Green IT and dark mode in the fight against climate change

In our mission is to help people make smarter choices for themselves and society. One part of this is to make it easy to choose alternatives that result in lower CO2 emissions. For some time, I have been thinking about whether there is anything I can do in my daily life as a developer to contribute to this mission/in this area, beyond my normal tasks of developing the product. I set out to do some research, and what I found was a wealth of simple steps you can take in all areas of IT to help reduce CO2 emissions. In this post I will focus on one of them, namely encouraging users to choose dark mode.

You might remember the hype around dark mode when it became widely available a few years ago. Using app colours that were mostly dark with bright text seemed superior in almost all areas. One of the proposed benefits was reducing energy consumption of apps and mobile phones. Even though the dark mode hype has died down, does it actually hold any potential for energy savings? Let’s take a closer look.

Mobile phones produced after 2017 mostly come with OLED screens. When they display black colour, the individual pixels are turned off and do not consume any power. Other dark colours will only consume a small amount of energy compared to brighter colours. This is in contrast to phones with an LCD screen that has to rely on backlight as LCDs do not produce their own power. If you want to learn more about this, iFixit made a youtube video explaning the difference between OLED and LCD screens.

Researchers at Purdue University have developed a tool called a Per-Frame OLED Power Profiler (PFOP) to precisely measure power consumption. On four different android phones, they tested six of the most downloaded apps on google play in dark and light mode and at a variety of brightnesses. Most people probably use auto-brightness, which will regulate screen brightness based on how bright the surroundings are. A majority of the time, it will put the screen brightness to about 30–50%. At those levels, the Purdue researchers found that using dark mode saves 3–9% battery consumption of light mode. They also found that the brighter the screen was, the higher the savings were. On a summer day when the sun is glaring at your phone and the brightness is set to 100%, draining your phone battery, choosing dark mode over light mode will save up to 47% battery power.

Throughout a normal day, users of your app will go through a variety of screen brightness needs. Catering to those needs in dark mode will make the user more likely to prefer dark mode at all times. Therefore it is important to take the same amount of care when making the dark mode version of a screen as the light mode version. It’s also important to give the users an easy way to opt in for dark mode.

Saving battery is not only beneficial to the individual user and their satisfaction. Increasing the time before a phone has to be recharged will also prolong battery life. As a result this can extend the time the phone is in use before it is replaced. Saving energy also has greater impacts. With a large enough user base, even saving just 3% battery power can result in large energy savings in total.

Striving to be more energy efficient, and making energy efficient products and services, is a good thing, even here in Norway, where most of our electricity comes from hydropower and is considered to be green. Electricity that we are not using, can be exported to other markets where green energy is less available, replacing electricity that would otherwise come from fossil fuel consumption.

We in see that making a good dark mode experience, and encouraging users to choose dark mode, can be one area where we can contribute to reducing CO2 emissions. Is there anything you do to combat CO2 emissions in your company? We would like to hear about it in the comments, big or small. If we see that this is a topic that interests people, we might write more about it. To learn more, you can read the research paper from Purdue University.

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Iselin Neteland

Iselin Neteland

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