Four dirty little LED secrets

Specify LED fixtures and create an unhappy client. Here’s what your mother never told you about LED lighting.

By Kenneth L. Lovorn, PE, Lovorn Engineering Assocs., Pittsburgh December 19, 2014

LED lighting has been presented to us as the savior for global warming, Al Gore, energy conservation, and anything else that might be remotely related to saving energy in our limited resource world. However, several caveats should be considered when deciding to install interior LED lighting. (These caveats do not, in general, apply to exterior lighting due to many factors that are outside the scope of this article.)

1. No matter what any sales literature says, if you have an LED fixture producing 80 lumens/W at the face of the fixture and a fluorescent fixture using a lamp that produces 100 lumens/W, the fixture with the greatest efficiency will be the one that saves the most energy. The calculation for the fluorescent must take into account the amount of light that does not leave the fixture, which could be 10% to 20%. That means the fluorescent fixture has a “face” output about the same as the LED fixture. Therefore, the only way for the LED to provide for a reduction in the lighting energy density would be to reduce the lighting level for the LED installation. Maintaining the same lighting level would result in no energy savings for either system.

2. The LED fixtures are significantly more costly than similar fluorescent light fixtures. A typical LED downlight can cost $200 to $400 per fixture while the same fluorescent downlight that will produce the identical lighting level costs $90 to $15, based on conversations with various lighting sales representatives. Therefore, to illuminate a room, the LED lighting installation will cost approximately twice as much, using the identical fixtures from the same manufacturer. The added cost of the LED fixtures will have a negative return on investment (ROI)—not only will they not pay for themselves, but they will have an increasing cost of ownership due to the significantly higher first cost because they are not as efficient as the equivalent fluorescent fixture. These costs are based on a nondimmed installation, because dimming for fluorescent fixtures is relatively expensive and will tip the balance closer to the LED installation for instances where the fixtures must be dimmable.

The secret life of the LED may be divided into two separate categories:

  • Older LED fixtures beginning with those at the inception of LED lighting and continuing into some time in the last year or so
  • LED fixtures that were introduced a year or more ago and extending into the present-day LED fixtures. We will treat these categories as separate entities because the resolution is different for each.

3. For the first, older category LED fixtures, the LEDs, drivers, heat sink, and supporting fixture hardware came as a complete unit, with no simple way to separate these components in the field. These fixtures had lives of 50,000 hours when they were installed (5 or so years burning full time, or double that for a typical office installation). At the end of their lives, the entire fixture must be replaced because the LEDs and driver board are integral with the heat sink. If these fixtures were installed in drywall or plaster ceilings, the ceilings must be removed to permit changing out the fixture.

4. For the newer fixtures, the LEDs and drivers were designed to be separable from the rest of the fixture so at the end of their life, both components would need to be replaced. Based on the operational times, this replacement would need to occur somewhere between 5 and 10 years so that the lighting levels could be maintained at or near the design levels. Failure to replace these components would result in significantly lower lighting levels in the space. While fluorescent lighting with a 30,000- to 36,000-hour lamp life would cost around $5 per lamp to replace, the LED and driver board cost between $120 and $250 per fixture, not including labor. Even if the fluorescent lamps were to be replaced twice for $20, the LED component replacement is significantly higher in cost for both the replacement parts and the labor to effect the replacement.

If you don’t want to have very unhappy clients, you should make sure that they recognize that the replacement costs for the LED and drivers can be considerable within a 5- to 10-year time frame. Also, if the LED components are not easily replaced, the retrofit process could be very disruptive to their operations, potentially requiring opening up the ceiling to access the LED components.

Kenneth L. Lovorn is president of Lovorn Engineering Assocs. He is a member of the Consulting-Specifying Engineer editorial advisory board.