Data centers have been a growth business in the United States in recent years. In 2006, U.S. servers and data centers consumed 61 billion kWh of electricity with a $4.5 billion bill, representing 1.5% of total electricity consumed in the U.S. that year, and a growth of more than 100% since 2000. Improving energy efficiency at data centers has apparent benefits to institutions and enterprises with large data centers. On the back of the rapidly growing information technology sector in China, data centers are being built out rapidly in the country. Against the backdrop of energy resource scarcity and strong government push for energy conservation and emissions reduction at the national level, energy efficiency and carbon dioxide emissions reduction by data centers commands great public attention.