LM Losses: Can You Handle the Truth?

Nicholson and Cruise II

While developing our LED Product Performance and Quality Ranking Report, I have encountered LED suppliers who have very different perspectives on providing LM loss data to buyers. Two examples remind me of the characters played by Tom Cruise and Jack Nicholson in the movie A Few Good Men. I thought the analogy would illustrate the importance of an informed buyer.

Is it fair to compare buyers and suppliers to the characters of Lieutenant Kaffee (I want the truth) and Colonel Jessup (you can’t handle the truth). Probably not, but I hope more buyers are like Lieutenant Kaffee and fewer suppliers view the world like Colonel Jessup.

The Backstory

Developing the LED Product Rankings requires persuasion – which is understandable, because we ask suppliers to provide data that requires testing by a third-party. It’s not unusual for a supplier to push back on some of our testing requirements. In the case of LM testing, it is my professional opinion that they are essential, but not everyone agrees. The following is a dramatization of discussions with two suppliers who have a different perspective on LM testing.

Conversation with Supplier A

Me: “Bill (not his real name), we would also like to get your LM79 and TM21 Ratings.”

LED Supplier Bill: “Marc, we are focused mostly on performance and have really great specs in that regard. We think that is most important to our customers.”

Me: “That’s great, and I would agree that performance is important, but so is quality and one measure we like to use are the LM ratings.”

LED Supplier Bill: “Well, we do have LM80 tests from the chip manufacturer, which as you know is one of the best in the world (I agree). We’re kind of new to the business and we haven’t tested LM79 or TM21 because we believe that the LM80 tests speak for themselves.”

Me: “Bill, LM80 tests are one indicator of quality, but what really matters to our members are fixture-level tests. As you know, OEMs make design decisions that can be very different from one-another, and they can result in big differences in LM loss rates.” (he agrees). 

LED Supplier Bill: “I’d really rather not spend the money if I don’t need to, but okay, I agree that they’re more valuable than LM80 tests alone and the quality of our design should hold up well under the scrutiny. Can you recommend a third-party that can test in a hurry?”

Before we were done with the call, I had introduced him to a third-party testing organization and he was busy getting quotes and making arrangements for a test (absolutely true). This is the kind of supplier that buyers like Lt. Kaffee should want to work with.

Conversation with Supplier B (Colonel Jessup)

Me: “Hi Colonel Jessup. Can I call you CJ?

LED Supplier CJ: No. Sir, will be fine.” (okay, that didn’t really happen)

Me: “Okay . . . uh Sir, we would also like to get your LM79 and TM21 Ratings.”

LED Supplier CJ: “Marc, the problem I have with LM ratings is they use lumens as the metric. It’s an erroneous measure that is bound to lead the buyer astray regarding making true performance comparisons. IES and DLC are working to define appropriate metrics for grow lights right now.”

I have some insight into the disagreements about LM testing (see Bob Erhardt’s comments at the bottom an earlier post). For the most part, they are related to testing the testing environment of horticulture lighting (i.e. temperatures), and have very little to do with lumens as a metric. LM losses are caused by flaws (called dislocations) in the materials that conduct electrons. These flaws reduce efficiency, and worsen with higher temperatures, drive current and age. High quality manufacturers have fewer dislocations. More importantly, a good power and thermal management design doesn’t accelerate their aging. Differences among chips and OEM designs are isolated and measurable at the fixture level, and it doesn’t matter whether they are measured in lumens or in photon flux.

Me: “Sir, there is no question that the semantics and interpretation of lumen maintenance losses is confusing for buyers of grow lights. Specifically, the nuanced differences in the PAR spectrum and color shift is not measured. However, LM loss rates are absolutely valuable (and necessary) to evaluate distinctions in the quality of the manufacturing process and materials of the chips themselves, and more importantly, the OEM design decisions on drive current and thermal management. We think buyers want to be informed.”

LM ratings may not be perfected for grow lights, but the are the best test of quality we have currently. I would disagree that they lead the buyer astray. In fact, they are more often ignored (or worse, misrepresented).  LM ratings ‘tease out’ lesser quality chips and shortcuts by OEMs. They serve as a flashing red light that something under the cover is wrong. It is our intention to drive this point home to our members in the form of educating them and demanding that OEMs disclose the specifications. The result will be a far better buyers’ decision making process and a more honest marketing culture”. 

Who do You Want as Your Supplier?

My harshest interpretation is that CJ doesn’t believe buyers are capable of understanding the nuances of LM testing and therefore it shouldn’t factor into their evaluation – lest they be led astray. In truth, I am probably being a bit unfair to CJ, but his reluctance to take the time to inform buyers for any reason (so long as the content is accurate) is counterintuitive for me.

In contrast, our first LED supplier – Bill – isn’t doubting the buyers capacity to understand. He believes in an informed buyer. I like Bill!

Can Buyers Handle the Truth?

I believe so, and am committed to the idea that more information, articulated in the right way, is always a good thing. What do you think? Please take the poll below, comment below, and share this blog with others. And register for our the First Edition of the LED Product Performance and Quality Ranking Report,


LED Lighting: TCO Part II – The Cost of the Lighting System

Breaking Down the Costs of Owning and LED Lighting System

TCO Graphic Part II

The Total Cost of Ownership is buried within the lighting system design, individual components, and manufacturing process. Some can be easily identified, while others are virtually impossible to discern without the manufacturer’s help.

