The EU Emissions Trading System (EU ETS), which is a cornerstone of the EU’s policy to combat climate change, has been criticised by its effects on the competitiveness of intensive energy demanding industries, and in particular, of the chlor-alkali sector. The main chlorine application in Europe is the production of polyvinyl chloride (PVC) from ethylene dichloride (EDC) as intermediate. Since chlorine is mainly traded in terms of derivatives, the aim of this work is to assess the vulnerability of the European chlor-alkali industry to chlorine replacement by imported EDC. An Energetic, Economic and Environmental Sustainability Assessment (EEESA) methodology is proposed based on the main variables affecting EDC production. Moreover, the influence of the EU ETS compensation measures and the emission allowance price in the current (mercury, diaphragm and membrane) and emergent (oxygen-depolarized cathodes (ODC)) technologies is studied. The most vulnerable scenarios become mercury and diaphragm technologies due to energy consumption. However, the salt price dependency on the quality requirements substantially influences the EEESA results. This analysis also shows the importance of hydrogen valorisation, whose major impact is observed in ODC scenario.