Every visit to the Netflix homepage generates 0.48g of CO2. According to Website Carbon, a calculator developed by Wholegrain, this makes the site “dirtier” than 72 percent of all websites globally. By comparison, the Greenpeace Germany website produces just 0.13g of CO2 per visit, performing better than 69 percent of websites worldwide.
Why are the CO2 emissions per page view so different? Regarding Netflix, the tool says: “It looks like this website uses standard energy.” This refers to the energy mix, which, in the EU, sits at around 50 percent non-renweable. Greenpeace, on the other hand, evidently runs its website on renewable energy. In short, the tool recognises and shares data about the website’s power source.
The model checks whether the hosting uses renewable energy. In other words, whether the website runs on green servers in a data centre. In order to do this, it accesses a directory from the Green Web Foundation. According to Website Carbon, if Netflix used green hosting, it would emit at least nine percent less CO2.
Hosting is only part of the story
When we calculate a website’s footprint, we have to look at the entire journey of a digital request. It isn’t just about the data centre; it includes the energy required to pull that data through global networks and the power consumed by the device in your hand. The end-user stage is actually the heaviest hitter: it is estimated that while data centres account for 22 percent and network infrastructure for 24 percent of emissions, user devices are actually responsible for 54 percent.
Ultimately, a site’s carbon impact is a tug-of-war between design and power. A website becomes more climate-friendly the leaner its design, reducing the work the device has to do, and the more it relies on green energy.
However, the real frontier isn’t just “lean design” or “green coding.” The focus is shifting toward carbon-aware and grid-aware websites. Rather than being passive consumers of power, these sites are designed to be “intelligent”. This means actively communicating with the energy grid to adjust their behaviour based on the availability of renewable energy.
Why do we talk about sustainability for websites at all?
To understand how we can move beyond simple hosting and into ‘intelligent’ web design, we spoke with Fershad Irani, digital sustainability consultant and web developer at the Green Web Foundation. “The technology sector overall is responsible for around 2–4 percent of global annual carbon emissions, a number which seems set to rise with the continued march of the artificial intelligence machine”, he recently told RESET.
“While the energy use and emissions of an individual website may be small in the grand scheme of things, as a whole web traffic is significant and continues to grow.” Video content and streaming, in particular, contribute massively to this growth. Consequently, the combined total of billions of daily page views creates a massive CO2 footprint for the digital world.
While many companies and developers already prioritise fast websites with good performance—which is usually only achievable through lean design—Fershad told RESET that there are aspects of sustainability beyond performance that need to be brought more sharply into focus. “Building resource-efficient websites is among these.”
From green hosting to carbon-aware websites
Relying on green hosting and lean websites is an essential start on the path to a more sustainable digital world. However, it doesn’t have to be the finish line. Beyond solutions that optimise the existing system, other approaches are opening up completely new possibilities.
One of these is the concept of carbon-aware websites. The idea is to programme digital services so that they respond to how CO2-intensive the electricity is when a page is accessed. In concrete terms, Fershad describes it as: “delivering core content when the grid is fuelled by dirtier energy, and enhancing the experience as the grid becomes cleaner.” If the electricity is particularly “dirty” at the time of access, a significantly reduced version of the website is loaded—meaning images might be hidden or highly compressed, alongside other layout adjustments.
Grid-awareness situates websites within the energy grid
The relatively new “grid-aware” concept from the Green Web Foundation goes one step further. The concept was born from the idea of better aligning the digital world with the overarching goals of the green energy transition. Decarbonisation is a key aspect, of course. But, it also encompasses “stability, resilience and equity” of the energy system as a whole. Designing a website to be grid-aware means taking into account key metrics of the surrounding power grid and adjusting its performance accordingly.
But how do websites know the state of the grid in real time? When a user visits a page, their location is determined via HTTP headers. Then, the current grid intensity is retrieved and compared with regional averages.
Fershad explained to us that for the “Grid-aware Websites” project, they used data from the startup Electricity Maps. “For this project, they also worked with us to develop a new data source which provides a more generalised, relative indicator as to whether a given energy grid has a carbon intensity that is ‘higher’, ‘around’, or ‘lower’ than average when compared to recent historical data.”
The “heavy lifting” of these adaptations is performed by edge computing technology. “That proves to bring with it a bit of a higher barrier-to-entry, as developers need to be familiar with these technologies,” Fershad admits. “We are hopeful that in the future, features can be built into platforms which extend our Grid-aware Websites project and make it a simple ‘one-click’ setup.”
Branch shows what a grid-aware website looks like
Screenshot of the Branch magazine homepage. I accessed the Branch online magazine website on a grey winter’s day in Berlin. Unsurprisingly, it appeared on my screen in a reduced mode. On the page, I found information stating that the electricity in my grid is currently “dirtier”—meaning more fossil-fuel based—than average. Images didn’t load; instead, I saw an attractively designed text version. If I still wanted to see the images, I would have to actively click a button on the placeholder. The website doesn’t load custom web fonts, but uses system fonts instead. These are fonts pre-installed on most devices. There were no animations running to ensure CPU usage was kept to a minimum. The colour scheme was dark.
