The study, initiated in June 2023, evaluates the Regulation on the Governance of the Energy Union and Climate Action. It assesses the Regulation's implementation since 2018, focusing on effectiveness, efficiency, relevance, coherence, and EU added value. The research, led by ICF and partners, employed mixed methods, including desk research, stakeholder consultations, and case studies across seven Member States. Findings indicate that while the Regulation improved planning and reporting quality, it did not ensure timely submission of National Energy and Climate Plans (NECPs) and Long-term Strategies (LTSs). The quality of reported information has improved, but inconsistencies and gaps remain, particularly in the completeness of NECPs and LTSs. The Regulation has partially streamlined planning and reporting processes but has not achieved full harmonization with other EU and international obligations. The Regulation's direct impact on stimulating spending and investment is unclear, and regional cooperation could be further encouraged. Multi-level and multi-stakeholder dialogues have not always been effectively established. The Regulation's compliance mechanism, largely based on non-binding recommendations, has not always sufficiently ensured implementation. Overall, the Regulation has added value by enhancing the consistency of national energy and climate policies and their planning. However, it faces challenges in ensuring accountability, addressing socio-economic issues, and aligning with recent legislative developments and global crises.