Field Tested: Full Spectrum Lighting

Jeff Klein
Jeff Klein

For decades, “full-spectrum lighting” has been a popular but misunderstood topic. Its premise is that electric lights that produce the same wavelengths of light as the sun will confer improved health and mental cognition.

But while the marketing of “full-spectrum lighting” has been successful in convincing many buyers than it offers improvements over traditional fluorescent lighting, the reality is it does not. And it’s generally a waste of money, too.

The falsity of these premises have been demonstrated over and over again in review articles of the scientific literature that review dozens of studies. The National Research Council of Canada, has compiled several reviews of studies and here.

The reason for this mistaken hype is that “full-spectrum lighting” is a sales concept and not a scientific standard. And it is an effective sales concept, too: full-spectrum lights sell at a hefty premium compared to regular fluorescents, too. They can cost five times as much or more.

Yet, compared to traditional fluorescent lighting like T5 or T8 lamps in buildings, full spectrum lighting does not improve memory tasks or reduce sick days or treat Seasonal Affective Disorder (SAD) any better than regular fluorescents.

From an energy perspective, full spectrum lights are not ideal, too. On average, full spectrum lights have a lower efficiency– technically called efficacy and measured in Lumens per Watt [link to our blog post on this topic of 683 lumens per Watt] – than common office building fluorescents like T8s and T5s.

The National Lighting Product Information Program (NLPIP) – an independent light testing laboratory supported by the government and major utilities but not lighting manufacturers – analyzed the costs and the price premium of “full spectrum lights”.

We can see that there is little difference between for “full spectrum” and “non-full spectrum” lights. This is a map of something called Spectral Power Distribution. it is the amount of light emitted by a light bulb for each individual wavelength of visible light. The range of colors of light emitted are nearly identical, meaning the two light types are producing almost exactly the same light. One costs three times and much and uses more energy on average, and it is the “full spectrum” light.

The colors of light emitted are related to but different from another important concept called the Color Rendering Index or CRI. CRI is a measure of what percent of colors can be differentiated under a particular light. For example, sunlight has a CRI of 100, because under it all the colors on a representative color palate can be easily differentiated. A CRI of 80, typical of most fluorescent lights is more than adequate for most office, industrial, and educational needs, but might not be ideal for an artist’s studio. While full-spectrum lighting can have higher CRIs, for most real-world applications, a CRI of 80 is all that’s needed.

As LED lights become ever more cost-effective replacements for fluorescents – though often they are still not worth the cost in terms of energy savings— concepts like lighting wavelengths, CRI, efficacy, and other quantifiable concepts matter greatly when measuring financial results from energy retrofits. But there are also concepts, like “full spectrum lighting,” that are not scientific in nature that improve neither health nor performance nor the environment.

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