Calculating In Situ Fan Energy Index

As part of its Efficient Fans program, the Northwest Energy Efficiency Alliance (NEEA) contracted with Cascade Energy to conduct this research to gain additional insights into how energy-efficient fan systems perform in practice by comparing design-point Fan Energy Index (FEI) values with in field (in situ) performance outcomes. FEI is a standardized, unitless, design point metric that represents the energy efficiency of a fan system at a specific operating point. It compares the electrical power input of a given fan system (including the fan, motor, and drive) to that of a baseline, minimally compliant fan system operating under the same conditions.  

The report outlines the methodology for calculating the FEI of fans that are already installed and operating in situ. While FEI is traditionally calculated during the equipment selection process, it has also become a key metric for evaluating energy savings. Assessing in situ FEI can improve understanding of the real-world efficiency of fan systems, allow for comparison of actual performance to design expectations, and reduce uncertainty in energy savings measures that rely on this metric. By enabling more accurate assessments of fan system performance in the field, this work advances NEEA’s efforts to validate energy savings and accelerate the adoption of efficient fan technologies across the Northwest.