How to visualize electricity consumption anomalies: The impact of chart types on triggered emotions and eye movements

Abstract

Home Energy Management Systems (HEMS) show anomalies and unusual patterns of the electricity consumption of households, usually in the form of charts. Charts that show anomalies are very difficult to design in a way that is both comprehensible and visually appealing to users. However, visually appealing charts direct the users’ gaze to the central chart elements and thus trigger positive emotions, which in turn increase the intention to use HEMS. Therefore, this study focuses on the emotions and eye movements that different chart types showing anomalous electricity consumption trigger. An experimental eye-tracking and facial expression study was carried out with 50 participants that were randomly assigned to one of three commonly used chart types (bar, line or rose chart). The participants had to complete three search tasks during which the eye movements and the facial expressions were observed. The results show that different emotions are triggered depending on the chart type. Participants showed the highest number of sad and contempt facial expressions while viewing bar charts. Line charts triggered the most positive and, overall, the least negative facial expressions, followed by the rose charts. Bar charts triggered the most negative emotions among all three chart types. Although most eye-tracking metrics in this study differed by chart type, most results did not show significant differences. However, the later participants saw the area in demand in the rose charts, the sadder facial expressions occurred. HEMS providers can use these findings to design emotionally appealing charts for potential users, which in turn can increase their motivation to use these systems.