Smart technologies provide diverse and promising opportunities for reducing energy demand and greenhouse gas emissions; they are increasingly expected to shift modern societies’ patterns of production and consumption towards sustainability. However, the existence of a theoretical potential does not imply that every smart solution (application of a smart technology) will actually contribute to sustainability. Policy-makers therefore need methodologies for evaluating the sustainability of smart solutions. This paper gives an overview of the current discussion in the field and the emerging methodological challenges. The challenges of assessing the direct impact of the ICT components and infrastructures are special cases of known issues in life cycle assessment methodology. The challenges of assessing indirect impacts are inherently interdisciplinary and call for integrated modelling approaches. The last two sections provide an overview of the papers assembled in this thematic issue that treat specific cases and general principles of modelling and evaluating the sustainability of smart solutions.