Goal. To carry out a comparative assessment of perennial grasses on the energy productivity of biomass and optimize harvesting times for the production of solid biofuels. Methods. Field, laboratory, mathematical and statistical, computational and comparative. Results. The results of researches on the selection of uncommon energy crops and optimization of terms of their mowing for production of solid types of biofuels in the conditions of the Right-Bank Forest-Steppe of Ukraine are given. The highest linear growth was characterized by the Jerusalem artichoke grassland of the 1st year of use. The diameter of the stem of energy crops was 2.8–16.8 mm. The largest diameter of the stem had stagger bushes, perennial mallow, and Jerusalem artichoke of the 1st year of use. The highest density and energy consumption of 1 m3 of dry unpressed wood was characterized by perennial mallow, Jerusalem artichoke, giant miscanthus, Transbaikalian stagger bush with parameters of 125–138 kg/m3 and 2–2.56 GJ, respectively. The terms of mowing crops during harvesting in the autumn period for the production of solid biofuels according to the dry matter content in biomass have been optimized. Conclusions. Of the perennial energy crops on dark gray soils, the most productive are: giant miscanthus, Silphium perfoliatum L., Weirich and Sakhalin stagger bushes, perennial mallow, Jerusalem artichoke of the 1st year of use with the parameters of 11.1–15.8 t/ha of dry weight, 194–281 GJ/ha of warm energy and 6–8.6 t/ha of equivalent fuel. Harvest maturity of the studied crops (except for fodder sorrel) for the production of solid biofuels occurs in the late autumn period (10.11). The most technological crops for the production of solid biofuels with the highest dry matter content (83–87%) in biomass that do not require drying are: perennial mallow, Weirich stagger bush and Lophanthus anisatus. And the least technological crops are Jerusalem artichoke and Silphium perfoliatum L. with a dry matter content of 52–60%.