Monthly Special Feature

Establishing LED Equivalency - An LED product package states “energy-saving 60-watt equivalent,” implying a direct one-for-one replacement for the common 60 W incandescent light bulb. Will it really produce the same quantity and quality of light? The checklist below summarizes key performance characteristics that should be considered when comparing LED products and evaluating their equivalency to conventional lighting technologies. No two products are identical in every respect, and tradeoffs are often necessary due to inherent differences in technologies. In fact, it may be possible to improve performance in one category, such as color rendition, while achieving equivalency in others. For any given application, a number of additional characteristics should be considered during product selection. Notable examples include sensitivity to heat in enclosed spaces, dimming capability and behavior, flicker, and power factor.

Characteristic Description - Light Output: Will the product appear equally bright? Equivalent products should produce the same light output, as measured in lumens. Wattage (input power) cannot be used to compare light output, even between two LED products.

Spatial Distribution of Light - Will the product direct or focus light in the same manner? Equivalent products should emit similar amounts of light in any given direction. That is, they should have a comparable luminous intensity distribution. It may also be important to consider the pattern created by the light, such as the sharpness of beam edges.

Color Quality and Appearance - What color light does the product emit? How do objects look under the light? An equivalent LED product should emit light that appears the same color (e.g., warm-white or cool-white) as the conventional light source, and any given object should appear the same color when illuminated by the light sources being compared. These attributes are typically characterized using the correlated color temperature (CCT) and color rendering index (CRI) metrics, respectively.

Form Factor - Is the product the same shape and size? A replacement lamp is of little use if it does not fit into an existing luminaire. Equivalent products should be within dimensional tolerances established by the American National Standards Institute (ANSI) for a variety of lamp types.

Compatibility - Will the new product work with my existing system? Different lighting technologies often require different accessory components. It is important to know if the product will perform as desired given the type of transformer, type of dimmer, and the connected load. Manufacturers should provide compatibility charts for their products.

Useful Lifetime - How long will the product last? Comparisons of rated useful lifetime are difficult because of the different rating methods used for LEDs and other light sources. Longer lifetime claims should be accompanied by longer warranty periods, and the product should continue to perform for the duration of the rated life.

Cost - Is the product worth the extra money? It is important to consider lifetime costs, not just the initial cost, because energy and maintenance savings can yield an attractive return on investment. LED products are typically more expensive on a first-cost basis, but prices continue to fall as performance improves. http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/establishing-led-equivalency.pdf