The cavity microelectrode (CME) technique was used to screen carbide-derived carbons (CDC) and carbon onions and investigate their electrochemical performance for electrical double-layer capacitors (EDLC) in an H2SO4 electrolyte. The results show that the CME is very effective in terms of screening large numbers of powder samples rapidly, reliably, and efficiently, compared with conventional based electrochemical techniques using large surface electrodes. The results obtained from CME for CDC agree well with the conventional technique. High rate response was obtained with carbon onions because of their high graphitization degree. Therefore, the CME technique could also differentiate microstructure variation in powder materials, especially under high scan rate (as high as 10V/s). These results show that, though the CME cannot completely replace conventional methods for electrochemical characterization of EDLCs, it is a complementary tool that can be used to quickly evaluate the performance of materials (combinatorial electrochemistry study) and highlight possible trends to explore using conventional techniques.