meV, keV, MeV, GeV, TeV and PeV redirect here. For other uses, see MEV, KEV, GEV, TEV and PEV. In physics, the electronvolt (symbol eV, also written electron volt) is a unit of energy equal to approximately 160 zeptojoules (10−21 joules, symbol zJ) or 6981160000000000000♠1.6×10−19 joules (symbol J).