A nonpolar capacitor is often used to compensate for reactive power in AC networks.
This property allows you to save up to 15% of the electricity meter. But to talk about 100% free electricity consumption is not taken into account it's stupid! Of course, not all that is shown in the video fact - the measurement of AC switch device can not be accurate and relevant.
Modern devices well record currents passing both on the line and on the zero wire and, although ways of bypassing new devices exist, this ROIC does not contain such information and is just an invention of the author and a joke!