Member Story
"How do you measure software's carbon footprint?"
How Abhishek Gupta, Henry Richardson, Navveen Balani, and contributors from across the industry built the Software Carbon Intensity specification — a rate-based metric that became ISO 21031:2024 and is now used by banks, consultancies, and infrastructure operators to baseline and reduce their software emissions.
Organisations involved
ISO
The SCI achieved ISO 21031:2024 status — an internationally recognised standard
7+
Independent implementations with published results across banking, consulting, and infrastructure
15.1%
Average CO₂ saved per application at Autostrade per l'Italia across 60 applications
< 3 years
From alpha release to ISO standard — a process that typically takes five to seven years
The Problem
Carbon totals existed — but engineers couldn't see the impact of their own code
Organisations had been reporting carbon totals annually for years, but those numbers lived in sustainability reports that engineering teams never saw. A CTO could quote the company’s total Scope 2 emissions, but couldn’t tell an individual developer whether the software they’d just shipped was better or worse for the climate than the version before.
The existing GHG Protocol gave compliance but not insight. The world of carbon measurement was, as Abhishek Gupta described it, “splintered in its methodologies and tooling with very few widely accepted standards, especially for computing systems.” A developer could spend weeks optimising code for energy efficiency and see no change in the company’s reported carbon total — the number was too aggregated, too annual, and too disconnected from the software itself.
No single company could solve this alone. The problem required a standard that worked across industries — banking, travel, consulting, telecommunications — and across technology stacks: cloud, on-premises, serverless, desktop. It needed buy-in from competitors who would agree to measure the same way. That meant a coalition.
“We envision that SCI measurement will become a standard part of every developer’s toolbox and the norm in the future.” — Navveen Balani, Co-Chair, Standards Working Group and Impact Framework (April 2024)
The Journey
From a fragmented measurement landscape to an ISO standard in under three years
Crafting the standard
2021
When the Green Software Foundation formed, Abhishek Gupta volunteered to co-chair the Standards Working Group alongside Henry Richardson of WattTime. The team's key insight: make the SCI a rate, not a total — carbon emissions per functional unit (per API call, per user, per request). This meant the SCI could work across every software domain, every use case, and every person. Critically, the specification excluded offsets — the only way to improve your score was to genuinely reduce emissions.
Read the original SCI crafting article →Alpha release for public comment
December 2021
The Foundation released the alpha SCI specification, inviting the global software community to test it. The specification accounted for carbon awareness, energy efficiency, and hardware efficiency, and required standardised, transparent reporting of what went into the calculations. At this point, the co-chairs acknowledged the biggest barrier was "a dearth of case studies."
Read the SCI specification project article →First case studies validate the approach
2022
Texas State University evaluated the SCI against foundation AI models — GPT-J 6B, GPT-Neo variants, GPT-2 — and concluded it was an effective metric for evaluating carbon impact at the inference stage. Their research found that carbon-intensive models don't necessarily yield better quality: GPT-Neo 1.3B consumed only 27% of the energy of GPT-J 6B while producing comparable answers.
Texas State University deems the SCI an effective metric →Enterprise implementations at scale
2023
Accenture became one of the first organisations to calculate an SCI score for a production application: 0.025 gCO₂ per API call across 890,000 monthly requests. At UBS, Pindy Bhullar's team applied the SCI to two on-premises banking applications — one in Investment Banking, one in Asset Management — documenting operational emissions, embodied emissions, and scaling by functional unit. NTT DATA Italy partnered with Intesa Sanpaolo to build a real-time monitoring dashboard showing SCI scores across the bank's entire IT infrastructure.
Read the Accenture SCI implementation case study →ISO standard status
March 2024
From alpha release in December 2021 to ISO 21031:2024 in March 2024 — the SCI became an internationally recognised standard in under three years. For context, ISO certification for a software specification typically takes five to seven years. GSF's consensus-driven process, combining open community review with direct enterprise participation, compressed that timeline without compromising rigour. CAST demonstrated that fixing just ten green code deficiencies with four person-days of effort could reduce annual CO₂ emissions by an estimated 400 kg and save over 1,000 kWh per year. Autostrade per l'Italia, working with CAST, achieved an average of 15.1% CO₂ savings across 60 applications.
Read about the SCI achieving ISO standard status →Abhishek Gupta's legacy
Ongoing
Abhishek Gupta, co-chair of the Standards Working Group from GSF's formation, passed away on 30 September 2024. He had driven the SCI from inception through to ISO certification. As Asim Hussain wrote: "He leaves a powerful legacy with the Software Carbon Intensity Specification. His tireless efforts over the years led to a consensus on the specification, which was later published to ISO in late 2023 and is now being adopted globally." Sara Bergman of Microsoft added: "Working on the very first versions of the SCI with him continues to be one of the proudest moments in my career."
Read the tribute to Abhishek Gupta →The 'per R' is the secret sauce to the SCI. It is what makes the SCI into a tool that works for every software domain, every use case, and every person.
GSF, SCI Alpha Release, December 2021
Who came together
The people who made it happen
Abhishek Gupta
Founder and Principal Researcher
Montreal AI Ethics Institute
Co-chaired the Standards Working Group from GSF's formation and led the SCI from inception through ISO certification. In memoriam — passed 30 September 2024.
Henry Richardson
Senior Analyst
WattTime
Co-chaired the Standards Working Group, bringing grid-oriented expertise that shaped the carbon awareness dimension of the SCI.
Navveen Balani
Managing Director and Chief Technologist
Accenture
Co-chaired the Standards Working Group and Impact Framework, and led the first enterprise SCI implementation case study — measuring 0.025 gCO₂ per API call on a production Accenture application.
Sanjay Podder
Global Managing Director
Accenture
Co-founder and steering member of GSF, and Chairperson at the time of ISO achievement. Championed the SCI as the foundation for industry-wide adoption.
Pindy Bhullar
ESG Technology and Sustainable Technology Lead
UBS
Led step-by-step SCI application to two UBS banking applications, producing one of the first published financial services SCI case studies.
In their words
"What can be measured can be managed. "
Abhishek Gupta
Montreal AI Ethics Institute / BCG
"SCI specification provided a practical methodology to baseline carbon emissions of the application, including embodied emissions and reducing the same. "
Navveen Balani
Managing Director and Chief Technologist, Accenture
"Reaching this milestone represents a collective effort from GSF member organizations. This achievement unlocks the potential to achieve industry-wide adoption of the SCI Specification, which is crucial in empowering organizations to achieve real-world emissions reductions. "
Sanjay Podder
Accenture and GSF Chairperson
Related articles
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Software Carbon Intensity (SCI) Specification Achieves ISO Standard Status, Advancing Green Software Development
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