The upcoming European Emissions Trading Scheme (ETS) is one of the more controversial climate policy instruments. Predictions about its likely impact and its performance can at present only be made to a certain degree. As long as the National Allocations Plans are not finally settled the overall supply of allowances is not determined. In this paper, we will identify key features and key impacts of the EU ETS by scanning the range of likely allocation plans using the simulation model DART. The analysis of the simulation results highlights a number of interesting details in terms of allowance trade flows between Member States, of allowance prices, and in terms of the role of the accession countries in the ETS. An important finding about the impact of the new ETS with respect to achieving emission reductions more efficiently, i.e. at lower cost, is that savings can only be realized if the cap on emissions is distributed between the ETS sector and the rest of the economy in such a way that the different abatement costs are taken into account. This would imply a relatively small allocation of emissions to the ETS sector. The second important result concerns the role of the accession countries. Even if they do not supply their hot-air in the ETS market, they contribute substantially to the cost savings of the ETS by offering low cost abatement options.