Potential conductivity enhancement due to formation of space charge layers in nanoionic composites was computed numerically for several structures of non-conducting nanoparticles in a bulk ionic conductor. Optimum loading fractions were extracted from simulation results and found to depend strongly on the thickness of the space charge layer relative to the size of the particles. This behavior agreed well with an approximate analytical expression derived herein. In certain cases, significant conductivity enhancement was predicted, even for nanoparticle loadings as small as 0.5 volume %. The model was also applied to a space charge layer depletion scenario, and found to be in good agreement with results from a recent experimental study. (C) 2011 Elsevier Ltd. All rights reserved.