Research: Device dark mode uses more energy than light mode
February 19, 2025
People who think they are saving energy by using dark mode rather than light mode on their apps and websites are actually using more energy, according to research from BBC Research & Development (R&D). The vast majority of people using an app or website in dark mode turn the brightness of their device up far higher than when they use the same thing in light mode.
Devices such as mobile phones and laptops are the largest contributor to media-related emissions, and some previous studies have shown these use less energy in dark mode than in light mode. But to test how people actually use dark mode in practice, BBC R&D sat participants in front of the BBC Sounds home page and asked them to turn up the device brightness until they were comfortable with it. Participants repeated this for both light and dark mode versions of the BBC Sounds page.
Of those tested, 80 per cent turned the brightness up far higher to better see the screen in dark mode, creating what’s called a ‘rebound effect’ and using much more energy than the supposedly more wasteful light mode option.
Zak Dakson, BBC R&D engineer, commented: “It’s great that lots of us are looking for ways we can be more environmentally friendly. But some of the most common sustainability recommendations are overly simplistic, to the point that many simply don’t work in the way they’re intended – or in the case of dark mode, actually end up using more energy. What we need is a better understanding of what exactly causes our devices to consume energy when we spend time online. That’s what our team is working on, so that we can make changes based on evidence that will allow us to reduce the overall footprint of digital media consumption, both here at the BBC and for the wider media industry.”
The findings are part of ongoing work by BBC R&D investigating how effective sustainability guidelines designed to help people build low energy websites and apps are – the initial findings of which have been documented in the academic journal Nature Electronics.
BBC R&D has recommendations for climate-conscious web users to reduce energy usage:
- Turn down brightness – using a phone, laptop or TV at full brightness can use as much as twice as much power as one at low brightness. Keeping brightness to a minimum saves energy, and helps prolong the battery life of portable devices.
- Use smaller devices – browsing on an external monitor connected to a laptop will consume more energy than browsing on a laptop alone, and browsing on a phone or tablet less energy still. Likewise smaller TV screens will naturally use less energy than larger ones.
- Use existing devices for longer – every device manufactured has an ‘embodied’ environmental cost, from mining the raw materials to the factories that put them together. Keeping old devices for longer can help to reduce the number of new devices that need to be manufactured and help reduce our total material and carbon footprints.