Ultimately, if capacitance is a function of voltage as for File 2, all of these methods only give a single average capacitance value which does not accurately reflect the complete behaviour of the cell. This may lead to inflated capacitance values and overreporting of the performance of non-ideal devices. If Equation 1 is used to calculate capacitance for a non-ideal device, researchers should only calculate this over the voltage range where the capacitance is constant, and should clearly report this voltage range alongside the capacitance. It must be noted that several groups raised concerns about analysing the non- ideal profile of File 2 using ideal capacitive methods. It was suggested by three groups that, rather than capacitance, capacity is a more suitable electrochemical property for non-ideal devices due to the variation of capacitance with cell voltage . Indeed, the use of capacity, would be expected to give identical results for different researchers, and would remove the ambiguity and confusion seen in Figure . Furthermore, capacity can be calculated for all energy storage devices with a wide range of GCD curves, and thus is an appropriate performance metric to compare the performances of many energy storage devices. Therefore, we recommend calculating and reporting capacity for all supercapacitors, especially those displaying non-linear discharge curves. This is crucial for ensuring reliable reporting of performance from non-ideal devices. Capacity can be calculated using Equation below: