The electrodes in solid oxide fuel cells (SOFCs) consist of three phases interconnected in three dimensions. The volume needed to describe quantitatively such microstructures depends on several lengths scales, which are functions of materials properties and fabrication methods. This work focuses on quantifying the volume needed to represent intermediate frequency heterogeneities in electrodes of a commercial SOFC using X-ray computed tomography (CT) over two different length scales. Electrode volumes of 150 m x 150 m x 9 m were extracted from a synchrotron-based micro-CT data set, with 1(3) m(3) voxels. 13.6 m x 19.8 m x 19.4 m of the cathode and 26.3 m x 24.8 m x 15.7 m of the anode were extracted from laboratory nano-CT data sets, both with 65(3) nm(3) voxels. After comparing the variation across sub-regions for the grayscale values from the micro-CT, and for the phase fractions and triple phase boundary densities from the nano-CT, it was found that the sub-region length scales needed to yield statistically similar average values were an order of magnitude larger than those expected to capture the high frequency heterogeneity related to the discrete nature of the three phases in electrodes. The challenge of quantifying such electrodes using available experimental methods is discussed.