The establishment of perennial crops has emerged as a very viable option for biomass-based energy production mainly due to their comparative ecological advantages over annual energy crops. This study is based on data collected from a field trial between 2002 and 2012 and was carried out with the main objective of evaluating the yield and quality performance of miscanthus and switchgrass using different harvest dates and N fertilization regimes (0 kg, 40 kg, 80 kg). Over the whole plantation period (including three years of establishment period), the mean yield of miscanthus was 16.2 t DM ha(-1) a(-1), while switchgrass yielded 10.2 t DM ha(-1) a(-1). In miscanthus, each increase in fertilizer level increased the N content in the harvested biomass, whereas in switchgrass, no significant difference was recorded for 0 kg and 40 kg N levels. The effect of N fertilization on ash was significant but independent of the crop. Both miscanthus and switchgrass biomass samples from the late harvests had a significantly lower N content than those from the early harvests. A Life Cycle Assessment covering the conducted field work and inputs of this trial showed relatively low energy input and emissions connected to the cropping of miscanthus. (C) 2015 Elsevier Ltd. All rights reserved.