In the last decades, a new phenomenon has arisen in connection with temporary or permanent non-use of land for agricultural activity, namely the cultivation of energy crops in these localities, because of growing demand for biomass as a fuel. Farmers are expected to sell energy crops and the fuels they produce, both at home and in the surrounding countries. To choose economically efficient energy crop species to cultivate, the thermochemical parameters of the crop should be used to support decision-making process of farmers. This paper summarizes the results of small-scale laboratory tests of three energy crop species planted in Slovakia – Sida hermaphrodita, Arundo donax, and Miscanthus × giganteus – used for determination of thermal and chemical properties of the energy crop species to evaluate their suitability for energy purposes. The most suitable species for energy purposes was found to be Miscanthus × giganteus with higher heating value of 19.6 MJ/kg, lower heating value of 14.8 MJ/kg (at moisture content of 17%), and ash mass of 2.67% dry mass (d.m.). From a lignin mass and activation energy point of view, the most suitable for energy purposes was Arundo donax, with a lignin mass of 20.5% d.m. and an activation energy of 124.2 KJ/mol.