Author Declan McCullagh wrote two articles on Sun Microsystems' energy advantages:
Congress: Buy energy-efficient servers now
"Sun Microsystems, for instance, sells servers outfitted with a low-power "CoolThreads" microprocessor that uses less power than an average light bulb... Sun, Hewlett-Packard, IBM, Advanced Micro Devices, Dell and others have even created an association called The Green Grid to promote power efficiency."
Sun: Niagara sequel more power-efficient
"Sun Microsystems has been touting the efficiency of servers using its first-generation UltraSparc T1 "Niagara" processor, but it's promising greater gains with the chip's sequel."