There currently is a push to replace linear fluorescent T8 and T12 lamps with linear light-emitting diode (LED) replacement lamps, but are LEDs ready to take on this workhorse in general lighting? The evidence suggests no, not yet anyway, except perhaps in some specialty applications, such as refrigerated display cases.
Linear LED replacement lamps are designed to directly replace 4-ft. T8 and T12 lamps in existing light fixtures. A random sampling of products shows wattages ranging from 15W to 25W, availability in 2- and 4-ft. sizes, a selection of color temperatures from warm white (3,000K) to daylight (6,500K), and the ability to operate with or without the existing ballast. According to manufacturers, advantages include energy savings, long service life, suitability for cold-temperature applications, directional light, no mercury or lead, and resistance to shock/vibration.
Today’s white-light LEDs, for example, can produce up to 50,000 hours of service life with a few spot replacements. LEDs also produce light directionally instead of in all directions like a fluorescent tube, which can increase the efficiency of light fixtures into which they are installed.
But do LEDs provide sufficient value here? At $45–$300 per tube, they aren’t cheap. Suppose we have a two-lamp fixture with fluorescent T8 lamps powered by an electronic ballast, drawing 58W. The fixture operates 3,120 hours per year with a utility energy cost of 10 cents per kilowatt-hour (kWh). After replacing the two lamps with 25W LED lamps, we save 8W. The savings for this fixture are $2.50 per year. If the cost for each LED lamp is even as low as $45, the payback is 36 years. At $100, it is 80 years.
To sweeten the deal, we could include estimated lamp replacement and labor savings because of the maintenance benefit, but remember there are extended-life fluorescent lamps offering rated service life of 40,000 to 46,000 hours (at 3–12 hours per start on a programmed-start ballast), approaching the best that white-light LEDs can currently do. Additionally, many white-light LED devices actually produce less than 50,000 hours of useful life due to overdriving the LEDs to produce more light output.
But wait: What if the LED replacement lamps produce the same light output as fluorescent T8 lamps? And, what if fixture efficiency is improved—particularly if the existing fixture has inefficient reflectors, such as a common striplight with tagged-on reflectors? If these items are met, it may be possible to delamp, perhaps from three lamps to two, with a modest impact on light levels.
The biggest problem is that, at the time of writing, the U.S. Department of Energy (DOE) had published the results of testing of a series of 4-ft. LED lamps in a lensed troffer and a parabolic troffer as part of round 5 of its Commercially Available LED Product Evaluation and Reporting (CALiPER) program, and found manufacturers overstating product performance in terms of light output and efficacy. Although the directionality of LEDs did, in fact, improve overall fixture efficiency, none of the tested LED lamps turned out to be competitive with their baseline T8 and T12 rivals. And that’s not counting lumen depreciation over time, which is higher for LEDs than T8 lamps, and would be accelerated because of heat buildup in the LED devices.
The DOE report concluded, “In general, solid-state linear replacement products are not competitive in troffers as a replacement for linear fluorescent lamps at this time.”
Additionally, the DOE found that color temperature was frequently misstated, with two of the four tested LED replacement products found to have color temperatures well over 6,000K—one 7,739K and the other 12,583K—much “colder” than recommended.
Meanwhile, watch out for other misleading sales claims. One manufacturer, for example, claims a 10,000-hour service life for linear fluorescent lamps, which is untrue and creates an unfair comparison. This same manufacturer also claims an efficacy of 150 lumens per watt for LEDs, but this is for the LED device itself measured in ideal laboratory conditions, not the field and not for the complete replacement lamp.
There are four important lessons here: First, just because a lighting product is LED does not automatically mean it is efficient. Second, the best defense against misleading sales claims is knowledge. Third, trust sales claims for any lighting product only if they are backed by independent, reputable test results. And fourth, testing a retrofit lamp yourself in the intended application prior to purchasing is always a good idea.
In the end, LEDs really are just another light source and, as with all light sources, if they produce a benefit—in terms of either lower cost of operation, enhanced operational serviceability or lighting quality—that is equal to or greater than their cost, they are a good choice. If not, you are taking a risk.
To see the results of round 5 of the CALiPER testing, visit www.netl.doe.gov/ssl/comm_testing.htm.
Thanks to Stan Walerczyk, LC, principal of Lighting Wizards, and Kevin Willmorth, principal of Lumenique LLC, for their assistance.
DILOUIE, a lighting industry journalist, analyst and marketing consultant, is principal of ZING Communications. He can be reached at www.zinginc.com.