Below is one of my contributions to the March issue of tED Magazine. Reprinted with permission.
Retrofits of fluorescent luminaires using tubular LED (TLED) lamps is growing in popularity, as evidenced by a recent U.S. Department of Energy (DOE) CALiPER report. The report reveals that TLEDs now comprise more than 10 percent of all listed products and 50 percent of all listed lamps in DOE’s Lighting Facts LED product database. More than 4,500 products.
There are several types of TLED lamps, including UL Type A, B and C in addition to hybrid approaches. Type A lamps are plug-and-play lamps that operate directly on a fluorescent ballast. Type B lamps feature an integral driver. Type C lamps feature an external driver.
TLED lamps offer the highest mean efficacy of any lamp type in the Lighting Facts database of LED products. Product performance varies, but about 90 percent of the listed TLED products have an efficacy topping 100 lumens/W, which is about the same as a bare fluorescent lamp. It’s also the minimum required to qualify for the DesignLights Consortium’s Qualified Products List, which many utilities use to qualify products for their LED rebate programs.
More than 100 products have an efficacy exceeding 150 lumen/W, including one operating at a very high 190 lumens/W. On average, TLED efficacy decreases by 3 lumens/W for every 1000K decrease in correlated color temperature. The average efficacy of a plug-and-play TLED is 113 lumens/W, TLED with an internal driver is 116 lumens/W, and TLED with an external driver is 115 lumens/W.
The Lighting Facts data reveals TLED lamps have higher efficacies than dedicated LED troffers. However, that is bare-lamp efficacy. LED troffers have greater efficacy than TLED lamps installed in fluorescent troffers. This is because of the effect of luminaire efficiency, or percentage of light exiting the luminaire. CALiPER data suggests luminaire efficiency for troffers with TLEDs installed is about 75-85 percent, which reduces efficacy for the installed solution.
The Lighting Facts data indicates TLEDs overall have somewhat higher efficacies, draw less power and emit fewer lumens than the fluorescent lamps they replace. The economic appeal is in the reduction in power that translates to cost savings. TLED lamps produce less light than their fluorescent counterparts do; the mean output of listed 4-ft. TLED lamps is about 2,100 lumens, less than a typical 4-ft. linear fluorescent lamp. However, the TLED’s directional light output improves luminaire efficiency. In some cases, this balances out to an equivalent luminaire light output; in others, a reduction in light levels must be acceptable.
Otherwise, color and power quality characteristics are fairly consistent across products, with color rendering index (CRI) in the low 80s; a choice of 3000K, 4000K or 5000K correlated color temperature; and power factor exceeding 0.90.
TLED lamps offer higher efficacy and potentially lower installed cost than LED retrofit kits and luminaires. However, when considering TLED lamps, tradeoffs such as luminaire efficiency, light levels, light level uniformity, aesthetics, ballast efficiency and remaining life (in the case of plug-and-play TLED lamps), and electrical/safety factors should be considered prior to commitment.
Download the report here.