Calculating SSL Performance from LM-79 Photometry for a Related Product
The industry-standard test method for SSL products, IES LM-79-08, requires the use of absolute photometry. This enables equitable performance comparisons between products and against specifications, but can also result in very high testing costs for families of products because each and every possible variation of products within the family requires an individual test. In contrast, other common light source technologies (such as fluorescent and high intensity discharge) can use relative photometry, which allows calculation of photometric performance for a variety of products based on separate tests of lamps, ballasts, and luminaires.
Currently, many LED luminaires are not suitable for relative photometry because the LED light sources are generally not interchangeable and for other technical reasons. However, an increasing number of LED luminaire manufacturers have shown they can accurately calculate luminaire performance by extrapolating absolute testing results from one or more luminaires to a family of similar luminaires.
The LED lighting industry has progressed significantly in terms of accuracy of performance claims, as revealed in CALiPER testing over the years. In recognition of this progress and the continued rapid growth in product introductions, DOE will accept calculated performance data for product families listed by the LED Lighting Facts program. DOE is also implementing procedures and safeguards to maintain the high degree of accuracy in performance reporting for products listed on LED Lighting Facts, including an independent verification testing program and public reporting of verification testing results. This new system will allow LED Lighting Facts users to continue to rely on LED Lighting Facts as a resource for obtaining accurate product performance information, while allowing manufacturers to greatly reduce their testing costs.