This paper considers energy as a basic resource which together with capital and labor contributes to output creation. It aims to explore whether European Union (EU) regions use these production factors in an efficient way as well as to assess the impact of various environmental variables on technical and energy efficiency. To that end, a two-stage analysis was conducted for the period 2005-2013. The first stage included an estimation of pure technical and total factor energy efficiency (TFEE) scores using the data envelopment analysis (DEA) methodology, while the second one included an exploration of the factors affecting efficiency scores obtained in the first stage by using random-effects panel Tobit regression. The results of DEA show that regional differences in technical and energy efficiency are considerable, whereby most of EU regions failed to utilize efficiently all of their resources. More developed EU regions are more technically and energy efficient. Moreover, most of EU regions experienced deterioration in TFEE in the recession years, The results of Tobit regression analysis, showing that there is a difference in the determinants of technical and energy efficiency, point out that human capital and innovation are particularly important for improving the region's efficiency or ecological performance. (C) 2018 Elsevier Ltd. All rights reserved.