This study investigates the impact of revealing the changes in daily residential energy consumption of individual households on their respective house faç ades. While energy feedback devices are now commercially available, still little is known about the potential of making such private information publicly available in order to encourage various forms of social involvement, such as peer pressure or healthy competition. This paper reports on the design rationale of a custom-made chalkboard that conveys different visualizations of household energy consumption, which were updated daily by hand. An in-situ, between-subject study was conducted during which the effects of such a public display were compared with two different control groups over a total period of 7 weeks. The competitive aspects of the public display led to more sustained behavior change and more effective energy conservation, as some graphical depictions such as a historical line graph raised awareness about consumption behavior, and the public character of the display prompted discussions in the wider community. The paper concludes with several considerations for the design of public displays, and of household energy consumption in particular.