In the promotion of sustainable consumer behaviour, it is important to establish a mental relation between one’s behaviour and its environmental impact. High hopes rest on timely feedback on personal energy consumption in order to create this link. Great efforts are being put into the development of information systems to achieve this, and smart meters are being deployed as an enabling technology worldwide. Recent smart metering trials, which provide feedback on aggregate household electricity consumption, report moderate savings of 2-5%. There is, however, a vivid controversy about consumer interest and continuous use of these technologies in the long run. This uncertainty introduces substantial risk to the deployment of these technologies, as the persistence of savings is crucial for the cost-benefit analyses and scalability of these programs. This paper investigates the long-term stability of the behaviour change induced by a real-time feedback technology. Our initial study found average energy savings of 22% for the target behaviour. In this study, we analyse 17,612 data points collected in a one-year follow-up field study. The results suggest that the effects of behaviour-specific feedback on energy consumption do not exhibit a significant decay, indicating that this kind of technology successfully induces persistent behaviour change.