Typically, the “real” money in air-to-air energy recovery accrues from the first-cost “subsidy” (plant-capacity savings applied to the cost of the wheel) rather than lower operating costs. Still, if first-cost savings do not entirely offset the initial investment in the wheel, operating-cost savings may quickly make up the difference.

The interaction between wheel control modes and economizer operation justifies a detailed economic analysis using a tool such as TRACE® or DOE-2. Such an analysis can predict the length of the payback period based on building location, building type, HVAC system type, HVAC system control, and local utility rates.

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