EU climate policies should be pursued as cost-efficiently as possible. Costly measures make the green transition less likely to succeed in the long run and unnecessarily reduce EU competitiveness. Even while observing the subsidiarity principle, the global externality of climate change leaves ample room for policy action at the EU level. In fact, the EU possesses by far the most efficient instrument for climate policy: the EU Emissions Trading System (ETS). This article identifies key reform opportunities for the ETS and other EU climate-related policies. It argues that by streamlining the ETS and removing redundant regulatory measures, the EU can minimise the economic costs of the green transition, improve the efficiency and market orientation of EU climate policy, and strengthen productivity.