The motives that firms have for investing in energy efficiency have been widely analysed in the literature. Particularly, there is a huge literature on barriers to energy efficiency investment and adoption. This paper reviews the econometric analyses carried out in this field. The main objective is to provide a general overview of the state of the econometric literature on the barriers and drivers of energy efficiency. We examine the main features of these studies and particularly the results of the explanatory variables used. We have classified them into three groups, barriers, drivers and firm characteristics. The paper ends with some suggestions for further analysis in order to improve our knowledge of energy efficiency investment.