Percolating networks of silicon nanowires, also called nanonets, have been proposed as a possible material for the channel of Field-Effect Transistors. Experimental results have shown that the dependence of current-voltage characteristics with parameters such as device dimension and nanowire density might be influenced by the statistical dispersion of individual nanowires threshold voltage. In order to further analyse this effect, this paper provides a finite element simulation of such nanonet-based field-effect transistor. We studied the influence on transistor characteristics of above-mentioned parameters. Simulation results were compared with experimental ones using the same parameter extraction methodology as in experiments.