Ablation performance indicator for electrosurgical devices is described where ablation is typically characterized by the generation of a plasma discharge at the electrode assembly of an electrosurgical probe. When the electrode begins firing, the current waveform assumes a distinct appearance characterized by a spike at the leading edge of each half cycle followed by a lower level for the remaining period of the half cycle. A calculation of the waveform's Crest Factor can be used to determine the state at the electrode, e.g., whether the ablative energy is causing a desirable ablative effect on the electrode. This provides real-time measurements of the RMS and peak current amplitudes along with the Crest Factor and may also be used as limits or inputs to control algorithms or as inputs to indicate whether the device is in its ablative or non-ablative state.