Volts vs Watts. Volts is the unit of measurement for potential difference while watts is the unit of measurement for power. These two are used only in electric circuits to quantify the power of a power source or the electricity needs of a certain device..Volts is the unit of measurement for potential difference while Watts is a unit of measurement for power. 2.You can get wattage by multiplying the voltage with the maximum current the power source can deliver.