If I use a 500W power supply when my PC uses about 170W will it use 170W of power or 500W?

[TheOkster]

If I want to buy a 500 watt power supply but my PC only uses 170W will it use 500W or ~170W?

 

[c4s2k3]

PC will draw whatever it actually needs, up to the maximum for the power supply. If your PC regularly draws 170w, it will be the same with a different PSU.