Evaluating LED Products
One of the best ways to evaluate an LED product is to determine what you will use it for. How you will use an LED lamp or light bulb is just as important as selecting the right product for the task needed. One way to evaluate an LED product is to determine the number of lumen output that the product offers.
However, lumen output is only part of the story and can be somewhat misleading.
To fully evaluate an LED product you may want to review the overall efficiency, optical control, thermal management of the LED itself, and know at what point in time the fixture will reach 30 percent lumen depreciation.
Lumen depreciation values reflect the overall performance of a lamp over its life.
As lamps are burned, their lumen output decreases. Most lamp manufacturers publish values for rated lumens and their “rated life”. In laymen’s terms, how long you plan to use your lamp per day will matter. An average consistent usage of 4 hours per day could mean that your LED product will last up to 10 years. Hence 30% depreciation would occur in the 3rd year.
Products with good optical efficiency and thermal management will be able to deliver more lumens on average, than traditional HID (High Intensity Discharge) products.
The Department of Energy concluded in its Solid-State Lighting Commercial Product Testing Program: "Until the field of SSL technologies and supporting knowledge matures, any claims regarding performance of SSL luminaires should be based on overall luminaire efficacy (i.e., from testing of the entire luminaire, including LEDs, drivers, heat sinks, optical lenses and housing), to avoid misleading buyers and causing long-term damage to the SSL market."
If you are choosing an LED for task lighting in an effort to support a hobby, such as quilting, model making or the like, you may want to choose a more highly rated product with sufficient lumen output.
LEDs used in decorative displays are often used at specific times of day and for very specific purposes, such as backlighting for an art object or in landscaping and therefore may enjoy a longer life as the percentage of usage is often minimal as compared to task lighting.