Efficacy and Life Standards
The following will be used as a basis for stating performance of products on this blog:
Source Efficacy - Lumens per watt, or “Source L/W“, with operating temperature stated in degrees C (ex. 25C), does not include driver or power supply losses and is to be provided as reference only. At no time will this be represented as product applied efficacy for use in applications other than the inclusion in a product.
Luminaire Efficacy – Lumens per watt, or “Luminaire L/W“, to include ALL losses through the power supply, driver, controller, and optical system, with ambient operating temperature stated in degrees F (ex. 70F). Under no circumstances are luminaire efficacies to be stated without operating system and optical lossed included.
The DOE and NIST have established that the maximum efficacy of solid state sources is 230 lumens per watt at the die level. This is under optimal conditions, at 25C, in laboratory conditions, and at a CCT (color temperature) generally higher than is considered acceptable for general illumination. Warmer colors, device packaging, higher operating temperatures (both ambient and thermal junction), optical losses, power supply and driver losses will reduce this maximum capacity significantly. Practically, the maximum luminaire efficacy of a 3,500k luminaire, assuming 10% package source loss from raw LED die potential + 10% power supply losses + 15% loss from operation at a more realistic applied 35C operating temperature + 5% optical system loss = 167 lumen per watt ceiling for neutral white light producing luminaires (slightly less for warm white sources.) When these losses are applied to an LED die performance of Source 150 L/W, a maximum luminaire efficacy of Luminaire 98 L/W is realistic in the near term.
Based on the above, any claims of efficacy on this blog of 150 L/W at the source and 98 L/W for a luminaire will be scrutinized and subject to severe scrutiny. Except for special circumstances, Luminaire L/W can be expected to be between 72% and 80% of the source LED packaged source efficacy at 25C. In reverse, to find source device L/W, multiply Luminaire L/W by 1.38. For example, for a luminaire to generate 60 L/W, packaged LED source efficiency will be roughly 83 L/W. Any greater performance will be considered carefully and critically.
Rated Service Life – Per ASSIST, the rated service life of an LED product will be either to 70% or full light output for commerical products or 50% of full light output for residential products. Under no circumstances will rated life” without lumen loss qualifier be considered acceptable, as this can conceal severe lumen losses and poor performance.
Ideally, sources and luminaire products will be tested using the IES LM79 standards, and sources will have been tested using the IES LM80 standards for lumen maintenance. In the future, claims of products that have not been tested using these standards should be considered marketing hype.
