This paper presents an efficiency assessment of selected OECD countries using a
Slacks Based Model with undesirable or bad outputs (SBM-Undesirable). In this research,
SBM-Undesirable is used first in a two-stage approach to assess the relative efficiency of
OECD countries using the most frequent indicators adopted by the literature on energy
efficiency. Besides, in the second stage, GLMM-MCMC methods are combined with SBMUndesirable
results as part of an attempt to produce a model for energy performance with
effective predictive ability. The results reveal different impacts of contextual variables,
such as economic blocks and capital-labor ratio, on energy efficiency levels.