The partners of the project are 3 cities with similar characteristics, experience and policies in specific sustainable use and production of energy and very ambitious carbon and energy reduction targets, aligned with Europe’s targets. In each city, initiatives to reduce energy inefficiency are already in place; however each of them has been aimed at a specific sector objective, while overlooking the impact that may be causing on other sectors. This is why all the stakeholders and city systems are considered so important when undertaking measures aimed at improving sustainability to make this an integral part of their urban planning in order to achieve best results in less time and will less cost.For this reason, these cities have decided to join together to improve efficiency along all the key aspects of their energy value chain, by applying smart city concepts in an integrated manner while learning from each other’s expertise and viewpoint in applying sustainable practices. The partners are experts on Energy (FSS, SANSEBASTIAN, TECNALIA and ACCIONA), ICT (BRISTOL, UNIBRISTOL and ARUP) and Mobility (FLORENCE, SPES and ATAF).To get the proposed objectives STEEP project will create a process model based on systems thinking for district energy master planning, which will be applied to 3 city districts to better understand the systems impacting upon energy use and interventions which can be taken to meet the ambitious energy and carbon targets. These models will be enriched and validated through open innovation methodologies applied with the stakeholders. The learning obtained from the process model for district energy master planning, then, will be applied at the definition of specific action plan (time line, the costs and pay-back periods) at city level. With the knowledge gathered in this process, it will be developed a replicable open source methodology and Key Performance Indicators for developing and screening integrated Smart City Plans.