Every type of agricultural production is a burden for the natural environment. The paper’s objective is to assess the energy use efficiency, GHG emissions, and provide an economic analysis of buckwheat production for Central Europe (Poland). The analysis and comparison involved two production systems: low-input and high-input ones. The experiment involved three varieties of buckwheat, Panda, Volma, and Mancan. The yields for analysis were obtained from the field experiment which was set up in 3k-p fractional design was applied in two replications in which at the same time five factors were tested (A—variety, B—mineral fertilisation, C—sowing rate, D—weed control, E—growth regulator). A quartile was used as a statistical tool to select production systems. A high-input buckwheat production regime required, on average, 74.00% more energy than a low-input system. The total mean energy input for three varieties ranged from 7532.7 to 13,106.9 MJ ha−1 for low- and high-input systems, respectively. The results show that the energy use efficiency, specific energy, and net energy gain for the low-input system were on average 1.51, 9.6 MJ kg−1, and 3878.8 MJ ha−1, respectively, for the investigated varieties. For the high-input system, it was 1.35, 10.9 MJ kg−1, 4529.9 MJ ha−1, respectively. The total CO2 equivalent emissions during buckwheat production were higher for the high-input system than for the low-input system by more than 40%. The economic analysis demonstrated that the high-input system had better economic efficiency (without EU payment), 1.01 on average, than the low-input system, 1.07 on average. The international literature does not offer research on energy analysis for the production of common buckwheat and GHG emissions. The findings of this study demonstrate how the production systems affect energy and economic efficiency as well as GHG emissions. The authors suggest further research in Europe and globally, particularly on the energy use efficiency and GHG emissions in the production of common buckwheat, to verify the present results and improve production technologies (reduce inputs and costs).