Introducing the Website Carbon Rating System

Written by Marketa Benisek - November 13, 2023

In today’s digital age, the internet is an integral part of our lives. It connects, informs and entertains us. However, it also carries a significant environmental cost. We created Website Carbon a number of years ago to provide a simple, free to use tool that would help people to learn about digital sustainability by visualising the environmental impact of web pages in an easy to understand format.

We’ve been working with industry partners to evolve the methodology and are excited to announce that we have now introduced a new rating system to hopefully make the results even easier to understand.

Why does the web need an energy rating system?

The internet’s carbon footprint is on the rise, contributing approximately 2-4% of global emissions — equal to or greater than the entire aviation industry. Websites are not just virtual entities; they’re part of a very physical infrastructure that powers the internet. They rely on servers, data centres and networks, which in turn require electricity to manufacture and operate.

We believe that awareness is the first step to positive change and so we’ve been exploring how we can leverage the popularity of Website Carbon to reduce website emissions.

Inspired by the energy efficiency ratings of household appliances, vehicles and buildings, we wanted to create a similar system for websites. Energy labelling has been effective in communicating varying levels of efficiency and the format of colour coded ratings is now well recognised in many parts of the world. That’s why we’ve chosen this medium as a way to inform, educate and inspire the creators and owners of websites to strive for better environmental performance.

What we aim to achieve

We set three key objectives for the new rating system:

1. Simplify understanding

Our first goal is to make the energy and carbon impact of websites accessible and intuitive for a wider audience. We believe that understanding the environmental impact of websites should not require a background in tech or sustainability. It should be as easy as reading an energy label on an appliance.

2. Standardised ratings

Our second objective is to create a clear and transparent rating system that drives the web industry toward a more sustainable and less wasteful future. We hope that this will encourage organisations to embrace more sustainable web design and development practices.

3. Challenge and progress

Our third objective is to challenge the industry and drive progress. We want to encourage web designers, developers and organisations to adopt more sustainable practices, reduce digital carbon emissions and collectively work toward a more sustainable web.

Website Carbon Rating Scale

Here’s how this rating system works:

RatingGrams CO2e per Pageview
F≥ 0.847
Website Carbon Rating Scale (CO2e emissions per Pageview)

* The Website Carbon Rating System is based on the Digital Carbon Rating System developed through the SWD collaboration. Visit for more details

What’s a good rating?

We set our benchmark for a good rating (A+ to E) as any site that falls below the global average CO2 emissions for desktop web pages. Ratings go from A+ (very efficient) to E (which is still better than global average). Any website with emissions that exceed the global average receives an F rating.

This is important because the internet emissions continue to rise every year due to the ever-increasing number of internet users and internet-connected devices. We are experiencing the effects of the changing climate all over the world, and if the energy consumption of the digital sector continues to rise at the current rate, we won’t be able to meet the net-zero targets set to avoid the worst effects of climate change.

By collectively shifting the global average, we can play our part in building a more sustainable internet for all.

So, aiming for a good rating isn’t just about improving your website; it’s about shaping the future of the web for a better world.

Why should you care?

You might be wondering how much difference this can make. Let’s take a look. 

An average website with 10,000 monthly page views emits about 31.5 kg CO2e (29 kg with green hosting) over a year. In contrast, a top-rated A+ website emits only 3.5 kg (3.2 kg with renewable hosting), reducing emissions by a staggering 89%. Just imagine how much energy would be saved if all organisations designed their websites with sustainability in mind. 

Sustainable websites not only reduce energy consumption but also enhance user experience, boost engagement and increase conversion rates. They load faster, provide smoother user journeys and offer greater reliability and accessibility. Therefore, a greener website benefits both your organisation and the environment, so you’re guaranteed a return on your investment.

Embracing progress

You might be wondering if all our own websites and clients’ websites receive an A+ rating with our new system. The short answer is no. The rating system has been designed with our partners to be intentionally challenging and ambitious in order to drive continuous improvement, even for us.

There are reasons why some websites are naturally more efficient than others, whether that’s because of their use case or their age. For example, a videographers portfolio website will naturally have more energy intensive requirements than a simple text based information website for your local council, so we should always consider the context when deciding what ‘good’ looks like. Similarly, we are constantly learning and improving the way we design websites to make them as efficient as possible.

We’re confident the new rating system will help us to keep pushing ourselves for higher standards along with the rest of the industry. It’s important to remember that perfection shouldn’t hinder progress. Progress is the name of the game. It’s more impactful to have millions of developers and designers building websites with sustainability in mind, even if they aren’t perfect, rather than just a handful striving for perfection.

Join us on this journey

We’d love for you to become a part of this journey toward a cleaner world where the internet is part of the solution, not the problem. You can test your website on Website Carbon, discover your rating and explore optimisation tips on our blog or in Tom’s book, Sustainable Web Design. You can also share your story by adding a Digital Sustainability statement to your site. And, as always, whether you require assistance, want to share your story, or explore our digital sustainability services, please don’t hesitate to contact us.

Special thanks to our industry partners

Our sincere thanks go out to our industry partners, especially Mightybytes, who have been instrumental in the success of the project. A special shoutout to Beleaf for their visionary proposal of the Website Carbon Rating System. Your innovative idea lights the way to a greener web and we’re incredibly grateful for your dedication to this mission.