LED lights cannot be analyzed and compared the same way that incandescent and other traditional artificial light sources are evaluated. A traditional light fixture might come with a wattage rating and a few other measurement criteria that tell a user how the LEDs will operate generally throughout its useful lifespan. LED lights also come with their own sets of evaluation criteria, but unlike traditional lighting that might fail in a sudden or binary on-off fashion, the performance of LED lights can degrade slowly over time.
A quality LED lighting manufacturers that stands behind its products will do more than just provide initial ratings. Those ratings are useful but they give no information on how and whether the LED will sustain its performance characteristics over time. Lumen output testing is needed to complete the full slate of information that an LED consumer needs in order to compare products from different manufacturers according to a full set of objective standards.
Lumen Output Testing for LED Lights
The Illuminating Engineering Society of North America (IESNA) has developed two lumen output test standards that quality LED lighting manufacturers are using. The first standard, known as LM-80, measures an LED light’s lumen maintenance and depreciation over time. This standard simply compares the lumens that an LEDs generates when it is new to its lumen output at some specific future time. The test protocol includes temperature and other environmental characteristics to verify that LED lights are tested in standard conditions during each test.
Two LEDs that have identical initial lumen ratings, for example, can have dramatically different ratings after 30,000 hours of use. An LED lighting manufacturer whose products have been subjected to an LM-80 test, for example, might include a rating on the LED package stating that the light is rated at L80 after 30,000 hours, which means that the LEDs will continue to generate at least 80% of its initial lumen output at that usage point.
The second standard is a TM-21 test that extrapolates lumen maintenance information to tell the LED consumer how the lamp can be expected to perform after the LM-80 test specification. TM-21 extrapolations can give a consumer generally reliable information on how a light will perform between 30,000 and 60,000 hours. Both standards have their limitations, but an LED lighting manufacturer’s ability to provide this information allows consumers to compare different manufacturers on a more objective basis.
Read Between the Lines on Lumen Testing
Ultimately, both of these tests are measures of the durability of the LED lighting manufacturer’s products. LEDs from one manufacturer might have a lower price than a light from another manufacturer, even where both fixtures have similar initial ratings. The less expensive light, however, might not have good thermal control technology, and heat buildup in that fixture over time will reduce its lumen output more quickly than the more expensive lamp that does have good thermal control characteristics. The results of standardized lumen output testing on both lights will reveal their differences and will better explain the price differential.