Branch magazine, whose content revolves around the possibilities of a fair and sustainable internet, is an excellent place to see a grid-aware website in action. As you navigate through the site, something else becomes obvious: when we browse an internet that adapts to the conditions of our location, it’s suddenly stripped of its apparent immateriality. “Grid-awareness can encourage users to think about how their physical world interacts with their digital world in different ways,” Fershad adds.
The website for the Overbrowsing project aims for exactly this interaction between the digital and physical worlds. This grid-aware website was created by a research group focused on promoting sustainable web practices at the Institute of Design Informatics at the University of Edinburgh. If I access the site during a period of high local grid demand, images are deactivated and the layout is adjusted. Additionally, the visualisations are nature-reactive: the appearance of the website changes according to air pollution data. The higher the air pollution, the deeper the red of the background colour.
“We are hopeful features can be built into platforms”
But how do websites know the state of the power grid when we access a page? Fershad explains that “Grid-aware Websites enable the creation of dynamic online experiences that respond to the energy grid they are being used on – delivering core content when the grid is fuelled by dirtier energy, and enhancing the experience as the grid becomes cleaner.”
Fershad notes that for this project, they worked with the startup to “develop a new data source which provides a more generalised, relative indicator as to whether a given energy grid has a carbon intensity that is ‘higher’, ‘around’, or ‘lower’ than average when compared to recent historical data.”
The heavy lifting of website adaptation is performed by edge computing technology, which checks the state of the grid and modifies the webpage before it is sent back to the browser. “That proves to bring with it a bit of a higher barrier-to-entry, as developers need to be familiar with these technologies,” says Fershad. “We are hopeful that in the future, features can be built into platforms which extend our Grid-aware Websites project and make it a simple ‘one-click’ setup.”
Currently, Branch and Overbrowsing are among the few pioneers of this approach. To lower the barriers for others, the Green Web Foundation provides an open-source toolkit on GitHub and shares honest reporting on their own implementations. They deliberately avoid a “one-size-fits-all” solution, preferring a flexible approach that allows teams to make nuanced, context-specific design adjustments.
Can it overcome the obstacles?
However, challenges remain. “Right now, the biggest hurdle for the project is access to data to perform the grid-aware checks,” reports Fershad. While the Electricity Maps API is a powerful tool, access is currently limited to paid users. “We are working with Electricity Maps to make some amount of data available for free usage so that more people can adopt grid awareness on their websites.”
The possibilities for grid awareness are considerable in the backend
Branch and Overbrowsing are examples of front-end solutions, as only the data volume of the displayed web content is adjusted to the current power grid. However, the possibilities for grid-awareness in the back-end are also considerable. The core idea here is to increase the amount of clean energy used by digital infrastructure by being flexible about where or when digital services are executed. In the context of the energy transition, this is also referred to as load shifting. This could mean moving AI training and other computationally intensive processes in data centres to times and regions where the proportion of renewable energy is high.
“On the server side, a lot of work has already been done to dynamically shift processing tasks to cleaner regions,” says Fershad. This is no longer an issue. Google, for instance, states that it has been shifting workloads between data centres based on the availability of carbon-free energy since 2021. Microsoft has announced that Windows Update is now carbon-aware, while Apple has also taken initial steps in this direction with iOS version 16.1. “Projects like our own Grid Intensity Go library, Carbon Aware Scheduler, Carbon Aware KEDA Operator, as well as services from other organisations like Electricity Maps and WattTime, make this possible,” says Fershad.
However, for website servers, this kind of shifting is much more difficult. “While there are CDNs [Content Delivery Networks] that allow certain content to be hosted in multiple regions worldwide, for traditional website hosting, it is very complex to have multiple servers (and sometimes multiple databases) hosting a website while remaining synchronised.”
An internet in harmony with renewable energy production
Shifting computing power to regions and times where plenty of low-carbon electricity is available is an alternative to simply waiting for energy grids worldwide to become cleaner. The same applies to displaying websites in data-efficient formats as long as the power grid is carbon-intensive and heavily loaded.
The digital reality does not yet look like this. The web development industry is not particularly good at creating low-carbon websites. However, we might not have to keep waiting for the industry to finally take action. Fershad told us about ideas that the Green Web Foundation intends to pursue: “Imagine a browser where users can opt-in to grid-awareness, where pages and content are optimised to ensure they consume fewer resources on the user’s device. Or a CDN that delivers content to users from the ‘greenest’ node rather than just the nearest one.” And he invites collaboration: “If anyone out there wants to sponsor that, they should definitely get in touch!”
There are, therefore, many ways to achieve a grid-aware internet, whether through direct or sometimes more circuitous routes. And perhaps, eventually, we will arrive at an internet that not only causes fewer CO2 emissions but also follows a natural rhythm—moving away from a 24/7 world where everything is always open and possible, towards a digital ecosystem that has rest periods and follows the sun and the wind.
These approaches are also found in the concept of permacomputing. A very worthwhile article on this topic: Permacomputing – How the Concept of Permaculture Is Being Adapted to the Digital World
