The paper reports the results of a research program aiming to evaluate the agronomic, and energy sustainability of the biomass production by perennial non-food herbaceous crops irrigated with different kinds of marginal waters. In four different sites (Bologna, Padova, Reggio Calabria, and Catania) the same four species (Arundo, Typha, Phragmites, and Lythrum), usually tested without irrigation, were planted and monitored during 2008–2010. The results show that a planting density of 10 m−2 is necessary to obtain a maximum dry yield levels already from the second year of transplanting. The maximum productivity was obtained with Arundo (close to 100 Mg ha−1 y−1 in Bologna and 86 Mg ha−1 y−1 in Padova, 50–60 Mg ha−1 y−1 in the southern locations). Lythrum productivity ranged from 5.2 to 9.2 Mg ha−1 y−1 in all the RUs, with the exception of Reggio Calabria. Typha (around 10 Mg ha−1 y−1 at the third year) and Phragmites (5–8 Mg ha−1 y−1) gave significant production only in the northern locations. The HHVs were close to 15.5 MJ kg−1 for Phragmites (except for Catania and Reggio Calabria with 20.0 MJ kg−1) 18.0 MJ kg−1 for the Arundo (except for Catania with 20.0 MJ kg−1), 18.5 MJ kg−1 for the Typha and Lythrum (except for Catania with 20.0 MJ kg−1).