"Engineers know the theory but not what to change in code"

By 2022, the Green Software Foundation had trained tens of thousands of engineers through the Green Software Practitioner course. These engineers understood the principles: energy efficiency, carbon awareness, hardware efficiency, measurement. But a consistent question emerged from newly trained practitioners: “OK, I understand the principles — but what do I actually change in my code?”

The gap was real and specific. Early members like AVEVA and Mastercard recognised that “if we are to succeed in significantly reducing software’s carbon emissions, we need a knowledge base of trusted guidelines.” But when they audited what was available, one of the biggest challenges was finding resources — scattered across publications, articles, and videos — with no single trusted, peer-reviewed source of actionable patterns developers could apply to their codebases.

Measurement and theory were necessary but not sufficient. An engineer could calculate an SCI score but had no catalogue of proven interventions to improve it. The knowledge existed in fragments — individual blog posts, conference talks, internal wikis — but had never been consolidated, validated, and organised for practical use.

“As a CTO, every time I want to understand how to make my existing software applications greener, I need clear guidance on which applications to decarbonise and the priority patterns to implement — but lack of knowledge about how patterns apply to my applications gets in the way, and that means we end up making poor choices or we do nothing.” — User persona from the Design Thinking workshop