Abstract This work studied the potential use of the waste from Eucalyptus globulus and Eucalyptus nitens as energy crops, evaluating young and adult stages of both in all four seasons of the year with different moisture contents. The study was carried out made in Cantabria (North coast of Spain), located at latitude 43°28′N, and longitude 3°48′W. In this region, 29,513 ha are dedicated to the growth of Eucalyptus , with about 80% E. globulus , and 20% E. nitens . Six different plantations have been analyzed and their bioclimatic diagrams determined. After the collection of samples the potential energy of every sample was obtained, they were weighed, analyzed and burned, giving a mean net calorific value of 17,384 and 17,927 kJ/kg in the adult stage of E. globulus and E. nitens , respectively. The results for the young stage of both species were 17,708 and 18,670 kJ/kg. Moisture content in the samples has a great influence on power production. Finally, the economic and environmental consequences of these crop species for the region of Cantabria were analyzed.