lammert - 6:18 pm on Jul 24, 2010 (gmt 0)
The 1U heaters are indeed one of the reasons for the current focus on energy consumption per server, but I wouldn't say it's only a Green IT buzz. Until a few years ago servers with a height of 4U or 5U were common in data centers. That would give an energy consumption of a few kW at most per rack. With the reduction to 1U and 2U per server, the number of servers per rack increased significantly, and racks consuming between 6kW and 8kW are no exception anymore.
Many older data centers are simply not able to cope with that extra energy consumption per rack. Rack space providers either have to increase prices for power hungry users, or they have to leave server slots empty to prevent overload.
Regarding the CPU part of the energy consumption of servers, HP provides an energy calculation tool for their current server range which predicts the power consumption based on the actual hardware components used and the estimated server load. For the X3430 model I mentioned in the OP, the estimated total energy consumption varies between 90 and 167 Watt, depending on the load. This is for a 1U system with maxed out RAM, harware RAID controller and four disks. For a more common system with only one or two disks and without a separate RAID board, the percentual influence of the CPU on the total power consumption will be even greater.