I think everyone should watch An Inconvenient Truth. I feel sick at the thought of 2000W PSUs in computers that would probably be left on overnight.
The number of 2kW PSUs burning away at full power around the whole, all year, will be miniscule in comparison to the number of offices with hundreds of 50W systems left idling away over the same period. A computer room next to my lab has 30 machines that never get switched off, ever[\i].