Green Requirements Engineering

In times of increasing digitalization and growing environmental challenges, the topic of sustainability is becoming a focus in the software development process as well. This affects not only the infrastructure, but also the way we formulate software requirements. Green requirements engineering (Green RE) deals with precisely this question: How can sustainability aspects be systematically and measurably integrated into requirements elicitation and specification?

Green RE refers to the systematic recording, specification, and implementation of requirements aimed at environmentally friendly, energy-efficient, and resource-efficient software development and use. This involves not only functional requirements, but above all non-functional requirements (NFRs) that affect, for example, energy consumption, CPU utilization, or CO₂ emissions.

Key terms in Green RE:

• Green coding: sustainable programming, e.g., through efficient algorithms.
• Green operations: resource-efficient operation of software.
• Digital environmental footprint: the CO₂ equivalent or environmental impact of a digital product.

In the software life cycle, requirements engineering (RE) is the very first opportunity to consider sustainability aspects and actively plan for them.

The earlier sustainability goals are defined and translated into requirements, the more effectively negative impacts on the environment can be avoided. Conversely, later interventions in the code base or infrastructure often involve significantly higher costs. Green RE enables sustainability to be systematically considered from the outset—as part of both functional and non-functional requirements.

In the context of software, sustainability encompasses five key dimensions that can be explicitly considered in requirements engineering

• Ecological sustainability: Reduction of energy consumption, resource usage, and CO₂ emissions through efficient operational and architectural requirements.
• Economic sustainability: Promotion of cost efficiency and long-term benefits through reusability, low maintenance costs, and investment security.
• Social sustainability: Ensuring accessibility, fairness, and usability – e.g., through barrier-free design or linguistic and cultural diversity.
• Technical sustainability: Focus on longevity, maintainability, and adaptability of systems—e.g., through modular architecture, good documentation, and technological stability.
• Individual sustainability: Consideration of the cognitive load and well-being of users through transparent, respectful, and non-manipulative user interaction.

These dimensions provide a sound basis for formulating Green RE in a systematic, structured, and targeted manner.

However, it should also be noted that trade-offs often arise in this context.

In the practical implementation of Green RE, trade-offs between the five sustainability dimensions often arise. The conflict between economic and ecological goals is particularly pronounced: energy-saving or resource-efficient solutions are often more technically complex or require higher initial investments.

These conflicts cannot be completely avoided. Therefore, an important part of Green RE is to consciously identify, document, and evaluate them with stakeholders. Trade-offs are thus not an obstacle, but an integral part of sustainable requirements work. Methods such as scenarios or trade-off analyses help to make the effects of different options transparent and to find a solution to potential conflicts.

Sustainability aspects can be integrated into classic RE activities in a targeted manner.

• Gather: Questions about environmental compatibility and energy efficiency should be asked as early as the requirements elicitation stage. Stakeholder interviews, workshops, and questionnaires can be specifically expanded to include sustainability aspects, such as "What environmental goals should the system support?" It is also important to identify sustainability stakeholders at this stage.
• Analyze: During the analysis, trade-offs between sustainability and other quality requirements (e.g., performance, usability) can be identified and weighed up. It is advisable to model sustainability as an explicit goal.
• Document: Requirements should be documented in such a way that sustainability aspects are measurable and testable, e.g., as NFRs with specific limit values or thresholds.
• Validate: The validation should ensure that sustainability-related requirements are comprehensive and suitable for consensus. Review checklists or sustainability scenarios are also useful in this context.
• Manage: Green requirements should be versionable and traceable – in particular so that their implementation can be tracked throughout the course of the project. Metrics such as CO₂ reduction per release can help to quantify progress.

A useful tool for the structured integration of sustainability aspects into the RE process is the Sustainable Awareness Framework. This framework supports RE teams in systematically developing awareness of the environmental, social, and economic impacts of requirements. It offers a collection of questions, criteria, and decision-making aids that can be used in workshops or reviews. The aim is to promote a sustainability-oriented mindset among both stakeholders and the project team, and to take sustainability aspects into account from an early stage and on a consistent basis.

Example of a user story with sustainability goals

User story: As the product manager, I want the backend system to automatically switch to a power-saving mode when idle in order to reduce energy consumption.

Acceptance criteria:

• Power-saving mode is activated when CPU utilization is < 10% for 5 minutes.
• In power-saving mode, energy consumption is reduced by at least 30%.
• Active user transactions are not interrupted.
• The changeover is logged in the monitoring system.

The topic of green IT and sustainable software development is becoming increasingly important – also in Switzerland. Companies recognize the relevance of ecological aspects, but many still lack operational implementation.

Status quo:

• Sustainable IT has been discussed extensively in recent years and is now considered an important contribution to ecological sustainability in companies.
• However, in practice, there is often a lack of established tools and clear metrics for systematically implementing sustainability goals.
• Initial green performance indicators are being developed (e.g., energy consumption per transaction)
• New market entries with specialized and AI-supported solutions are now opening up concrete ways to automatically record sustainability metrics – which will make green requirements engineering much more practical and operationally robust. However: The use of AI can be helpful in measuring sustainability metrics, but it must also be taken into account that AI systems require more computing power and thus also consume more electricity and hardware. Here again, a trade-off arises that needs to be specifically evaluated and analyzed. This scenario suggests that green RE also interacts closely with the infrastructure and systems used.
• In addition, software development and operations teams are becoming increasingly aware of green coding practices and energy optimization.
• Accessibility: Since 2025, the European Accessibility Act (EAA) has required manufacturers and providers to make digital products and services—such as websites and apps—accessible in the EU. This EU regulation also affects Swiss companies that provide products or services in EU markets. This strengthens the "social" aspect and requires concrete, barrier-free requirements already in the RE process.
• Keyword ESG: ESG (Environmental, Social, Governance) is an assessment framework that requires companies to be transparent about their environmental, social, and corporate ethical impacts. In Switzerland, binding ESG reporting requirements for large companies have been in force since the 2023 calendar year and must be fulfilled for the first time in 2024 (according to Art. 964a–964c OR). These regulations aim to disclose sustainability-related information such as CO₂ emissions, social risks, and compliance structures. For requirements engineering, this means that requirements must be documented, traceable, and verifiable in such a way that they enable ESG-compliant products and services.

Despite its growing importance and methodological advances, green requirements engineering faces various limitations in practice:

Cloud-based systems: Many modern applications run on cloud infrastructures where resources are allocated dynamically. Even if a software solution is designed efficiently, this has only a limited impact on the energy consumption of the entire data center, which continues to run independently.

Increased energy consumption due to AI: The use of AI – for example, for usage analysis, automation, or sustainability measurement – can be helpful, but it also entails high computing loads. This results in a trade-off that must be evaluated depending on the context.

Dependence on infrastructure conditions or decisions: green RE can formulate efficiency requirements, but can only be effective if infrastructure decisions – such as scaling (e.g., Kubernetes) or hardware efficiency – are also taken into account. Sustainability does not arise solely at the requirements level, but through the interaction of architecture, operations, and organization.

These limitations show that Green RE is an effective tool for raising awareness and defining requirements in a structured way, but it is no substitute for a holistic sustainability strategy.

Green requirements engineering is a topic of growing relevance. Companies are increasingly recognizing that sustainability aspects in the software lifecycle are not only a social concern, but also offer strategic opportunities.

Green RE should by no means be seen as a substitute, but rather as a supplement that should be taken into account in all RE activities—with the aim of taking ecological effects more consciously into account and developing more resource-efficient solutions in the long term.