Research and development (R&D) spending in the energy sector, which is aimed at exploring ways to reduce greenhouse gas emissions, among other things, plays a vital role in achieving the goal of climate neutrality. The purpose of this paper is to assess the environmental performance of R&D spending in the energy sector of selected EU member states from 2011–2017/2019, and to compare the results. Taxonomic research with the zero unitarization method was used, which enabled a synthetic assessment of EU countries according to the environmental performance of the total spending in the energy sector and an analysis of the changes in performance for six categories of spending in this area. The assessment of changes in the environmental performance of individual categories of R&D spending over time using the applied method was an added value compared with the assessment methods previously used in this area. The study found that there were significant differences in the level of environmental efficiency of R&D expenditures in the energy sector between countries, changes in environmental efficiency in most of the countries studied were not satisfactory, the most environmentally efficient expenditures were on renewable energy, other power and storage, hydro and fuel cell technologies, and the least on fossil fuels and nuclear energy. The results reflected both the member states’ progress towards climate neutrality and the discussion on the environmental performance of the means and directions of actions aimed at this