Exploitation of energy crops irrigated with non-conventional water resources on a large scale could decrease negative impacts from fossil fuel use, at the same time saving potable supplies and reducing disposal of polluting effluents in surface water, particularly in environments with water scarcity as Mediterranean basin. To this end, three energy crops (Typha latifolia, Arundo donax and Phragmites australis) were planted in experimental plots and irrigated over a 2-year period with the effluents of an urban wastewater depuration plant. In general, treatment with wastewater increased the biomass yield because of the fertilising value of the wastewater and the soil chemical and physical of the soil structure is not threatened when compared to irrigation with conventional water. Heating values were higher for T. latifolia; nevertheless, the higher biomass productivity of A. donax makes the energy yield per unit of cultivated surface much higher than those of T. latifolia and P. australis. Even though the results achieved require further verification by mid- or long-term research, the present investigation shows that herbaceous crops irrigated with wastewater can produce appreciable biomass and energy yields. This is also an environmentally and economically sound way of wastewater disposal.