Specific Fan Power (SFP) is a measure of the efficiency with which a given volume of air can be moved. Specifications often stipulate the allowable limit for SFP.
The SFP can be used to refer to the total power demand for paired supply and extract fans, or it may refer to individual fans.
For combined supply and extract units with heat recovery, the SFP is the total amount of electrical power supplied to fans, actuators and controls divided by the larger of supply or extract air flow rates at design load conditions. SFP for such units is typically expressed in watts of power per litre of air per second (W/l/s). AirMaster units use low noise, electronically commutated (EC) fans with a specific fan power (SFP) of just 0.7-1.2 W/l/s.