In addition to designing and developing for well-being, equity and sustainability, SUI is based on 2 green mode design principles graceful degradation and user control.
Graceful degradation degrades performance of a software while retaining its core functionality. This way, it is possible to interact with the software through multiple alternative versions.
User control is a core UX principle that places user at center of user experience of an app. Hence, graceful degradation is optional to avoid violation of this fundamental principle.
Read more about green mode design
A proposal for a design paradigm to reduce emissions via user choice and progressive degradation - Green Mode Design.