The electrosurgical systems and methods of the present disclosure monitor power dosage delivered to tissue being treated with improved speed and accuracy. The electrosurgical systems include an output stage, sensors, analog all-pass filters, an analog multiplier, an average power calculation circuit, and a controller. The output stage generates electrosurgical energy to treat tissue. The plurality of sensors sense voltage and current waveforms of the generated electrosurgical energy. The plurality of analog all-pass filters filter the sensed voltage and current waveforms. The plurality of analog all-pass filter may have lagging or leading phase. The analog multiplier multiplies the filtered voltage and current waveforms to obtain a real power waveform. The average power calculation circuit calculates a real average power based on the real power waveform. The controller then generates a control signal to control the output stage based on the real average power.