No.

Most desktops (average video card, one/two hard drives, etc..) run in steady state at perhaps 140W or so, and that's what the PSU draws.

There are PSU differences, though. Any new PSU should really have at least an 80% efficiency rating -- check it before you buy.

The real trick is finding a PSU that is 80+% efficient in the typical 140-200W range. Having a 750W PSU that is 80% efficient at 600W is useless, and is also quite typical of such over-spec'd units.

Another trick the makers/sellers use, is to publish efficiency ratings that are only valid when run on 220-240VAC, with no comparable numbers for 120VAC. (The higher the input voltage, the more efficient the PSU, to a degree).

Cheers