Define the system boundaries

[chrisn]

There is an assumption in the guidelines that saved time converts into emissions savings. In one example of many, https://w3c.github.io/sustyweb/#assess-and-research-visitor-needs says:

which will help reduce emissions as developers will spend less time building a product with unnecessary features

This is only potentially true if we consider a system boundary that stops at the immediate concerns of a given website (or its development), and does not consider developers' or visitors' existences beyond that point. For example, a developer may move onto another project rather than switch off their computer or the lights in their office; a website visitor may be browsing to fill time and move onto the next website.

Similarly, https://w3c.github.io/sustyweb/#rigorously-assess-third-party-services contradicts this by recommending that you "create your own clickable icons and widgets, rather than relying on third-party services to host or allow embedding within your product or service". Should we assume from this that emissions resulting from data transfer are considered to be greater than the emissions generated by developer time? What criteria or metrics should we use to make such a decision?

The system boundary should be clearly stated when looking at what effect the guidelines will have. Consideration is important when assessing the overall effect of a change on a system and potential rebound effects (see Earles & Halog).

We suggest defining clear system boundaries that your guideline works within, be clear about the limitations of this, and to avoid making assertions where there isn't adequate proof or certainty.