How many volts is 500 watts?

The question is invalid.

Volts is a unit of electrical potential in fundamental units of joules per coulomb. Watts is a unit of (electrical) power in fundamental units of joules per second. As such, you can not determine volts from watts without knowing something else, such as amperes (coulombs per second) or ohms.

The conversion of Amps to Watts is governed by the equation Watts = Amps x Volts. For example 1 amp * 110 volts = 110 watts

You have two unknowns for this equation, 1) the voltage which you want to find, and 2) the amperage. You must know the amperage to find your answer. In household current the voltage is 110-120. However, if you use a car battery, the voltage is 12.

You could have the amperage and then use the equation above.

4 amps: 500watts = 4amps X ? volts. 500 watts/4amps = 125volts (close to household current)

42 amps: 500watts = 42amps X ?? volts. 500watts/42amps = 11.9volts prox. (close to a car battery)

1 amp: 500watts = 1amp X ??? volts. 500watts/1amp = 500volts (about like a large electric eel--300 to 800 volts)