San Francisco, California, USA
#00162
Case study of
#00168 Standardize a single comparable carbon metric per unit of software work
Implementer
Green Software Foundation (a Linux Foundation project)
Location
Description
The Software Carbon Intensity (SCI) specification reached ISO accreditation as ISO/IEC 21031:2024 in Q1 2024. It defines software carbon as a rate: SCI = (E × I) + M per functional unit R, using a rate rather than a total and a consequential, marginal accounting stance that excludes market-based offsets. Reported adopters include AVEVA, Microsoft, NTT DATA, and UBS. NTT DATA Japan paired SCI with the CNCF Kepler project to build a carbon-aware Kubernetes scheduler that routes workloads to the lowest-carbon available location; NTT DATA Germany built an accelerator to compute SCI before and after applying Green Software Patterns. The main practical limitation is that developers often lack hardware specification and amortisation data needed for the embodied (M) term, making the metric apply more cleanly to whole applications than to isolated code sections.
Funding
Lessons learned
- Expressing carbon as a rate per functional unit rather than a total is what makes scores comparable across teams, vendors, and time — a design decision baked into the SCI formula itself.
- ISO accreditation (ISO/IEC 21031:2024) provides a citable definition that allows independent tools to produce interoperable numbers.
- The embodied-emissions term (M) is the practical bottleneck for adoption: developers rarely have access to hardware amortisation data, so teams should plan for whole-application scope rather than isolated code sections.
Sources
2Documented Jul 13, 2026