The EU Emissions Trading Scheme (ETS) is a climate policy that's still not fully set. A model called DART was used to predict how it might affect trading, prices, and economies. The simulations showed that for emissions cuts to be cheaper, there must be a good balance in how emissions are divided among sectors. Giving fewer emissions to ETS sectors could save money. Also, countries joining the ETS can help make emission cuts cheaper by offering low-cost options, even if they don't sell extra emissions. So, a balanced division of emissions and the involvement of new countries are key for cost-efficient emission reductions under the EU ETS.