ESG Reporting: Making Sustainability in IT Measurable

The ongoing digitalisation of the economy is leading to an exponential increase in the energy consumption of IT systems. Current studies show that global information and communication technology is already responsible for around 4% of worldwide greenhouse gas emissions, a figure that could rise to 14% by 2040 if no systematic countermeasures are taken. With the introduction of the Corporate Sustainability Reporting Directive (CSRD) and the European Sustainability Reporting Standards (ESRS), the IT industry faces the challenge of systematically measuring, assessing and reporting its environmental impact. This article analyses the scientific foundations for developing Green IT metrics in the context of ESG reporting and examines established measurement methods for quantifying the sustainability of IT infrastructures.

Regulatory Framework and Methodological Challenges

The Corporate Sustainability Reporting Directive, which has been in effect for large companies since 2024 and will apply to further organisations from 2026, significantly expands reporting obligations compared with the previous Non-Financial Reporting Directive. For IT departments, specific compliance requirements arise that demand the systematic capture and assessment of the environmental impact of digital systems.

The European Sustainability Reporting Standards define concrete reporting content that includes IT-specific key figures on energy consumption, CO2 emissions and resource efficiency. The double materiality analysis requires IT organisations to assess both their direct environmental impact and climate-related risks to their business operations. This requirement presents IT leaders with the challenge of developing quantifiable metrics that can represent both perspectives.

Scientific Foundations of Emissions Measurement

The Greenhouse Gas Protocol as a Methodological Foundation

The Greenhouse Gas Protocol constitutes the internationally recognised standard for the capture and reporting of greenhouse gas emissions. For IT departments, the correct allocation of emissions to the three scopes is particularly complex: Scope 1 covers direct emissions from company-owned IT installations, Scope 2 relates to indirect emissions from purchased energy for IT operations, and Scope 3 accounts for all other indirect emissions along the digital value chain.

The strategic partnership between ISO and the GHG Protocol, announced in September 2025, creates for the first time a harmonised framework for emissions measurement. This development is of particular significance for IT organisations, as it establishes a unified methodological foundation for the sustainability assessment of technical systems and reduces the previous fragmentation of different standards.

Software Carbon Intensity as an IT-Specific Measurement Approach

The Software Carbon Intensity Specification represents a specialised approach to measuring the carbon intensity of software systems. Formalised as the ISO/IEC 21031:2024 standard, SCI defines a methodology for calculating the emissions rate of software systems using the formula: SCI = ((E x I) + M) / R, where E represents energy consumption, I the location-based emission factors, M the embodied emissions of the hardware, and R the functional unit.

This methodology enables IT organisations to quantitatively assess the environmental impact of their software and identify optimisation potential. Particularly relevant is the function-based approach, which allows assessment per user, transaction or API call and thus supports scalable sustainability evaluations.

Established Metrics for Sustainable IT Systems

Power Usage Effectiveness and Its Limitations

Power Usage Effectiveness remains the established standard for assessing the energy efficiency of data centres, defined as the ratio of total energy consumption to IT equipment energy. Leading data centres achieve PUE values of 1.06 to 1.2, while the industry average stands at around 1.8.

Despite its wide adoption, the PUE metric has conceptual limitations. Particularly problematic is the paradoxical deterioration of the PUE value when IT load is reduced through more efficient hardware. This weakness underscores the need for complementary sustainability metrics for a comprehensive assessment of data-centre performance.

Complementary Sustainability Indicators

The scientific literature identifies several complementary metrics for a holistic assessment of data-centre sustainability. Carbon Usage Effectiveness takes the carbon intensity of the energy sources used into account and is calculated as CUE = (Total Energy Consumption x CO2 Emission Factor).

Water Usage Effectiveness quantifies water consumption for cooling purposes, while Energy Reuse Effectiveness assesses the reuse of waste heat. These extended metrics enable a holistic assessment of data-centre sustainability that goes beyond pure energy efficiency and captures environmental impacts across multiple dimensions.

Green Software Engineering Metrics

Systematic literature analyses on Green Software Engineering identify various categories of sustainability metrics for software systems. These include energy-consumption measurements at application level, algorithm-efficiency assessments and lifecycle assessments for software products.

Current research emphasises the importance of resource-demand measurements as a basis for assessing the sustainability of software. Both quantitative methods such as energy-consumption measurements and qualitative approaches such as stakeholder surveys are used for comprehensive sustainability assessment.

