Exposing the truth behind manufacturers’ efficacy claims

 

 

LED technology has transformed the lighting industry. Compared to traditional lighting solutions like incandescent and fluorescent bulbs, LEDs are more energy-efficient, produce better light quality, and last longer—making them a popular choice across many industries. According to the U.S. Department of Energy, LEDs made up 48% of installed lighting units in 2020, compared to just 8% in 2015 and 1% in 2010.

 

As LED adoption continues to rise, so does the competition among manufacturers to create brighter and more efficient fixtures. One key metric used to describe this performance is “luminous efficacy,” which measures how effectively a light source converts electrical power into visible light. While it's an important indicator, it's also one that can be misleading if not properly understood.

 

Manufacturers often test only the bare LED chip rather than the complete fixture, including lenses and other components, to inflate their efficacy numbers. This practice makes it difficult for buyers to compare products accurately or understand the real-world performance of a system. In this article, we'll explain what luminous efficacy really means, why it matters for solar lighting, how some manufacturers misrepresent it, and how you can spot reliable products from those that don’t deliver on their claims.

 

What is Luminous Efficacy?

 

The Illuminating Engineering Society (IES) defines luminous efficacy as "the total emitted luminous flux divided by the total source electrical input power." It’s typically measured in lumens per watt (Lm/W) and indicates how efficiently a light source produces visible light. For example, a fixture that emits 1500 lumens using 20 watts would have an efficacy of 75 Lm/W. If another fixture produces 2500 lumens with the same 20 watts, its efficacy would be 125 Lm/W—clearly higher because it generates more light with the same amount of power.

 

 

Though efficacy is often confused with efficiency, they are different concepts. Efficacy refers to the amount of visible light produced relative to the power consumed, while efficiency relates to the proportion of light actually delivered by the fixture compared to what it’s capable of producing. Efficacy is the better metric for comparing fixtures, but it's crucial to recognize that the terms are not interchangeable.

 

Why Does It Matter for Solar Lighting?

 

Most lighting systems in the U.S. are grid-connected, making high-efficacy fixtures attractive because they provide more light for less energy. However, when it comes to solar lighting, where energy is free and abundant, the importance of efficacy might seem less clear. But here’s the thing: even with free energy, lower power consumption still matters.

 

A higher-efficacy fixture uses fewer watts to produce the same amount of light. This reduces the size and number of solar panels and batteries needed, resulting in a more cost-effective solution. It also allows for smaller mounting structures and makes solar lighting viable in high-latitude regions where sunlight is limited. In short, efficacy plays a critical role in the performance and affordability of solar lighting systems.

 

How Do Manufacturers Mislead With Efficacy?

 

Some manufacturers exaggerate their products’ efficacy by testing only the bare LED chip without considering the full fixture, such as lenses and drivers. This approach leads to inflated LPW values that aren’t reflective of real-world performance. The result? A product that looks great on paper but underperforms in the field.

 

This lack of transparency makes it hard for buyers to compare products fairly. To avoid being misled, it’s essential to look for independent testing, such as LM-79, which ensures accurate and standardized measurements of a complete lighting system.

 

The Importance of LM-79 Testing

 

LM-79 is a standardized test developed by the IES to measure the optical and electrical characteristics of solid-state lighting (SSL) products, including luminous flux, intensity, color, and efficacy. Unlike other tests that focus on components like LED chips, LM-79 is performed on the complete fixture, providing reliable and comparable data between manufacturers.

 

 

When evaluating a product, always check for LM-79 reports. These are available on manufacturer websites and provide a transparent view of the fixture’s true performance. Tier 1 manufacturers like Acuity and Cree typically conduct rigorous testing, making them more trustworthy than lesser-known brands.

 

Other Red Flags to Watch For

 

Beyond LM-79, there are other signs that a product may be overstating its efficacy. For example, if a fixture claims an efficacy of over 160 LPW, that should raise a red flag. Most reputable manufacturers stay within a range of 120–160 LPW depending on the performance package. Also, if a product maintains the same efficacy at different power levels, that’s a warning sign. Efficacy should decrease as power increases and increase as power decreases.

 

Making Informed Purchase Decisions

 

Understanding luminous efficacy is crucial when selecting lighting products, especially for solar applications. Not all manufacturers measure it the same way, and some may use misleading terminology. However, independent tests like LM-79 help standardize the process, allowing for fair comparisons between products.

 

If you can’t find clear information about a product’s efficacy, ask the manufacturer these questions:

• Can you provide independent testing results for your efficacy claims?
• How do you measure lumens in your products?
• What is the total fixture efficacy, including drivers and lenses?
• Do you provide photometric reports for your fixtures?
• Are your efficacy claims based on initial or maintained lumens?
• Can you share references or case studies of your fixtures in similar applications?

 

Have a question about efficacy or anything else? Our team of solar lighting experts is here to help. Reach out today to learn more about how to choose the right lighting solution for your project.