Smart city projects and experiments have dramatically increased in recent years. This is particularly the case in Japan where dozens or even hundreds of initiatives have been introduced this decade. Many discourses highlight the key role of individuals in smart cities, and there is a growing literature dealing with citizen participation. This article contributes to the discussion concerning the place of individuals in so-called smart cities while focusing on a different issue, namely behaviour change. This issue, while closely associated with the specific pattern of participation that is “coproduction”, is indeed a central objective of many smart city projects. This is especially the case in Japan where four Smart Communities were introduced by the government in 2010 and have served as a means for experimenting with measures for behaviour change. Thus, Japanese smart cities constitute a tool for governing household energy consumption. I argue, however, that this was not part of the objectives before the Fukushima disaster of March 2011 and the subsequent liberalisation of energy markets. Indeed, Smart Communities initially focused on economic and technical issues rather than reducing energy consumption. As well as Fukushima, behaviour change methods implemented in the US also play a key role in the governing of household energy consumption. On the one hand, economic advisors of the Japanese government learnt and applied the methods of the US Department of Energy in this area. On the other hand, the stakeholders of Smart Communities also imported behaviour change techniques from the US in order to deal with new issues raised by the Fukushima disaster and its consequences.