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Diminishing Returns: Still Save 50%, But 50% of What?

by Stan Walerczyk, HCLP, CLEP

With little low hanging fruit left cost effective lighting retrofits are becoming more of a challenge, if just hard savings, which include electrical savings, rebates and maybe also avoided maintenance savings, are included.

In the past going from four F34T12 fluorescent lamps and two energy saving magnetic ballasts, which consumed about 144W to two 32W F32T8 fluorescent lamps and a high BF electronic ballast, which consumes about 72W, saved 72W, which was 50% and was quite cost effective. We can now reduce wattage another 50% by going with 36W LED or high performance fluorescent systems, but only 36 watts are saved, so the electric bill reduction is only half of the previous retrofit. Based on 3500 annual hours and $.12/KWH electric rate, reducing wattage by 50% only saves $15.12 per year.

Hibays have a similar story. 1000W mercury vapor lamps with electronic ballast could be replaced one for one with 400W probe start MH lamps and magnetic ballasts very cost effectively. Later those 400W MH systems could be cost effectively replaced with 220W fluorescent T8 or T5HO lamps and electronic ballasts. But now it is a challenge replacing the fluorescent hibays with 110W LED hibays, because though the wattage is cut in half, only about 110 watts are saved. Based on 4000 annual hours and $.12/KWH electric rate, reducing wattage by 50% only saves $52.80 per year. Since LED hibays are relatively expensive and labor costs are usually quite substantial at these heights, $52.80 annual electrical savings is not that great.

Now, let’s look at screw-in omni-directional lamps, which do not started higher than 50% savings and now are less than that. A 60W incandescent bulb could be replaced with a 13W CFL, which was a 78% wattage reduction. Now that a 13W CFL can be replaced with a 9W LED, which is only a 31% wattage reduction. Based on being on 3000 annual hours at $.12/KWH electric rate, an LED will only save $1.44 in electricity per year compared to the CFL. 

Similar stories could be told about many other applications.

Extended life of LED products can reduce maintenance costs, but those maintenance savings may not be sufficient to get products approved. 

Plus now various energy codes may add cost to the project.

So distributors and contractors need to show customers that good lighting is much more than just a commodity and the ‘soft’ benefits of good lighting can dwarf electrical savings, rebates and maintenance costs. These soft benefits can include improved worker productivity, student test scores, retail sales, alertness, sleep, well-being, etc., which I have discussed in previous columns.

is principal of Lighting Wizards, an independent energy efficiency consulting firm. He has over 25 years of lighting experience including distribution, maintenance, retrofit contracting, and industry research. An Association of Energy Engineers-Certified Lighting Efficiency Professional, he also holds a Lighting Certified designation from the National Council on Qualifications for the Lighting Professions. He can be reached at stan@lightingwizards.com.

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