An electrosurgical system includes an electrosurgical generator and an instrument (255) coupled to the electrosurgical generator. The electrosurgical generator includes an output stage configured to generate the electrosurgical energy at a plurality of radio frequencies, a plurality of sensors (240) configured to sense a voltage waveform and a current waveform of the electrosurgical energy and a controller (260) coupled to the output stage and the plurality of sensors. The instrument is configured to supply the electrosurgical energy to tissue. The controller of the electrosurgical generator is configured to calculate at least one parasitic parameter based on the electrosurgical energy at the plurality of frequencies and to control the output stage based on the at least one parasitic parameter.
