A typical data center uses about as much energy for cooling as it does to power the servers. Some data centers however use significantly less. Google generally uses only about 20% of the cooling energy that a typical data center does.
The two biggest items that allow them to operate so efficiently are allowing a higher temperature, and using outdoor air for cooling. The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) has worked with the equipment manufacturers to determine what temperatures and humidity can be used. The current recommendation is for temperatures between 64 and 80 degrees Fahrenheit. The minimum humidity level has also been expanded and a minimum of 30% is allowable at the higher end of the temperature range. The maximum temperatures require an adjustment based on the elevation above sea level. The allowable maximum temperature for the most critical equipment is 89 degrees.
For operations that are classified less than mission critical, even wider temperature and humidity ranges allow outside air to be used without mechanical cooling or humidity control for many months of the year. Since this is the least energy intensive method of cooling significant energy savings can be realized.
Of course higher temperatures shorten the lifespan of the servers. On the other hand the cooler temperatures lengthen the life span. A study showed blade hardware server failures in the range of 2.5 to 3.8% over twelve months in two different data centers with supply temperatures of approximately 68⁰ F. In a similar data center that included an air-side economizer with temperatures occasionally ranging to 95⁰ F (at an elevation around 5200 feet) the failure rate was 4.5%. Failure in that study was defined as anytime a server required hardware attention. No attempt to categorize the failure mechanisms was made. In some areas of the country 95 degrees could be maintained without the use of any mechanical cooling which may make a 1% increase in the failure rate look attractive.
Since tape storage and printing operations have more stringent temperature and humidity control levels they should be separated from the rest of the data center.
Of course there are caveats. The wider temperature ranges are only for new equipment. At the lower humidity levels static electricity must be dealt with. Redundancy of the cooling equipment must be considered and noise levels in the room actually go up significantly as all the server fans speed up.
