the power draw depends on the usage of your components. the 500W is the rated max output of your psu (most likely will not give you this much output 
)
use something like psu calculator so you can get a rough idea about the power draw of your computer
https://outervision.com/power-supply-calculator

)use something like psu calculator so you can get a rough idea about the power draw of your computer
https://outervision.com/power-supply-calculator