Energy efficiency improvement (EEI) benefits the climate and matters for energy security. The potential emission and energy savings due to EEI may however not fully materialize due to the rebound effect. In this study, we measure the size of rebound effect for the two energy types fuel and electricity within the four most energy intensive sectors in Sweden – pulp and paper, basic iron and steel, chemical, and mining. We use a detailed firm-level panel data set for the period 2000-2008 and apply Stochastic Frontier Analysis (SFA) for measuring the rebound effect. We find that both fuel and electricity rebound effects do not fully offset the potential for energy and emission savings. Furthermore, we find CO2 intensity and fuel and electricity share as the two main determinants of rebound effect in Swedish heavy industry. Our results seems to imply that it matters both to what extent and where to promote EEI, as the rebound effect varies between sectors as well as between firms within sectors.