Sewage sludge (SS) can be used in crop production to reduce the demand for non-renewable resources. The aim of this study, conducted in Poland (2008–2013), was to determine the influence of SS rates (0, 10, 20, 40, and 60 Mg ha−1 dry matter – DM) on the energy balance of cup plant biomass. In the first year, the energy inputs in biomass production ranged from 16.4 (without SS) to 31.9–102.7 GJ ha−1 (with SS), where root cuttings accounted for 59% (without SS) and 9–30% (with SS) of total energy inputs. In years 2–6, energy inputs were 7–18 (≤20 Mg ha−1 DM) and 16–40 times lower (≥40 Mg ha−1 DM). Dry matter yield ranged from 6.88 (year 1) to 7.03–19.50 Mg ha−1 y−1 (years 2–6). When applied at 10 Mg SS ha−1 DM increased dry matter yield by 36%, energy output by 43%, energy gain by 43%, and energy efficiency ratio by 25%, relative to the control. A further increase in the SS rate was not productive in terms of agronomic or energy efficiency. The application 10 Mg SS ha−1 DM optimized yields and the energy value of cup plant biomass.