HPAC Engineering, Oct. 2016, by Khalil Kairouz.
http://hpac.com/iaq-ventilation/fan-selections-and-their-energy-impacts-part-2-2

"Fans and fan systems can be significant consumers of energy in commercial applications and the greatest consumer in industrial ones. Concerned about underperformance, designers tend to compensate for uncertainties by adding capacity to fans. Oversizing fan systems creates problems that can increase costs and decrease reliability. This article explains how to evaluate fans and fan systems and their impact on operating costs."