© 2020 The AuthorsThe efficient use of energy contributes to less energy consumption and the reduction of greenhouse gases released to nature, thus improving environmental sustainability. For this reason, many countries pioneered by the developed nations are trying to develop policies for energy efficiency. In this context, the relationship between energy efficiency and greenhouse gas emissions was tested by panel co-integration, panel causality, and FMOLS and DOLS analysis. Given that the study used the datasets of 29 European countries over the period 1995–2016, there result suggests that there is a long-term relationship between energy efficiency and greenhouse gas emissions and that the quantity of greenhouse gas emission decreases as energy efficiency increases. Finally, the robustness and novelty by employing the Emirmahmutoglu & Kose (2011) Testing for Granger causality in heterogeneous mixed panels. Economic Modelling, 28(3), 870–876 approach, the findings illustrated that there is a causal relationship between energy efficiency and greenhouse gas emissions for many European countries. Overall, the current study presents a relevant policy direction for the European bloc countries. © 2020 The AuthorsEconomics; Energy; Environmental science; Statistics; Environmental analysis; Environmental pollution; Energy efficiency; Energy consumption; Greenhouse gas; Panel analysis; European countries.