Question about power consumption...

[Whipsmack]

Say I have a 800 watt power supply and my computer really only needs 300 while in use.......only 300 watts will be used right? Or is there more power consumed just kinda hovering around in the PSU LOL...

Dumb question I know...but blah if I use anymore power my breaker is gonna start tripping. It usually in summer when I use an AC unit

 

[Bbq]

Yes, your psu only draws what it needs, minus efficiency losses.

Assuming you have a 75% efficient psu, and a 300w load from your parts. Your psu is only going to be drawing 400w, regardless if it's a 400w psu, or a 1.21 jiggawatt psu.