Abstract The energy efficiency indices are not affected by market fluctuations and they are more stable in time and space. The use of mineral fertilizers is a major energy input element in crop production. Therefore, the aim of the study was to determine energy input, energy output, and energy efficiency indices in camelina and crambe biomass (seeds, oil, straw) production depending on rate of mineral nitrogen (N) fertilizer application (0, 60 and 120 kg ha−1 N). The dry camelina seed yield was significantly differentiated by fertilizer application, while no such relationship was found for crambe. The highest dry seed yield was reached for both species in the warmest 2018 year. The total energy input in crambe production on a plot with no N fertilizer application was 10.19 GJ ha−1. However, it increased with an increasing N rate to 13.25 and 16.30 GJ ha−1, for 60 and 120 kg ha−1, respectively. The energy gain from crambe production was the highest on the plot with no fertilizer application (80.9 GJ ha−1) and decreased with increasing fertilization rates (by 8% and 11%, for 60 and 120 kg ha−1 N, respectively). Camelina gave the highest energy gain (67.5 GJ ha−1) on the plot with rate 60 kg ha−1 N, and an increase in fertilization or its absence decreased this index by 6% and 3%, respectively. The average energy ratio for crambe seed production (3.9) was significantly higher (by 13%) compared to the average value for camelina. The application of N decreased the seed production energy ratio compared to the control plot with 0 kg ha−1 artificial N applied, both for camelina and crambe by 13–26%, and by 23–37%, respectively. Further research is needed to verify these findings and to address the issue of economic and environmental production efficiency of these two promising oilseed crops.