Sustainability is no longer just a buzzword – its ecological, economic, and social impacts are becoming increasingly relevant in software development. As we’ve already explored in our previous article, software decisions can significantly affect hardware longevity.
In this post, we focus on an approach that makes the energy consumption of software itself and its related CO₂ emissions visible. The Software Carbon Intensity (SCI) standard, developed by the Green Software Foundation, helps developers and companies model the emissions of their applications and supports them in making more conscious decisions.
What is Software Carbon Intensity (SCI)?
SCI brings transparency to the environmental impact of software and provides a simple formula and clear methodology to estimate CO₂ emissions. The goal is to create an objective and repeatable foundation for making software more ecologically sustainable.
How SCI Works
SCI models the CO₂ emissions caused both during operation and in the creation of software. This includes energy consumption, hardware efficiency, and the energy mix. It gives developers the transparency they need to pinpoint the areas with the greatest potential for effective carbon reduction.
The core formula of SCI is:
In this formula, E represents the energy consumed by the software in kWh, I the amount of CO₂ per kWh consumed, and M the embodied carbon. (To learn more about what embodied carbon means and how it’s measured, check out our series on Embodied Carbon). The factor R normalizes these emissions per use, user, system runtime, or access – depending on the context and availability of data. In Germany, the average value for I in 2023 was 380 g CO₂/kWh (Umweltbundesamt, 2023). Further values and country-specific data can be found at electricityMaps or the IEA.
A practical example for measuring energy consumption is modeling via CPU and RAM usage. Alternatively, energy can be estimated using network load, number and type of processes, or standardized benchmark tests. The chosen methods must always be well-documented and reproducible to ensure transparency. A physical power meter isn’t strictly necessary – script-based tools like Apple’s “powermetrics” can reliably estimate actual hardware utilization.
An Internationally Recognized ISO Standard
Since 2024, SCI has been officially recognized as an ISO standard (ISO/IEC 21031:2024). It defines clear criteria and methods for transparently measuring and reporting the carbon footprint of software. As a result, it has gained international relevance and acceptance, making it easier to implement across the industry. Companies benefit from a globally accepted framework that enables consistent and comparable sustainability assessments.
Measuring is Winning
SCI allows companies to compare the environmental efficiency of different software solutions and make informed, sustainable choices. Developers integrate the methodology directly into their workflows, leading to more resource-efficient products in the long term (Green Software Foundation Projects, 2024). Solid data is essential here – because you can only improve what you can measure. SCI provides this data, creating the foundation for real transparency and actionable sustainability in software development.
Challenges and Criticism
Implementing a new standard comes with its challenges. Accurate measurements rely on high-quality data, which can be time-consuming to collect. To make SCI truly effective, it needs to be put into practice and backed by real-world examples. Even rough estimates are enough to trigger improvements and identify the most impactful areas for reducing emissions.
Conclusion
The Software Carbon Intensity standard sets a new benchmark for sustainable software development. With clear, measurable outcomes, it empowers organizations and developers to take meaningful action on emissions. Now it’s up to the industry to adopt the standard and drive real change for a more sustainable digital future. For more insights into hardware-related emissions, check out our series on Embodied Carbon.
