DC testing of electrochemical capacitors has been reviewed with emphasis on the test procedures used by the USABC, IEC, and the University of California-Davis (USA). Differences in the test procedures are identified and the effect of the differences on the inferred characteristics of various carbon/carbon and hybrid (pseudo-capacitive) electrochemical devices evaluated from test data. The effect of the test procedures is greater for hybrid devices than carbon/carbon capacitors. It was found that the differences in the test procedures have a minor effect on capacitance, but larger effects on resistance and energy density. The pulse power capability of devices is calculated from the rated voltage of the device and its measured resistance. The inferred power capability of a device based on the matched impedance value (V-2/4R) is nearly a factor of ten higher than that corresponding to an efficiency of 95% as required in the USABC and IEC test procedures. (C) 2010 Published by Elsevier Ltd.