If people who are only listening to videos don’t have images playing, companies like YouTube might make themselves more Earth-friendly, a new study finds. That’s because a lot of the energy used to get that video to your eyeballs happens at the network and device level.

By sending only sound to users who aren’t watching, the company could reduce its annual carbon footprint by the equivalent of about 300,000 metric tons of carbon dioxide per year. That’s about the same amount of the greenhouse gas produced by 30,000 homes in the UK every year, according to a University of Bristol press release.

People watch a billion hours of YouTube every day, and each of those views sucks up energy. There’s your phone or computer, the internet or cell network that carries the video to you, and the servers at data centers that host videos and send them on their way. Companies like Google (YouTube’s parent company) have focused a lot on making the latter more energy efficient and on buying up renewable energy to offset the massive amounts of carbon dioxide produced by dirtier energy sources, like coal or natural gas, that often power their data centers.

People watch a billion hours of YouTube every day

Corporate efforts to make the digital pipeline more environmentally friendly tend to focus on these data centers, Chris Preist, lead author of the study and professor of sustainability and computer systems at the University of Bristol, explains in an email. “But we could see that the impact of digital services spreads beyond that,” Preist says.

Preist and his colleague Dan Schien first started looking at the carbon footprint of digitally focused companies in 2011, with a project focused on the carbon footprint of news organization The Guardian. After The Guardian project, Preist and his colleagues decided to zero in on YouTube.

Google had already publicly released data about YouTube usage, giving the researchers a great starting point. They were also really intrigued by one particular way that people use YouTube: to listen to music in the background while they’re doing other things online. Sending video to computers takes energy, but if people aren’t watching, that energy becomes what Preist calls “digital waste.”

the equivalent of 10 million metric tons of carbon dioxide

Yanking back 300,000 metric tons of carbon dioxide per year is big, but it’s still only a fraction of the total energy that we invest in getting videos to our phones and computers. By comparison, the researchers estimated that, in 2016, streaming videos on YouTube produced the equivalent of 10 million metric tons of carbon dioxide. (The Verge emailed YouTube for comment but did not hear back as of press time.)

There are a few caveats. First of all, the researchers didn’t have access to YouTube’s internal data on energy usage, so all of their numbers are estimates and are focused only on data from 2016. It’s incredibly difficult to measure a carbon footprint directly, so scientists are often forced to estimate how much carbon is produced by different activities. In this case, the authors went with more conservative estimates, assuming, for example, that people mostly watched videos on lower-resolution settings (which use less energy). Because of that, “our figure is very likely to be an underestimate of the actual footprint.” Preist says.

Also, the research doesn’t look at how much carbon was produced during the manufacturing process of computers, phones, and servers — all the hardware that makes streaming possible. “This is important and valuable work,” Preist says of hardware’s environmental impact. “But it’s not directly relevant to our key question: how can climate change consideration be factored into the design and running of digital services?”

Preist thinks that the burden of reducing streaming’s carbon footprint should rest on the companies that host and stream the content, not people tuning in to makeup tutorials, music videos, cooking shows, and vlogs.

“It is really important that the service designers take responsibility.”

“For global digital services, they have large footprints because billions of us use them. Our individual footprint is small.” Preist says. “It is really important that the service designers take responsibility for measures which can reduce the overall footprint, rather than individuals feeling they need to ‘cut down’ for environmental reasons.”