Hi Donald,

Thanks for your question concerning the efficacy of LED lighting versus traditional T8 fluorescent lighting.

You are absolutely spot on in your concern about the output of LED lights, measured in lumens, not being as bright as their fluorescent counterparts. In fact, the Department of Energy has been so concerned about LED manufacturer’s claims of energy efficiency that they published two fact sheets in April and May 2010 comparing LED T8 replacement lamps with traditional fluorescent T8 lamps. You can read those fact sheets here http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/t8_replacem... and here. http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/led-t8-flou...

First, let’s get some units defined for lighting measurement. Power input is measure in watts, while lighting output is measured in lumens. The actual light level (illuminance) is measured in footcandles. This is the actual amount of light reaching the work surface, measured by a light meter. Lastly, the amount of lighting output per input, that is lumens per watt, is called the efficacy.

It’s important to understand these terms, because when considering a lighting retrofit the first thing to look at is whether the current space is over illuminated. This is measured in footcandles, NOT lumens. The Illuminating Engineering Society (IES) has recommendations for light levels for specific tasks listed in its IES Lighting Handbook. It’s common to find that the existing space is over illuminated, and by simply providing lighting at the recommended IES levels can save quite a bit of energy.

Now when comparing LED T8 replacement lamps to traditional fluorescent T8 lamps, DOE has found that the efficacy (lumens per watt) of traditional fluorescent T8 lamps are higher than those of LEDs, while the installation and overall life cycle costs are much lower. According to their tests, the “median efficacy for LED T8s tested to date is 44 lumens per watt.” Traditional fluorescent T8s typically have an efficacy of about 65-70 lumens per watt. DOE goes on to say that “LEDs will have to become two to three times for efficacious than they are today” to provide an equivalent light while saving energy.

Therefore, my recommendation is that you first hire a lighting expert to analyze your space to determine the proper amount of luminance required in footcandles for the tasks to be performed in that space. Then if you feel the need to upgrade the current T8 lamps, I would look into a high performance T8 lamp or even a T5. They have higher efficacies and cost much less than LED replacement lamps. Also look at the ballasts. If the space has older magnetic ballasts, look at replacing them with newer electronic ballasts. Electronic ballasts are about 30% more efficient than their magnetic counterparts.

I do believe that there will be a time when LED lighting will become the norm, but at the moment it doesn’t appear to be the most cost effective or energy efficient option on the market.

I hope this information helps with your lighting retrofit decision! Good Luck!

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