There is still significant potential to improve energy efficiency in all sectors and levels where measures can be applied. Facing the often cited “energy efficiency gap”, even the profitable potential is not fully exploited. Highlighting and quantifying the additional values of energy efficiency measures and investments considering the multiple non-energy impacts could help closing this gap and facilitate energy-relevant decisions and policy-making. The project "MICAT – Multiple Impacts Calculation Tool" is coordinated by Fraunhofer ISI (DE) together with the European partners IEECP (NL), Wuppertal Institute (DE), WiseEuropa (PL), E3 Modelling (GR), IIASA (AT) and ICLEI EURO (DE). The goal of MICAT is the development of a comprehensive approach to estimate Multiple Impacts of Energy Efficiency. MICAT will enable analyses at three different governance levels (local, national and EU) to address a broad target group and interested actors. This allows simplified analyses to be carried out on the basis of different data and policy scenarios in order to compare and assess the relevance of the multiple impacts. The project thus sets a sound scientific empirical basis for monitoring Multiple Impacts while providing a publicly available and easy usable online tool (MICATool) which has been developed in a co-creational manner with the respective governance levels. The national and local cases for monitoring Multiple Impacts of Energy Efficiency will be developed further in a broad stakeholder and dissemination approach to set a standard for future reporting on Multiple benefits.