PURCHASE PRICE: The LED Lighting Kit. A ‘kit’ is the complete set of individual components that make up the light system:

  1. The Fixture
  2. The Light Engine
  3. The LED Component
  4. Power Supply
  5. Power Cables

The Fixture can range from a simple extruded aluminum bar to a complex housing containing the heat sink, cooling fans, the electrical interface, power circuitry, power controls and control interfaces, sensors, and both light optics and protective lenses. In most instances (but not all), the fixture also holds the Light Engine. The entire fixture is priced (appropriately) as one unit. Fixtures have related installation and maintenance costs. Fans (active cooling) are more expensive to operate and maintain than a fixture that uses heat sinks only.

The Light Engine holds the LED components (or chips) that emit light. Light Engines are analogous to a bulb, but are typically integrated into the fixture (can’t be removed or replaced). High quality Light Engines are made of a metal-core printed circuit board (PCB) that holds the LED chips and makes the electrical connection between the incoming electrical current and the LED chips. The PCB boards are bonded to the heat sink to conduct heat away and maintain the operating temperature of the LED chips. Alternatively, individual LED chips with a metal substrate (often called a chip-on-board of COB) can attached individually to the heat sink with electrical connections made between each COB. The method of the connections vary widely in quality. Poor quality connections result in more frequent maintenance costs. Because Light Engines are integrated into the fixture, when they fail (and they do fail), the entire fixture must be replaced. The product warranty will pay for the replacement, but not the labor to monitor the lights, identify failures, remove the fixture, and replace it. An undetected Light Engine failure reduces crop production, as does the delay between replacements. Individual LED chip failures occur (much more often than the salesperson will tell you) and exasperate the problem. The higher the quality of the Light Engine, the fewer failures and the lower the maintenance costs. In most cases, the added cost of buying quality is worth it. We know of just one manufacturer who uses a replaceable Light Engine, which provides a number of advantages over an integrated Light Engine – the most obvious of which is avoiding replacing the entire fixture when a Light Engine fails. For all other systems, the Light Engine and Fixture are bound to each other, with the failure of any of the components causing the failure of the total system.

The LED Component (chip) deserves a separate discussion thread. They are the most important part of the entire lighting system, and vary widely in terms of performance and quality. There are only a dozen or so manufacturers of suitable LED chips (globally), and among these, there are only a handful that stand out in terms of performance and quality. Evaluating the quality of the epitaxy, bin, phosphor, and optics of the LED chips is beyond the scope of this article, however, there are two heuristic measures that summarize the differences; efficacy (performance) and L80 ratings (quality). Efficacy is the measure of light output to energy input, and has (by far) the largest economic impact on costs related to the lighting system. Further complicating the analysis is that efficacy is different for each spectra (color) of LED chip, requiring an efficacy calculation for the entire fixture. And the variance of fixture-level efficacy can be large – from less than 1.0 PPF/watt to 1.8 PPF/watt – a stunning difference, considering that the latter requires 80% less energy to produce the same amount of light. Our LED P/Q Rankings focus on fixture efficacy as the primary attribute of performance. The higher the efficacy, the lower your cost/lb of food will be. (note: we will discuss LED chip quality in a future article).

The Power Supply is typically separate from the Fixture and is almost always manufactured by a third party and priced separately. The Power Supply converts AC current to DC current (in most instances), and contains the circuitry for current control and dimming. These processes result in electrical losses of 8% to 15%, which you pay for in the form of electricity you have purchased (at the wall plug) but which is lost before it can power the Light Engine. The efficiency differences between Power Supplies is second only to LED chip efficacy as a cost consideration. The difference between a 15% loss and an 8% loss in significant in terms of your electrical costs. The efficacy measure of the LED P/Q Rankings encompasses a measure of the Power Supply efficiency, meaning it’s the best way to evaluate the energy costs of the entire system.

The Power Cable varies only slightly from one product to another, with the primary consideration being the distance (length) of the Power Cable between the Power Supply and the Fixture. All cables have ‘line’ losses that increase as the distance increases. When Power Supplies are located in close proximity to the fixture, these losses are trivial, but if Power Supplies are located away from the grow room, they can become meaningful.

Installation Costs. The cost of installing the fixture is almost always underestimated – and it can vary considerably from one product to another. Installing several light bars is more costly than installing a light panel that covers a greater area. More costly still is the cost of electrical wiring. AC connections require an electrician, so minimizing them reduces the installation costs. In general, you should plan for installation to add between 15% and 20% (in labor costs) to the initial purchase price of the light system (note: we will address thermal management, controls, sensors, optics and lenses needed for IP ratings in a separate article).

We noted earlier that identifying all of these costs without the help of the manufacturer is impossible. This is the main reason we work with manufacturers to aggregate the data and provide it in the form of the LED P/Q Rankings. We can’t emphasize enough how valuable we believe the Rankings are to you in your equipment evaluation.