How to prevent overkill with a psu?

[Guest]

I don't know what this means could someone tell me just in case because I am buying a 700w psu?

 

[delluser1]

I don't know what this means could someone tell me just in case because I am buying a 700w psu?

A psu that provides much, much more wattage than your system requires.
Typically you want to be at around 50% use under load ( this is generally where a psu is considered most efficient ) but with modern psu's 20-30% up or down isn't going to make much of a difference.
Provide your system specs ( including psu make ) and someone will be able to tell you wether your intended psu is overkill.