save massive amounts of electricity on smartphones

As part of a lecture at the Android Dev Summit, Google developer Chris Barnes addressed a topic that smartphone users like to discuss: the power consumption of the display and, above all, the influence that the choice of color has on it. And in doing so, he provides specific figures that also put some of Google's own decisions in a critical light.

First of all, Barnes makes it clear that all of this is really just about OLED screens. Because only with these is each pixel illuminated individually, so that a black pixel does not consume any electricity. In the case of classic LCDs, on the other hand, this is different: Here the background lighting needs most of the electricity, so only the selected brightness has an influence on the electricity consumption and not the displayed content.

Concrete numbers

This difference can also be expressed in numbers: While the power consumption of the AMOLED of a Pixel 1 at maximum brightness of 250 mA is comparable to the LCD of the iPhone 7 (230 mAh), this changes suddenly when you switch to night mode. Here, the power consumption of the Pixel drops to 92 mA - a minus of 63 percent - while that of the iPhone remains the same. All figures were determined with a screenshot from Google Maps in the respective modes, as the aim was to prevent the operating system from influencing the measurement. In any case, it is clear that the dark display has a massive impact on the power consumption of the display. This is particularly relevant because the screen usually requires the most electricity in a smartphone, as Banes emphasizes.

Color choice

But the investigation also provides other interesting details: For example, it turns out that not all colors consume the same amount of power - although this naturally depends on the respective structure of the OLED. In the case of the Pixel 1, a completely blue screen at full brightness consumes 800 mW, while a green-filled display only consumes 580 mW. Red is just off the mark with 600 mW.

The biggest power guzzler, however, is of course white, as this is generated from all these partial colors. But this is exactly the color that Google has preferred for its designs for several years, as Barnes admits. This is also the reason why more and more Google apps are currently receiving dark themes, some of which can also be activated automatically with the battery saving function or the time.

Exemplary

Google has also examined the effects of such dark themes in detail: For example, a paused YouTube video with a light user interface consumes 239 mA while this value is reduced to 96 mA in dark mode. However, this example shows that the really big savings can only be achieved with full brightness. The power consumption of the display is reduced to 93 mA at 50 percent brightness even with a light theme. The dark mode then pushes the whole thing again to 80 mA, but the percentage difference is of course much smaller.

At the same time, it must of course be emphasized that the choice of a topic is not just based on electricity consumption. For example, black text on a white background is usually the best to read variant - and this is especially true in very bright environments, where a dark theme would theoretically help most to save energy. Nonetheless, these figures show that the availability of a system-wide dark theme makes perfect sense - something that Google has so far only delivered very fragmentarily on its own devices.

In addition to the little swipe at its own designers, the Google lecture has another reason, of course: The Android manufacturer wants to motivate the developers to offer even dark themes for their apps as an alternative. (Andreas Proschofsky, November 9, 2018)