How do people read houses energy labels?

We investigate how consumers process information displayed on Energy Performance Certificates (EPCs). Using a randomized artefactual experiment with 3000 French participants, we assess the impact of these labels on people's perceptions of a house's energy performance. Our findings reveal mixed effectiveness: while EPCs capture the attention of most participants, nearly 24% fail to notice them altogether. Among those who do, perceptions are influenced more by heuristic interpretations of the EPC's visually striking but potentially misleading design than by its underlying technical metric. At an aggregate level, perceptions align with Bayesian updating, as participants use the label grade to adjust their beliefs about energy quality. However, our results highlight significant limitations in the EPC's perceived reliability. These insights suggest replacing the EPC's technical metric with an estimation of the associated energy bill to foster greater consumer engagement and mitigate design-driven heuristics, alongside adopting direct measurement technologies to enhance the label's accuracy and trustworthiness.