What’s worse for the planet? Driving to the supermarket for your weekly shopping or spending all day on Zoom calls while binging The Office on repeat? Now, finally, we have an answer. Sort of.

For the first time, Netflix has revealed specific details about its carbon footprint. Using a tool called DIMPACT, developed by researchers at the University of Bristol, Netflix claims that one hour of streaming on its platform in 2020 used less than 100 g CO2e (million metric grams of carbon dioxide equivalent)—that’s less than driving an average car a quarter of a mile. For people binging Netflix, that’s useful context—but for the streaming giant, it provides crucial data to help it reduce its vast carbon footprint.

“The BBC, or Netflix, or any other provider, can’t just connect a power meter to the infrastructure and find out how much carbon was released into the atmosphere,'” says Daniel Schien, one of DIMPACT’s creators and a lecturer in computer science at the University of Bristol. And this is where DIMPACT comes in.

The tool, which is partially industry-funded, is essentially an elaborate calculator built to help digital media companies map and manage their carbon footprints. There are four modules, each representing different sectors—video streaming, advertising, publishing, and business intelligence. In Netflix’s case, Schien explains, the video streaming module consists of a superset of all the processes that Netflix would find in its organization: a simulation of our favorite show reaching us from a data center, for instance.

The benefit here is that DIMPACT can give detailed information on a company’s Scope 3 emissions—that’s the pollution caused by suppliers and customers. “For media companies, if you’re involved in entertainment, then Scope 3 would be the upstream production of films,” explains Christian Tonnesen, a senior partner at Carnstone, an independent management consultancy involved in the project. “And downstream it would be you delivering the media content, and also people consuming that content. So any company in the media sector that is setting a science-based target now has to get a good understanding of these Scope 3 emissions.”

Cutting emissions is essential if Netflix is to reduce its carbon footprint. In this regard, Netflix has lagged behind its competition. In January 2020 Microsoft promised to go carbon-negative by 2030; later that year, Apple announced its own plans to become carbon-neutral by the same date. Facebook has also committed to net-zero emissions from all suppliers and users, and Google has promised to run on exclusively renewable energy. In contrast, as The New York Times pointed out last month, Netflix has not announced targets for reducing emissions, despite saying it wants to reduce its impact on the climate.

These new figures are an attempt to rectify this situation. Netflix says it will release a white paper to validate its findings at the end of March and will reveal its climate targets this spring. For now, it has used DIMPACT to work out that one hour of streaming is equivalent to a typical 75-watt ceiling fan running for four hours in North America or six hours in Europe, or a typical 1,000-watt window air conditioner running for 15 minutes in North America or 40 minutes in Europe. “My first impression about that claim is that it seems reasonable,” says Bernardi Pranggono, a senior lecturer in computer network engineering at Sheffield Hallam University. But streaming, he explains, matters comparatively. So what might people do instead of sitting at home watching The Office on Netflix? If they went outside for a walk, this would be greener. But if they drove for 30 minutes to go to the cinema, it wouldn’t.

The tool lets Netflix identify emissions hot spots so it can redesign its services to make them greener. TV shows streamed by users in the UK could be hosted by data centers in the UK, for example. Or devices could be switched off more quickly if nobody is watching what’s being streamed. Netflix will also be able to speak to other companies in its supply chain—such as Amazon Web Services, which it uses for hosting—to help reduce emissions.