LED Myths, Part I

By Stan Walerczyk

Hopefully you already understand some very important facts about LEDs and LED products, but there are several myths that some distributors and contractors take as truth, when they are not.

This and the following column will state the seven total myths and provide a reality check.

MYTH 1 – L70 is the rated life of the LED product
L70 refers to when the LEDs still have 70% of initial lumens, which is considered end of rated life for LEDs, because they do not really die, they just get dimmer and dimmer. But L70 is not the rated life of LED products, because LEDs are usually not the weakest link. Drivers and especially their electrolytic capacitors, electrical connections, exterior lenses or housings, etc. will probably fail before LEDs reach L70. Warranty is probably more important than L70.

MYTH 2 – LED products last longer than all other high performance lighting products
This is related to the first myth. Even if the LEDs have a 100,000 hour L70, the driver or other components may die at 60,000, 70,000, 80,000 or 90,000 hours. Plus numerous LED products only have a 50,000-hour L70 rating for the LEDs. In non-air handling lensed troffers and other enclosed fixtures, I question if 50,000 hour rated TLEDs, also called LED T8s, will really last that long due to the heat. There are numerous extra long life fluorescent T8s, which are rated for up to 80,000 hours at 3-hour cycles and 90,000 hours at 12-hour cycles with program start ballasts. Electronic ballasts for T8 lamps are typically rated for 60,000 hours, but can last longer is kept cool and delamping can help them keep cooler. Not only can fluorescent lamps and ballasts last a long time, they cost less than LED products. Each extra long life fluorescent T8 may cost $4 – $5. Each high performance program start ballast may cost $15 – $25. There are also 50,000 hour rated ceramic metal halide lamps. Although induction lamps are rated for 100,000 hours, induction should not be considered, because of its bad efficiency and other reasons. You may find the following fluorescent lamp table of interest. If there any changes, that I am not aware of, please let me know.

MYTH 3 – Highest lumens per watt (LPW) is usually the best
For saving energy that is correct, but for cost effectiveness that is often not the case. LEDs are most efficient when under-driven from the driver. But for sufficient light, that requires additional LEDs, and as you all probably know too well extra LEDs increases product cost. There are some new extra efficient LEDs. Although these new extra efficient LEDs may not need to be under-driven, they can be quite more expensive than typical LEDs. For example a 3000 lumen 21W 140 LPW LED troffer or troffer kit may initially look better than a 3000-lumen 30W 100 LPW LED equivalent, but the 140 LPW version may cost $300, compared to $100 for the 100 LPW version. But based on $15/KWH and 3000 annual hours of operation, the 21W version would only save an additional $4.05 per year, so the payback compared to the 27W version would be 49 years, which is really infinite because it would probably not last that long. A good tool to use is lumens per initial cost.
3000 / $300 = 10 compared to 3000 / $150 = 20, and the 20 lumens per dollar is much better. If those numbers are relatively close together, the more efficient product may be better, because it will save more energy over the long haul, even if it costs more upfront.

If you have any thoughts on this column, please leave a comment below, or let me know at stan@lightingwizards.com.