Nanofiber filters are typically fabricated using the electrospinning technique, which can reach high particle removal efficiency with relatively low air resistance because of the gas slip effect. They have a great potential for applications in the filtration units of heating, ventilation, and air-conditioning (HVAC) systems to reduce the fan energy consumption. This study systematically examined the relationship between pressure drop and face velocity for electrospun nanofiber filters. Experimental data of 122 nanofiber filters were collected from the literature to validate the theory regarding pressure drop for nanofiber filters proposed in previous studies. The linear regressions between pressure drop and face velocity showed that 89% of the tested nanofiber filters had an R-2 value greater than 0.9. Therefore, the pressure drop can be confidently regarded as being proportional to the face velocity for nanofiber filters. This conclusion was further confirmed by additional experimental measurements conducted in this study. After confirming the theory, the air resistance coefficients of nanofiber filters were calculated and compared with that of commercial HVAC filters. The comparison showed that the air resistances of nanofiber filters with careful design could be lower than that of the commercial filters with similar particle removal efficiency. (C) 2017 Elsevier B.V. All rights reserved.