Opteron More Energy Efficient Than Woodcrest?

While Intel has been touting the energy efficiency of their Core series of CPUs, there have been a few recent tests that suggest certain AMD CPUs might come out on top when compared with similar Intel CPUs.  The results of the latest test show a savings of nearly $100 a year:
“Specifically, the independent computer-testing firm announced today that it, in the tests, "the AMD based server used 7.3 to 15.2 percent less power at five different user load levels and 44.1 percent less power while the systems were idle and waiting for work."

That translates to annual electricity savings between $20.29 per server and $36.04 per server, depending on the workload, the study concluded. At idle speeds, it amounts to a $99.76 per-server, per year saving.” 
While this test and the others like it are showing some interesting results, this might just be the first round and nobody has scored a clear knockout just yet. 

AMD is gearing up to start selling their native quad-core technology, dubbed Barcelona, which is rumored to be more energy efficient than the Opterons of today.  Intel isn’t sitting idle in the area of efficiency either, so don't start calling the next round just yet.  Considering the massive leap in energy efficiency that Intel made when they moved from Netburst to Core designs, their upcoming "Penryn" chip family might be more evolutionary than revolutionary.  It will certainly be worth watching to see how Penryn does against Barcelona.