Gathering 22 partners from the EU, Norway, Switzerland and Ukraine, iDesignRES aims to provide public authorities and network operators with open-source toolboxes allowing to plan and to optimise the uptake of low and zero emission energy sources at regional, national and European scales. With these open-source tools, iDesignRES provides latest multi-physics component energy models, comprehensive energy system modelling (in particular assembling of component models), long-term multi-carrier grid planning and optimisation of investment and operation. i-DesignRES embraces a new degree of openness, transparency and accessibility to use energy system models and their components. It delivers a harmonized data structure compatible with all modelling approaches (i.e., standardized in a common modelling language). i-DesignRES relies on an already built database compliant with these standardized data formats. Based on this modelling and data infrastructure, iDesignRES will develop a unique and innovative cloud-hub platform to run any energy system model online. This will facilitate research collaboration (easier software testing and version control), and increase computational performance (open licenses, cloud services and supercomputing) for average users. To demonstrate and validate the tools, i-DesignRES has five real life cases: two macro region cases (North Sea area and South East Europe), two industrial clusters (Basque and Lombardy regions), and one expansion case in Ukraine. The models and scenario results are combined in the final iDesignRES visualisation tools aimed to inform policy makers and grid operators. The outcome is that the public and relevant authorities can design a renewable energy system entirely online with easily accessible suite of tools, capable to: model at high spatial-temporal resolutions (sub-hourly NUTS level2 regions), to represent detail energy system physics, and to assemble models with a high degree of modularity.