Thats only on a highly powerful PC with loads of components, and even dual video cards and dual processors
The standard I'd say is about 450-500watt for a standard powerful system, and any more is over doing it, and even adding to heat levels since more is being wasted.
So it is actually good to check what your computer would need, and maybe giving it a bit more power, but not going over the top, to make sure no wastage is being made than normal.