Internationally, Stockholm’s brownfield development Hammarby Sjöstad is often seen as ”one of the world’s highest profile examples of Sustainable City Development” (Economist, 2011). To what extent do the district’s real estate owners and managers, residents etc. rely on smart infrastructure, to control energy use and its impacts? Does ICT integrate energy system components through automation, does it interact with its users, informing or persuading? This paper reports from an ongoing study, in which smart infrastructure is defined as infrastructure that makes it easy for users and managers of the Sjöstad buildings to keep energy use and its impacts low, without compromising utility or comfort. Data is collected from documents and interviews, which also served to identify the real estate units that have smart infrastructure. Previous evaluation indicates that the average energy performance of Hammarby Sjöstad’s buildings is no better than in similar buildings of the same period, but with a factor three dispersion. In all, about 5 per cent of the total number of flats in eight real estate units were found to have smart infrastructure, mainly to automatically integrate one or more novel components such as photovoltaics into the energy systems. In a few cases, buildings were provided with ICT that actively interacts with the system operators or the residents. Already from the first phase of development in 2000, the district was provided with a comprehensive fibre network, so the potential for smartness is there, but only in part utilised in the buildings. Thus there is a great untapped potential for “Renewing a New City” in terms of energy efficiency, if the local demand shapers – residents’ housing cooperatives and other real estate owners – are able to interest ICT providers to team up and form a suitable business model.