Are you sure you mean volts and not watts?
If you mean voltage, you don't really need too worry. The PSU will always be able to provide enough volts.
If you mean watts, that depends on the parts. Usually you can find the amount of watts the component will comsume in the specifications of the parts. Write down how much power each component consumes, sum those numbers up and make sure your power supply can provide more power than all components consume.