View source for Physics:Coefficient of utilization

{{Short description|Efficiency of luminaire in transferring light energy}}
A '''coefficient of utilization''' ('''CU''') is a measure of the efficiency of a luminaire in transferring [[Physics:Luminous energy|luminous energy]] to the working plane in a particular area. The CU is the ratio of [[Physics:Luminous flux|luminous flux]] from a luminaire incident upon a work plane to that emitted by the lamps within the luminaire.  As a ratio, the coefficient of utilization is unitless.

For example, some of the light emitted by a luminaire may exit away from the desired plane and is therefore wasted. A CU measures the light actually reaching the desired plane as a percentage of the total light produced by the fixture. The value for direct lighting varies from 0.2 to 0.5 while that of indirect lighting varies from 0.1 to 0.3

==See also==
*[[Physics:Luminous efficacy|Luminous efficacy]]
*[[Physics:Wall-plug efficiency|Wall-plug efficiency]]
{{DEFAULTSORT:Coefficient Of Utilization}}
[[Category:Photometry]]
[[Category:Lighting]]

{{Sourceattribution|Coefficient of utilization}}