Introducing Digital Carbon Ratings

Understanding the carbon impact of websites and other digital products is crucial to achieving a greener web. However, existing website sustainability ranking processes are both confusing and fall short of what’s needed for aggressive climate action.

Website sustainability must be:

• Rigorous: incorporate scientific methods into measurable sustainability outcomes
• Standardized: adhere to common and widely accepted measurement and reporting standards
• Understandable: easy for people who are new to this topic to comprehend

To address this, we propose a simple digital carbon rating system that follows these principles and aims to make website sustainability more intuitive and accessible for a wider audience.

By providing clear and transparent metrics, our goal is to encourage a global industry transition toward more sustainable digital products and services. Ultimately, this should reflect a global reduction in page size and corresponding emissions associated with the web overall.

Making Digital Sustainability Easier to Understand

Our open source methodology for calculating website carbon emissions combines data transfer with the carbon intensity of electricity to derive a standardized emissions estimate. This estimate can then be used as proxy data for more rigorous assessments of a digital product or service’s environmental impact. In other words:

• Data transfer is a core metric representing website energy efficiency (though it is not the only one).
• Reducing energy consumption is key to improving web sustainability. 
• There is benefit in helping digital teams understand how carbon emissions relate to data transfer. 

By prioritizing this in the rating system, we hope to encourage a greater focus on data (and therefore energy) efficiency.

Quantifying Website Sustainability Ratings

To determine a pass/fail threshold for website sustainability, we took inspiration from other rating and labeling systems using data from the HTTP Archive, which tracks how the web is built. 

By introducing this rating system, we aim to challenge the industry and foster progress. At first glance, it might seem challenging: 

• The pass/fail threshold represents the global average data transfer size of 2.4 MB, derived from the HTTP Archive’s data sets. In other words, web pages this size or larger will fail the test. This represents a significant portion of the internet.
• However, recognizing the urgent need for bold action to combat climate change, we intentionally set the bar high. In a rapidly warming world, websites exceeding emissions represented by the average page size cannot be considered sustainable. 
• We hope that this will inspire organizations to set more aggressive emissions targets and performance goals for their digital products and services.

This approach is necessary to successfully assess and improve website sustainability. It highlights the need to shift our focus towards designing low-emissions websites that prioritize the well-being of both people and the planet. 

Factoring in the Carbon Intensity of Electricity

While our carbon calculations methodology can be adapted to specific use cases with bespoke data, the rating system is designed to give a ‘like for like’ comparison between web pages. 

For this reason, the calculation uses the global average carbon intensity of electricity as standard, and adjusts this downwards for websites that are detected as using green energy in the data center. Therefore, the use of green hosting also contributes to a web page’s carbon rating in addition to data transfer.

Rating System Benefits

The new rating system offers several benefits:

• Standard Scale: First, it provides a universally recognized scale that enables digital product teams to understand how their website ranks against others.
• Setting Goals: It also facilitates setting goals and page weight budgets, allowing people to measure and improve progress over time.
• Communication: Moreover, the rating system’s simplicity enhances communication by making it easier to convey sustainability criteria. 
• Transparency: Finally, by removing the ambiguity associated with numbers, the rating system promotes transparency and encourages informed decision-making.

A Digital Carbon Rating Scale

Here’s how this rating system works:

Who Should Use This Digital Carbon Rating Scale?

As with our digital emissions measurement methodology, we encourage anyone to use this scale and provide feedback on how to improve it. Website and digital product teams should consider incorporating it into existing development processes. Also, we plan to improve the system over time as we learn new things. 

Applying Digital Carbon Ratings to Your Products and Services

The introduction of a standardized rating system for sustainable web design aims to simplify the process of understanding and communicating website sustainability. Here are several ways to incorporate it into your own work:

• Share it with organizational leaders to foster discussions about digital sustainability. 
• Use the system during discovery and roadmapping exercises to help project stakeholders better understand digital emissions.
• Incorporate it into existing design and development practices to match business goals and user needs with clear emissions targets.
• Use it to align digital projects with broader sustainability reporting initiatives.

By providing clear benchmarks based on real data, this digital carbon rating system empowers individuals and organizations to contribute to a more sustainable web. While aggressive, it can serve as a catalyst for industry-wide progress. We hope you will join us in embracing it as a tool for change.