As the need for drastic reductions in global greenhouse gas emissions becomes increasingly urgent, governments and policymakers are developing proposals for climate change policies that aim to achieve net-zero emissions. However, the challenge lies in determining the most effective way to operationalize this transformation. While cost efficiency is often emphasized as a desirable property, experience shows that it is neither necessary nor sufficient to achieve a desirable policy portfolio. Instead, we advocate for a broader definition of economic efficiency: policies must also be feasible, fair, effective, and credible. Trade-offs between these criteria are common, and must be balanced to create a successful policy portfolio. The European experience provides interesting case studies with which to illustrate these efficiency dimensions and their implications.