Dark Mode Might Be Burning More Juice Than You Think

Using apps and websites in dark mode can actually use more energy than standard mode, according to researchers, as it causes people to crank up the brightness.

This counterintuitive finding is claimed by BBC Research & Development (R&D), which says that despite the popular energy saving recommendation to cut electricity consumption by switching to dark mode, doing so might actually make things worse.

"Dark mode is a popular dark-theme colour content scheme and research has found that, for some devices, switching to dark mode can reduce device power consumption. Energy conscious internet users are therefore encouraged to browse in dark mode," say the authors of a BBC R&D blog post.

"The catch is that the advertised energy savings haven't been tested in the wild, where user behavior can cause unexpected consequences."

So the BBC's R&D engineers put participants in front of the BBC Sounds home page and asked them to adjust the device brightness until they were comfortable with it, repeating this for both light and dark mode versions of the page.

BBC Sounds in regular and dark mode

Unfortunately, 80 percent of participants turned the display brightness up significantly when they were viewing the dark mode version. Raising up the brightness level increases energy use, say the engineers, labeling this outcome as a kind of "rebound effect" that ought to at least challenge the notion that dark mode saves power.

Not content with overturning this assumption, the team investigated whether more responsive websites are more energy efficient, and found there was no correlation, concluding: "developers cannot therefore simply optimize for performance and hope that energy savings occur as a happy by-product."

The team also examined whether the amount of data transferred over the internet from a website could serve as a direct proxy for energy consumption, and again only a low correlation between the two was found.

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"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," says BBC R&D engineer Zak Datson, one of the blog authors.

"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," he adds.

Datson also published the team's findings in a short paper available here [PDF].

For climate-conscious web users, or just those looking to minimize their energy use, the Beeb team recommends lowering the brightness on your phone or laptop, and switching to a smaller device may also help conserve energy.

Next: how turning down your lights at home actually makes the room brighter! ®