Maximum Solar Heat Gain Factor is usually measured using the Btu (th) per Hour per Square Foot[BTU/h*ft²] for Heat Flux Density. Watt per Square Meter[BTU/h*ft²], Kilowatt per Square Meter[BTU/h*ft²], Watt per Square Centimeter[BTU/h*ft²] are the few other units in which Maximum Solar Heat Gain Factor can be measured.