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Circadian Standard Observer Calculator

The SOWatt rating takes into account light coming directly from the luminaire to the eye as well as light reflected from the room surfaces defined for the standard observer. The method also accounts for different luminaire types (ceiling, pendant, wall wash, desktop) and their typical mounting locations within the standard room.

Similar to how EPA fuel economy ratings help consumers purchase fuel efficient cars, SOWatt helps lighting designers compare luminaires for circadian effectiveness. For more information about the metric and calculation details the following publication is available

Rea M, Bierman A, Thayer A, Jarboe C, Figueiro M. Standard observer watts: Evaluating the efficiency of circadian-effective luminaires using a standard observer methodology. Lighting Research & Technology. 2023;0(0). doi:10.1177/14771535221145606