Which statement best describes the primary benefit of using an outside air economizer?

• A. It increases indoor air temperatures to improve comfort.
• B. It eliminates the need for any mechanical cooling.
• C. It reduces energy consumption by decreasing mechanical cooling requirements.
• D. It increases humidity indoors.

Answer: (C)

Outside air economizers work by using outdoor air to meet part of the cooling load when outdoor conditions are favorable, so the mechanical cooling system doesn’t have to run as much. That reduction in compressor and fan energy is the primary benefit, which is why the best statement is that it lowers energy consumption by decreasing the mechanical cooling requirements.

The other outcomes aren’t the main goal. Increasing indoor temperatures to boost comfort isn’t what economizers aim for, and they don’t guarantee a complete elimination of mechanical cooling—they typically reduce, not remove, the need for it. Humidity effects depend on outdoor conditions and aren’t the primary reason for using an economizer.