What Transformer Early-Replacement Models Teach Us: Functional and Communicative Design Principles for Impact-Assessment Tools

Transformers play a key role in the European energy transition by reducing network losses and enabling the integration of renewable electricity. Early replacement of inefficient transformers can contribute significantly to energy savings, but its net impact depends on local conditions and needs to be quantified with suitable decision-support tools. This paper reviews seven existing tools that address transformers or closely related products, assessing them with a combined framework covering general characteristics (target group, granularity, scope, implementation), functional design (task-fit, user-fit, context-fit) and multimodal understanding (localisation, orientation, hierarchisation, navigation, framing, sequencing).

The analysis reveals two main user groups—industry stakeholders and policymakers—and shows that there is no transformer-specific tool to estimate the impacts of early replacement policies at EU stock level. Good practices include the use of IEC and Ecodesign standards, dynamic and context-specific data, minimal mandatory inputs, layered complexity and clear visual framing (e.g. consistent shading of input cells and error highlighting). Common pitfalls include limited methodological transparency, over-aggregated outputs and multimodal weaknesses such as inconsistent colour schemes, poorly labelled graphs and unclear sequencing.

Based on these findings, we identify a gap in the tool landscape, the absence of a transformer-specific tool to estimate impacts of early replacement policies at EU stock level and derive general recommendations for user-centred tool development. These include anchoring calculations in recognised standards, combining layered inputs with scenario comparison, and embedding multimodal design principles from the outset. The study demonstrates how functional and multimodal perspectives can jointly guide the assessment and development of more robust decision support tools.