Energy intensity is one of the important and attractive indicators in energy economics. According to the abundance of energy resources in Iran, these resources are not used properly and therefore energy intensity is very high compared to other countries. Hence in this paper using a nonlinear regression method, we study the factors affecting energy intensity in Iran during the period 1979-2013. The results indicate that the existence of two regimes by considering relative price of energy as transition variable with the threshold about 1.58. The rate of urbanization and industrialization had positive effect and the level of technology and relative price of energy had negative effect on energy intensity in Iran. The effectiveness of relative price in the high price regime is intensified and the effectiveness of industrialization and technology is dropped. These results would suggest the important role of price regime on the effectiveness of energy intensity determinants in Iran and leads policy makers to prevent the decrease in the relative price of energy in the years following the implementation of targeted subsidies.