In this contribution we estimate supercapacitor impedance from temporal measurements from two points of view: i) fitting a predefined model to the temporal data and ii) transform time domain analysis to frequency domain to obtain a generalized impedance. A comparison between both methods is provided. In the temporal analyses we started with an a priori model: data was fitted to a three-model parameter. In the frequency domain, we obtained the impedance after temporal data conversion without an initial model. Frequency approach is limited by supercapacitor noise. We concluded that the frequency domain approach is preferable, and shows good agreement with conventional impedance spectroscopy techniques.