Integrating natural resources and ecological services in the production process is crucial to implement sustainable agriculture. However, the measurement of natural resource efficiency remains difficult. This paper aims at contributing to this issue, by investigating French farms’ use and excess (slack) of energy resources through Data Envelopment Analyses (DEA). Results show that disentangling energy resources from the rest of intermediate consumption highlights energy use excess which is masked when considering intermediate consumption as a whole. The analysis of the determinants of energy use excess and of intermediate consumption shows a discrepancy in results, which policy-makers should take into account when designing energy policies. In addition, results show that large and highly capital intensive farms perform better in terms of energy use excess, while the dependence on public subsidies is a constraint.