Energy innovation is critical for addressing climate change and the ecological transitions of both developed and emerging economies. The present paper aims at the identification and assessment of patterns in energy innovation convergence across a sample of 27 European countries over the period 2000–2018. The research is based on data covering a broad category of patents related to climate change mitigation technologies in the energy sector, including combustion inventions with mitigation potential (e.g., using biomass), extracted from the Organisation for Economic Co-operation and Development (OECD) Statistical Database. Using a nonlinear time-varying factor model, the paper demonstrates that energy innovation efforts in the examined sample follow a pattern of club convergence. The findings allow the identification of three convergence clubs characterised by distinct disparities in energy patent intensity, as measured by the number of patent applications per 10 million inhabitants. Moreover, the results of an ordered logit model demonstrate that the emergence of the identified convergence clubs might be attributable to initial differences in per capita environmental research and development (R&D) expenditure, human resources in science and technology (HRST), and environmental policy stringency. The findings have important policy implications as they suggest the need for more tailored policies based on smart development and specialization frameworks designed to boost the energy innovation performance of the laggard countries, more fully exploiting the potential of their less technologically advanced sectors, such as agriculture.