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Saturday, July 30, 2011

Can LED lamps beat the products they replace?

Panelists at the US DOE SSL Workshop discussed a Caliper study on LED replacement lamps purchased at retail, which found the LED lamps generally did not meet the performance of the benchmark lamps.

At last week’s US DOE Solid-State Lighting Market Introduction Workshop in Seattle, WA (July 12-14), industry professionals considered whether LEDs can truly compete in the replacement lamp market. A summary report shows that LED replacement lamps purchased from different retail outlets between June and August 2010 often did not match the incumbent products they were designed to replace in terms of light output, color quality and lifetime expectations.

Retail lamp results

Samples of 33 LED replacement lamps, three units each, were first evaluated for light output, efficacy, power factor, chromaticity and color rendering. The lamps were then operated for 1000 hours and tested again. They were tested using the IES LM-79-08 standard (Electrical and Photometric Measurements of Solid-State Lighting Products). Measured product performance was compared with the manufacturer’s claims on the product packaging. The initial and 1000-hour test data sets were compared to provide an indication of the likelihood that products will meet their lifetime claims.

A range of types of SSL lamps were purchased that mimic conventional technologies in shape and size, including five A19, four B10 (candelabra), two C7 (night light), eleven MR16/PAR16, four PAR20, and seven PAR30. The authors of the report warn that this study represents only a sampling of the available replacement lamps and should not be used as a judgment of specific products, retailers or manufacturers.

Light output

Only a few of the products met or came close to meeting the average light output of the benchmark products. Two of the five A19 lamps came close to meeting the output levels of a 40W incandescent A19 lamp; four of the eleven SSL MR16/PAR16 lamps came close to meeting the light output levels of a 20W halogen MR16; none of the four PAR20 SSL lamps achieved the light output of a 35W halogen PAR20; and three of the seven SSL PAR30 lamps came close to meeting the light output levels of a 50W halogen PAR30 lamp.

Color quality
The 33 products had an average efficacy of 40 lm/W, with 13 products achieving greater than 45 lm/W efficacy. While all but two lamps met expectations for efficacy, several lamps had higher correlated color temperature (CCT) than indicated by the manufacturers, which could cause buyer dissatisfaction.

For instance, most products are marketed as replacements for incandescent products, implying a CCT of 2700-3000K. However, ten products had CCTs above 4000K. Thirteen products had CCTs above 3000K, perhaps making them a colder white than might be acceptable, while 16 were in the acceptable 3000K region. When all aspects of color quality were considered (CCT, CRI, and/or Duv), over half of the products had one or more unacceptable metric.

Fourteen of the 33 products had a power factor above 0.80. The other products had a range of power factors from 0.29 to 0.70.


The manufacturers’ claimed product lifetimes were in the range of 12,000 to 50,000 hours. After 1000 hours, three products operated at less than 70 percent of initial light output, while 12 other products exhibited less than 97 percent of initial light output. After 1000 hours, the remaining eighteen products exhibited between 97 and 100 percent of initial light output, with the greatest chance for meeting lifetime expectations. Notably, four of five Lighting Facts-labeled products performed at or near the original light-output levels after 1000 hours.

When lamp performance was grouped by retailer two retailers featured lamps with better performance overall, indicating that certain retailers may be implementing stricter screening procedures on the lamps they sell.

Rated performance

Packaging claims for most of the products included light output (lm), CCT and lifetime. The rated claims for light output and CCT were close for most of the products. However, when equivalency claims were provided (such as “5W = 40W light output”), they were inaccurate. The products did not provide the equivalent output.

The DOE suggests that consumers use data from the Lighting Facts label or LM-79 testing rather than manufacturer’s equivalency claims. They recommend improved education regarding color quality, light output, and the Lighting Facts and Energy Star programs to allow more informed purchasing decisions.

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