The EU proposal on liberalisation of the energy market has been widely debated in policy, stakeholder and academic circles both for its content and the potential consequences to the gas and electricity markets. However, little has been said about the empirical evidence produced by the European commission to support this legislative package. No research effort has been devoted to analysing the impact assessment document that accompanies the third legislative package. Since the impact assessment system has been in place, there have been concerns regarding quality and adequateness, especially when considering alternative policy options, including stakeholder opinions and quantifying costs, benefits and risks. This paper analyses how these crucial issues were factored into the impact assessment on the third legislative package. It investigates the interaction between the legislative proposals on energy liberalisation and its Impact Assessment.