Technological Implementation Strategies

Automated Monitoring Systems

The practical implementation of Green IT metrics requires automated systems for continuous data collection. Modern monitoring systems integrate energy measurements from various IT components, cloud platforms and infrastructure elements into central dashboards for management.

OpenTelemetry and Cloud Carbon Footprint tools enable the practical implementation of SCI measurement through the automated capture of energy consumption and functional units. This technological integration is essential for the scalable implementation of ESG reporting requirements in larger IT organisations.

Cloud Computing and Sustainability Assessment

Cloud computing presents both challenges and opportunities for IT sustainability. Hyperscale cloud providers typically achieve better PUE values and higher server utilisation rates than traditional enterprise data centres, which can lead to significant energy-efficiency gains.

At the same time, cloud usage requires a careful assessment of Scope 3 emissions and the integration of provider-specific sustainability metrics into the organisation's own ESG reporting. The complexity of emission attribution in distributed cloud environments poses a particular methodological challenge.

Systematic Challenges and Limitations

Standardisation and Comparability

The fragmentation of various Green IT standards and metrics represents a significant challenge for the comparability of sustainability assessments. The announced harmonisation between ISO and the GHG Protocol promises a unification of methodological foundations, but practical implementation will take time.

Particularly problematic is the lack of standardisation in assessing software sustainability, where different definitions and evaluation approaches can lead to inconsistent results. This methodological uncertainty complicates both internal optimisation efforts and external benchmarking processes.

Data Quality and Availability

Empirical studies show that many IT organisations have difficulties capturing high-quality sustainability data. In particular, the quantification of Scope 3 emissions in complex IT supply chains proves methodologically demanding and data-intensive.

The dependence on external data sources for emission factors and hardware specifications creates additional uncertainties in the assessment. Organisations must therefore develop robust data-quality processes to ensure the reliability of their ESG reporting.

Strategic Implications for IT Organisations

Integration into IT Governance Structures

The successful implementation of Green IT metrics requires systematic integration into existing IT governance structures. This includes defining sustainability targets at board level, establishing corresponding responsibilities and regularly monitoring progress through established IT controlling processes.

The challenge lies in balancing technical precision with management-appropriate aggregation of the available metrics. IT leaders must translate complex technical sustainability data into strategically relevant key figures that support decision-making at various organisational levels.

Technology Roadmap for Sustainable Transformation

IT organisations should develop a systematic roadmap for introducing sustainable technologies that takes both short-term efficiency gains and long-term transformation goals into account. This encompasses the migration to more energy-efficient cloud platforms, the optimisation of software algorithms and the implementation of Green Coding practices.

The prioritisation of measures should be based on a quantitative assessment of improvement potential, taking into account both technical feasibility and economic viability. Particularly important is the development of integrated approaches that systematically combine hardware, software and operational optimisations.

Future Perspectives and Development Trends

The convergence of sustainability and IT standards through the ISO-GHG Protocol partnership is expected to lead to a unification of methodological foundations. At the same time, advances in automation technology and artificial intelligence are enabling more precise and cost-efficient capture of Green IT metrics.

The development of sector-specific sustainability standards for different IT domains will further improve the relevance and precision of available metrics. Particularly important is the integration of lifecycle perspectives that take into account not only the operation but also the manufacture and disposal of IT systems.

Future developments are also expected to include the integration of real-time optimisation algorithms that automatically distribute workloads based on the current carbon intensity of the electricity grid, thereby enabling continuous emissions reductions.

Conclusion and Recommendations for Action

The systematic measurement and assessment of the sustainability of IT infrastructures is evolving from a voluntary corporate social responsibility activity to a regulatory necessity. The available scientific methods and technical standards already provide a solid foundation for quantifying Green IT performance today, but they require strategic and methodologically sound implementation.

IT organisations that invest early in developing comprehensive Green IT metrics will not only ensure regulatory compliance but also realise operational efficiency gains and strengthen their strategic positioning in an increasingly sustainability-oriented market environment. The challenge lies in the intelligent selection and integration of the available measurement approaches in line with specific organisational requirements and stakeholder expectations.

The continuous development of methodological foundations, particularly through the harmonisation of international standards and the integration of automated measurement technologies, will further improve the practicability and informative value of Green IT metrics. IT leaders should actively follow these developments and adapt their sustainability strategies accordingly in order to succeed in the long term.