This study compares the biomass yield and energy efficiency of Virginia fanpetals grown in two production technologies (low- and high-input) during a long-term field experiment conducted in northeastern Poland. The analyzed crop was characterized by higher above-ground biomass yield and superior performance in the high-input relative to the low-input technology (5.1 vs 4.4 Mg ha(-1) y(-1) DM). Biomass yield increased until the third year of the experiment (9.1-9.8 Mg ha(-1) DM). Beginning from the third year of the study, the dry matter yield of Virginia fanpetals decreased by 2.1-23 Mg ha(-1) y(-1). In the first year of the experiment, the total energy inputs associated with biomass production in the high-input technology reached 122-128 GJ ha(-1). In the remaining years, energy inputs were determined at 11.2 (low-input) and 18.7 GJ ha(-1) y(-1) (high-input technology). Total annual energy outputs were determined at 75.5 (high-input) and 60.1 GJ ha(-1) (low-input technology). In north-eastern Poland, the energy output of Virginia fanpetals biomass was highest in the third year of the experiment (123.9-143.4 GJ ha(-1)). Beginning from the third year, energy outputs decreased by 30 GJ ha(-1) y(-1). During the 6-year experiment, the energy efficiency ratio of Virginia fanpetals was determined at 2.0-2.1. (C) 2019 Elsevier Ltd. All rights reserved.