This report lays out the modelling approach that is implemented in the POTEnCIA modelling tool (Policy Oriented Tool for Energy and Climate Change Impact Assessment) and describes its analytical capabilities. POTEnCIA is a modelling tool for the EU energy system that follows a hybrid partial equilibrium approach. It combines behavioural decisions with detailed techno-economic data, therefore allowing for an analysis of both technology-oriented policies and of those addressing behavioural change. Special features and mechanisms are introduced in POTEnCIA in order to appropriately reflect the implications of an uptake of novel energy technologies and of changing market structures, allowing for the robust assessment of ambitious policy futures for the EU energy system. The model runs on an annual basis with a typical projection timeline to 2050.JRC.J.1-Economics of Climate Change, Energy and Transpor