Estimated page impact: 0.41g CO2e per page view
So the first step (in the old adage of what doesn’t get measured, doesn’t get done) is to understand what impact your current website has.
At the moment I calculate this using a pretty big spreadsheet. The below video gives an overview of that spreadsheet. We compressed this video using mp4 because that gives better compression than webm, it went down from 80mb to 3mb without any discernible difference in the quality.
It lists every URL on a site, the number of annual page views (not unique, actual) and the weight of that page. Multiplying the page views by the weight gives you the total data transferred in a year.
From that, you can work out the KwH needed to transfer that amount of data. This is a crucial step of the calculation that is something I wish there was more consensus on (and I am working towards). At the moment I use the logic from Wholegrain Digital which takes the total amount of data transferred around the internet and the total amount of electricity the digital industry uses (minus the electricity needed to manufacture devices), figures which are available from two different reports.
From that, you can then use a carbon intensity figure (thankfully the UK’s is available for free, but sadly most other governments have monetised this data) to work out the carbon a website is responsible for.
And this is where the calculation can get very interesting. If your website has traffic from a few key countries you can use different intensities for the relative parts of your data transfer. Remember, data centres are only part of the problem when looking at electricity generation. All the switches, routers, devices etc make a very significant part of the electricity usage. You can even look at how your website is being transferred to a device; for example, mobile data is more energy intensive than wifi.
This calculation can be used for anything really, you just need to know how many data transfers there are and what their size is. I’m working on measuring the impact of ads delivered to a site, with the plan to start looking at the impact of data transfer for AI.
Microsoft’s sustainability calculator will help to massively improve calculation transparency but it only works for the high level PowerBI/Azure licences and obviously means you would need to move your site to Azure to use it. But if the current opacity from data centre providers (which is driven by a paranoia that competitive advantage will be lost) continues we will have to continue using these calculations and estimates based on what data we can get.
How about your wider IT impact… well that’s a subject for another day.
Have you read our previous article on how websites cause emissions? The next instalment in this series is on identifying content and design solutions.