Volt Equals Joule Per Coulomb. A watt is a unit of electrical power, which expresses how much energy (measured in joules) gets used or transmitted per second. This unit is a convenient.
The energy per electron is very small in macroscopic situations like that in the previous example—a tiny fraction of a joule. Voltage is a measure of electrical potential energy in units of volts or joules per coulomb (energy/charge).