More and more organizations are coming around to the idea that Data centers present good opportunity to reduce energy cost. Data centers have more than 10 million computer servers which on average consumes 15 times more energy per sq foot.

Association To Save Energy has good set of policies and recommendations for migrating to energy efficient data centers -

Data centers and their energy usage are expected to grow:

• The number of installed servers in the U.S. is expected to increase by 40 to 50 percent nationally in the next four years, with sales of new servers numbering about 7 million per year.
• Data centers in the United States now consume an estimated 20 to 30 billion kilowatt hours of electricity annually, roughly equal to the electricity consumption of Utah, or about 30 power plants.

Technical energy-efficiency opportunities that already exist:

• Use of the most current energy-efficient server processors
  • Most processors are 35 to 150 percent more efficient than previous generations.
• Management of applications to reduce computational power.
  • Software engineered to maximize energy efficiency would decrease unnecessary data center energy use.
• Improved efficiency of power supply and power distribution
  • Uninterrupted power supply systems are currently available with efficiencies as high as 95 percent – some current power supplies can have efficiencies as low as 60 percent.
• Right-sizing of cooling requirements
  • There is a tendency to overcool data centers.
  • Data center operators should be educated about proper air-cooling techniques.
  • Chilled water systems require only about 70 percent of the system wattage used by traditional air-cooled systems.
  • Cost may be a challenge for small- and mid-sized data centers.

Barriers to improved efficiency and change:

• Lack of real-world efficiency reporting from manufacturers on server components.
• Lack of energy-efficiency enabling requirements in software.
• The high energy costs associated with data center operation often are not addressed, because they represent a relatively small portion of overall data center operating costs.
• Incentives are needed for data center managers to make energy efficiency a priority.

Policy and design recommendations:

• Government should support efforts to develop metrics for servers and work toward establishing more reliable procurement standards.
• Governments should ensure that data center best practices are included in commercial building codes.
• Rebates should be offered to manufacturers of server components that meet efficiency standards such as 80plus®.
• Governments should encourage sub-metering of data center electricity use.

Check this pdf file for full report.