Towards qualification and quantification of repairability in residential electrical energy systems: The case study of LivingLab NRW

The energy transition in buildings is mostly evaluated by cost and greenhouse emissions, but this neglects other sustainability dimensions like resource depletion. Accordingly, factors like failure rates and repairability are relevant, as building energy components come from varied origins and have ad hoc assembly by local labour. The closest standards to measure repairability in this context are DIN 45554 and ISO 20887, but they lack the on-site system-of-system approach and an explicit evaluation score respectively. Therefore, this work aims to create a suitable evaluation system based on these standards. This is achieved with a multicriteria scoring system, evaluated by the research community via a survey and tested on two houses in Wuppertal. This component-indicator scoring matrix is additionally tested in sensitivity scenarios such as system boundaries or interpretations. The best evaluated components are the meter and battery (84%–89%), which are simple components with good documentation. Roof-mounted components are the worst evaluated (48%–60%) as they have reduced accessibility and require more preparation. Sensitivity analysis shows a maximal deviation of 3.5%, which does not change which house has a better score (72 vs 68%). Common weak spots are poor labelling or accessibility. Based on the limited number of installations examined, the scoring system seems stable. Further investigations should include additional experiments, professional interviews, and relating the score to monetary and environmental benefits, allowing the layperson to better interpret the benefits of repairability. Acknowledging its limitations, the indicators still help reduce mounting/identifying/dismounting challenges by highlighting subcomponents that can be simplified or standardised.