An economizer is a mechanical device used to reduce energy consumption. Economizers recycle energy produced within a system or leverage environmental temperature differences to achieve efficiency improvements.

Economizers are commonly used in data centers to complement or replace cooling devices like computer room air conditioners (CRACs) or chillers. Data center economizers generally have one or more sets of filters to catch particulates that might harm hardware. These filters are installed in the duct work connecting an outside environment to a data center. Outside air also must be monitored and conditioned for the appropriate humidity levels, between 40% and 55% relative humidity, according to ASHRAE.

There are two versions of the device used in data centers: air-side economizers and water-side economizers.

  • Airside economizers pull cooler outside air directly into a facility to prevent overheating.
  • Water-side economizers use cold air to cool an exterior water tower. The chilled water from the tower is then used in the air conditioners inside the data center instead of mechanically-chilled water, reducing energy costs. Water-side economizers often operate during nightime to take advantage of cooler ambient temperatures.

Economizers can save data center operators substantial operating costs. According to, economization has the potential to reduce the annual cost of a data center's energy consumption by more than 60 percent. Use of cooler external environmental temperatures to preserve hardware is an important component in sustainable green computing practices in general. Unfortunately, economizers are only useful for data centers located in cooler climates.

This was last updated in July 2008

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