There’s been a race to the top among industrial LED lighting manufacturers as they scramble to squeeze the maximum possible lumens per watt (LPW) out of their products. With luminaires now topping 220 LPW, and individual LEDs capable of output in excess of 300 LPW, it’s become a major competitive differentiator.

The question is: for whom? As manufacturers promote their high LPW ratings, industrial customers are starting to buy into LPW as a standard of performance. But many customers don’t realize that in order to drive up LPW, manufacturers have to sacrifice overall fixture performance and longevity. For some manufacturers, it’s a distraction tactic-they’re using a bright, shiny thing (literally) to draw attention away from their overall performance deficits.

What good is a fixture with high LPW if it can’t withstand the rigors of an industrial environment or it burns up in three months? Manufacturers who compete on LPW are putting the cart before the horse: if the fixture is unreliable, uncomfortable for the eyes and prone to frequent failure, its high LPW is irrelevant.

Higher LPW = Diminishing Returns

The reality is that a higher LPW comes at a steep price, and manufacturers must sacrifice performance in five key areas:

  • Thermal management: A high lumen output is a key ingredient in LPW. In order to amplify lumen output while working within the same fixture size, fixture designers often resort to overdriving the individual LEDs by ratcheting up the amperage throughput. This not only detracts from fixture efficiency, but also increases heat output, causing the overall fixture to run hotter than normal. This can damage the LEDs and other system components, accelerating fixture failure. And, in areas where combustible materials are present, the excess heat produced could create a serious risk of explosion or fire.

  • Fixture size: An alternative to overdriving the LEDs is to add more LEDs, but underdrive them with lower amperage. This solves the energy efficiency problem but means a dramatic increase in the size and cost of the fixture. Now, you have a more efficient fixture, but it’s too large to fit in the available space and too expensive to buy and ship, making it impractical for most applications.

  • Optical control: In a bid to increase LPW, many manufacturers eliminate fixture lenses and/or reflectors that help to direct the light where it’s needed. The idea is to remove any obstruction to light emission to maximize lumen output. But this sacrifices optical control and creates an uncomfortable glare that causes visual discomfort. Not only is this bothersome to workers, but much of the light is also being wasted on the walls and other areas that don’t require illumination. In this case, a high LPW isn’t efficient at all.

  • Fixture life: By overdriving the fixtures, manufacturers are effectively shortening the useful life of the fixture. Simply put, higher lumens per watt is hardly an advantage when the light needs to be replaced three times as often. As a result, a high LPW only serves to diminish the customer’s return on investment.

  • Warranty: Fixtures with higher LPW will also carry a shorter warranty. Because they’ve sacrificed fixture life and reliability to drive up LPW, manufacturers are reluctant to offer extended performance warranties. This means that as LPW goes up, protection for the buyer goes down.

All of these sacrifices add up to an underperforming fixture that actually costs more to operate over the long haul, resulting in overall lower customer satisfaction throughout the life of the fixture. Between the risk of frequent replacement and the hassle of maintenance, it’s simply not worth it for an extra 5 LPW that only saves $0.20 per fixture in energy costs.

Consider the Whole Fixture as a System

Rather than buying into high LPW hype, buyers must consider industrial LEDs as a complete system, with multiple factors that play into the standard of performance in order to feel confident they’re buying a product that’s built to last. This industrial LED trifecta — cost, efficacy and light quality — are the true hallmarks of a high-performing fixture and make a far bigger impact on customer ROI and satisfaction.

  • Cost: Buyers must consider not only the initial cost to purchase the fixture, but also the total cost of ownership (TCO) over its lifespan. If fixture life is shortened by overdriving the LEDs, that means more frequent replacement, which adds to the overall TCO. The alternative — adding more LEDs and under-driving them - adds size and weight to the fixture, which increases purchase cost. The key is to strike a balance. In addition to energy savings, buyers must also consider the savings generated by reducing or eliminating lighting maintenance and choose lights that don’t cause more trouble than they’re worth.

  • Light efficacy: When designed with a proper optical lens, LED systems can direct light where it’s needed, reduce glare and even reduce the number of fixtures required to light the same space due to precise light placement. When the lens is left out to boost LPW, it results in glare, wasted light and thus, wasted energy. Instead of prioritizing a high LPW, look for a fixture with high enough LPW to qualify for DLC energy rebates, but not so high as to sacrifice the efficacy of the light itself.

  • Light quality: One of the key advantages of LED lighting is its superior color quality and near-daylight color rendering for better visual acuity. But LEDs with higher CCT (color temperature) and lower CRI are generally associated with highest efficacy. So, in order to boost efficacy, some manufacturers will amp up CCT, causing uncomfortable glare, and sacrifice CRI, which impacts color perception accuracy. Instead, choose a fixture that provides good visual acuity, accurate color rendering and one that reduces eye strain.

Look for a fixture with high enough LPW to qualify for DLC energy rebates, but not so high as to sacrifice the efficacy of the light itself. This can be especially important for public facilities like this wastewater treatment facility.

LPW: More Doesn’t Mean Better

While many manufacturers are basing their performance claims around a high LPW, there are numerous quality and performance factors that must be considered in the industrial LED purchase decision. In order to maximize the overall lifetime performance, ROI and satisfaction with industrial LED fixtures, buyers must look beyond the hype of high LPW and choose fixtures that provide the light quality, light efficacy, long-life performance and TCO that actually deliver on the promise of LED technology.

This article was written by Vishnu Shastry, Optical Engineering Manager, Dialight (Farmingdale, NJ). For more information, contact Mr. Shastry at This email address is being protected from spambots. You need JavaScript enabled to view it. or visit here .

Photonics & Imaging Technology Magazine

This article first appeared in the July, 2020 issue of Photonics & Imaging Technology Magazine.

Read more articles from this issue here.

Read more articles from the archives here.