it is due to the definition of voltage- Voltage is the difference in the electric potential between two points, and the electric potential is the amount of energy needed to move charged particle from infinity to particular place divided by charge of this particle.
Ivanthe terrible,
See the following Wikipedia definition, which shows a progression of definitions finally resulting in Newton-Meter/Farad. Multiplying by C gives newton-meter which is energy.
Regards,
Kral
Ivanthe terrible,
My previous reply was incorrect. It should have read Newton-Meter/Coulomb.
The Wikipedia use of the symbol "C" for charge instead of the usual symbol "Q" is a little confusing.
regards,
Kral