Dark mode: Boosting smartphone battery life by up to 29%

The screen is a key component of every smartphone, but at the same time, it is one of the most energy-consuming. Manufacturers claim that a device's standby time can be measured in weeks, but displaying even low-demand content significantly shortens it, often to just a few hours.

Is there any way to deal with the high energy demand? The simplest solution seems to be to rarely turn on the screen, but we didn’t buy modern smartphones not to use them.

Considering what the display is currently doing, you can come to interesting conclusions. In the attached screenshot, all important elements, such as graphics, text, buttons, and icons, occupy less than 30% of the screen surface. The remaining space is a white background.

The problem is that this background has practically no functional use. Up to 70% 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 screen space is possible. LCD screens have fixed, uniform backlighting across the entire surface, which is independent of the displayed colours. OLED displays, on the other hand, work entirely 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 pixel can be adjusted separately.

OLED panels offer high-quality images but also have an important advantage: energy savings. The pixels responsible for deep blacks are not activated, which means they do not consume energy.

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

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

Each pair of screenshots was then turned into a slideshow that was displayed continuously until the battery was depleted.

Both cycles started with a full 100% battery charge. During the tests, the smartphone had no external applications, operated in airplane mode and had the maximum screen brightness set. This ensured that differences in energy consumption would only result from the colour scheme of the displayed content, particularly the background colour.

The smartphone discharged:

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

These results speak for themselves. After turning on dark mode, the smartphone lasted 3 hours and 6 minutes longer, an increase of 29%.

Remember, in both cases, the same texts and identical sets of graphics were displayed. The nearly one-third increase in operating time was solely due to the change in background colour.

Slower battery drain means the phone needs to be charged less often. Less frequent charging means lower energy consumption, which in turn leads to a reduction in coal burning.

OLED screens are estimated to be equipped in up to 75% of smartphones introduced to the market.

In computers, the energy-saving benefits of dark mode are less due to the lower popularity of OLED matrices, but they are not entirely insignificant. Dark backgrounds are more pleasant for the eyes, allowing laptop use in lower lighting at night.

Dark mode, used by many smartphone users, can contribute to significant energy savings.