the power supply does not draw 1000W all the time. it is capable of delivering 1000W if needed, it will only deliver whatever the PC needs. if your PC uses 449W at full peak then you will be using near 500W from the wall. if you have a 1000W PSU and only need 550Watts the units will be cool and quiet as it can deliver that with out breaking a sweat.
that is a very common misconception that total wattage equals all the time total draw.
assuming a 400W draw,, a 500W power supply and a 1000W power supply should draw the same power, the 1000 Gold will draw less power from the wall than a 650 bronze powering the same system.