The world is urbanizing rapidly and under the business-as-usual scenario, energy needs in cities will also increase dramatically. Urban population is expected to double by 2030; however the global built-up area is expected to triple during the same period (Angel et al. (2005) [1]). This building out instead of building up will dramatically increase energy requirements and costs of new infrastructure and will influence the link between cities and climate change; to this end, the timely monitoring. of the built-up area features and dynamics is considered supportive for defining temporal and spatial changes in energy needs and thus facilitate changes in urban design and support adaptation and mitigation plans in cities for climate change. In this paper the capacity of indices based on Earth Observation, to support the assessment of the built-up area features and dynamics is discussed and assessed. It is found that such indices can provide timely and accurate depiction of the built-up features and dynamics, including urban sprawl. It is also found that built-up area dynamics relate to the spatial and temporal variation of the discomfort index; this is an important parameter for defining urban energy needs as the higher the discomfort index, the more demanding the energy needs for cooling. (C) 2014 Elsevier B.V. All rights reserved.