Dark mode's battery advantage proven: Save energy with a simple switch

The screen is a crucial component of any smartphone, but it also consumes the most energy. Manufacturers claim that the device's standby time can be counted in weeks, but when displaying even relatively simple content, it is significantly reduced, often to just a few hours.

Is there any way to deal with the high energy demand? The simplest solution seems to be to use the screen less frequently, but we don't buy modern smartphones just not to use them.

You can reach interesting conclusions when you think about what the display is currently doing. In the screenshot provided, all essential elements, such as graphics, text, buttons, and icons, occupy less than 30 percent of the screen area. The remaining space is a white background.

The problem is that this background has practically no functional role. Up to 70 percent of the screen lights up just to make the other elements visible. Wouldn't it be ideal if the background didn't consume energy?

As it turns out, more efficient use of the screen area is possible. LCD screens have a constant, uniform backlight over the entire surface, independent of the displayed colours. On the other hand, OLED displays work differently. They are equipped with organic diodes that allow each of the millions of points on the screen to function independently. The brightness of each single pixel can be adjusted separately.

Besides offering high-quality images, OLED panels have another crucial advantage: energy efficiency. Pixels responsible for deep blacks are not activated, meaning they do not consume energy.

Remember the mentioned 70 percent of the screen area that lights up uselessly? If we reversed the colours and changed the white background to black, only the displayed elements would consume energy on an OLED screen, which would be less than one-third of the display area.

In the experiment below, two pairs of screenshots of the website were prepared using a smartphone with a 4.5-inch OLED screen and a 4500 mAh battery—one with a white background and the other with a black background.

Each pair of screenshots was turned into a slideshow, displayed continuously until the battery was completely drained.

The test started with a fully charged battery at 100 percent in both cycles. During the tests, the smartphone had no external applications, operated in airplane mode, and had the screen brightness set to maximum. This ensured that any differences in energy consumption would be due only to the colour scheme of the displayed content, especially the background colour.

The smartphone ran out of battery:

• after 10 hours and 25 minutes in light mode;
• after 13 hours and 31 minutes in dark mode.

These results speak for themselves. After enabling dark mode, the smartphone lasted 3 hours and 6 minutes longer, which is a 29 percent increase.

Recall that in both cases, the same texts and identical graphics were displayed. The nearly one-third extension in operating time was solely due to the change in background colour.

A slower battery drain means the phone needs to be charged less often. Less frequent charging means less energy consumption, which in turn reduces coal burning.

It is estimated that OLED screens will be featured in up to 75 percent of smartphones introduced to the market.

In computers, the energy-saving advantages of dark mode are more minor due to the lower popularity of OLED screens, but they are not entirely insignificant. Dark backgrounds are easier on the eyes, allowing for laptop use in lower lighting conditions at night.

Dark mode used by a large number of smartphone users can indeed lead to significant energy savings.