Electric potential is electric potential energy (EPE) per unit of charge. (The unit of energy is the joule and the unit of charge is the coulomb.) Electric potential tells what the electric potential energy of a charged object will be for every coulomb of charge it has, or how many joules of energy there will be per coulomb. The unit for electric potential, joule per coulomb, it is named the volt in memory of Alessandro Volta. One volt equals one joule per coulomb.