Scope 3 ISO14064 CO2/GHG calculation methodologies are designed for evaluating a businesses true emission's and take into account an organisations energy useage as well as evaluating suppliers (upstream) and user's energy inputs (downstream). Our calculations mirror this methodology and assign values to up and down stream energy useage. However, as no website's digital journey is identical either up or down stream we estimate energy useage based on the Sustainable Web Design Model (SWDM) guidelines.

Webserver (Hosting) energy useage varies according to the server and it's workload. Servers typically operate within a range of 150 - 1500W, however, in the vast majority of cases they host multiple websites, this figure varies according to site and useage. A servers performance is also affected by the ambient temperature and therefore servers need to be cooled. Air conditioning can, depending upon the environment, effectively double the server's energy demands. 

Some web hosting companies are making headway in terms of reducing energy useage and relying on sustainable energy sources. Where we know that a host is utilising renewable energy we will reduce the energy input within our calculations to reward clients who are consciously choosing a 'green' host.

Content Distribution. As users navigate your website they download more data, images, text, download files, and upload information. This data is distributed and stored on Content Delivery Networks as well as by your Internet Service Provider. The energy required to store and transmit your websites content is estimated to be slightly larger than the energy demands from web hosting. The SWDM emission calculation model is based on the volume of data that is transferred through the network as well as the host and therefore is a truer reflection of real energy useage for website to end user.

Ultimately it is the users that engage with the website and the efficiency of their devices impacts energy useage considerably. A mobile device will use far less energy than a laptop with a widescreen monitor attached. Our calculation methodology once again over-estimates average useage by assigning a user value based on energy hungry versions of the devices. However we then tailor the calculation based on the device split for your website users. 

Page size and views impact the calculations, as these influence the volume of data passed through the internet. Pages that include primarily textual content or well optimised images use far less energy than pages which contain auto-play video content. We include page size within our calculations so our clients are asked to contribute less for websites that are efficient and require lower power inputs through the hosting, distribution and used engagement process. We effectively reward clients for low energy useage rather than just providing an average.

We include variations in the calculations based on the International variations in CO2e output for the respective national grid. Different countries have varying CO2e outputs based on their reliance on sustainable and fossil fuel use. For instance the United Kingdom produces 0.225 Kg/CO2e per kWh whereas the USA produces 0.356Kg/CO2e per kWh. Our methodology ascribes the national value to where the site is hosted and is adjusted based on where the majority of users engage.

SWDM acknowledge there are arguments for calculating CO2e emissions in a different way. We are confident that the methodology is a fair over-estimate of useage and emissions and it enables us to reward efficient sites and therefore encourage lower emissions across the board.