I love LEDs. Really, I do! They offer so many possibilities for new ways to light our world with less negative environmental impact. And besides, they’re cool! What I can’t stomach is the continuing hype. Frustration with LED hype is old news for lighting designers and for readers of this blog, but I thought by now it would have simmered down. It hasn’t. That LED Kool-Aid is still being poured and plenty of people are still chugging it down.

There are two flavors of this Kool-Aid that are really bugging me these days. Here they are:

Flavor #1: “Berry, Berry, Efficient”

Why are we still hearing unqualified claims about how LEDs are super-efficient? Claims like “use 80% less energy”, “seven times more efficient”, or the headline on a recent New York Times article, “LED Bulbs Save Substantial Energy, a Study Finds”. The question always should be, COMPARED TO WHAT?

So, based on manufacturers’ data, here is my grossly oversimplified analysis of how efficacious LEDs really are.

LED fixture efficacy compared to:

• Incandescent/halogen fixtures: 0 to 5 times better
• Compact fluorescent fixtures: about the same
• Linear fluorescent fixtures: 25% better to 50% worse
• Metal halide fixtures: about the same to 50% worse
• High-pressure sodium fixtures: about the same

So if I’m right, where are these claims coming from? They may start with misleading statements by manufacturers, but I think it is the popular media that is mainly to blame, for not doing the research and then promulgating bad information. This is picked up by the consumer and by public policy people, and then the more it is repeated, the more it must be true!

Here’s an example. The City of Boston is currently testing six different pedestrian-scale post-top fixtures on the Boston Common and asking for public reaction. Right on the project web site it says things like “Light Emitting Diodes (LEDs) use far less energy in producing more and better quality light than traditional lighting,” and “The large number of city street lights (67,000+) has the potential to significantly cut energy use and carbon emissions (currently 24,000 tons/yr) by switching to LED lighting,” and “High efficiency with the potential to offer 50 to 80 percent energy savings”.

Where do they get this stuff? Maybe it is the New York Times, but it could also be the manufacturers themselves. Right on the Cree web page talking about the Boston program it says “LED streetlights consume 50 percent or less energy compared to traditional streetlights”. I’m guessing that “traditional” is a significant qualifier in this statement, but I don’t know what they mean, and is the average person going to understand the distinction?

Flavor #2: “Numbers Crunch”

“Numbers Crunch” is the favorite flavor of LED product development engineers and marketers, especially those designing and selling LED lighting for streets and parking garages. They love to tell you about the amazing engineering that went into their fixture and how it delivers incredible numbers. The only thing they want to talk about is how the fixture delivers light to the ground, how awesome the uniformity can be, and how far apart you can space the poles. But what do these fixtures look like at night? Can I see well with them?

The true purpose of outdoor lighting is to make it easier to see at night, not to just deliver light efficiently to the ground. What we have seen with many LED outdoor fixtures is that they are very glary. Glare makes it hard to see. Sure, lighting the ground is important, but if the glare makes it harder to see, then it doesn’t matter how efficient the fixture is or how great the uniformity is. Sometimes I wonder if the engineers who designed these fixtures ever left their computer and stuck the fixture out on a pole at night and just looked at the thing!

So back to the Boston Common. I’ve looked at those six fixtures at night, and they perfectly illustrate what I’m talking about here. They all do about the same job of delivering light to the ground. But four of the six are terrible “glare bombs”. I don’t care what the numbers are, if the glare makes it hard to see and they’re unpleasant to look at.

OK, I’m done. Time to get a glass of cool clear water (or maybe a stiff drink!). What do you think?

Photos credit: Glenn Heinmiller / Lam Partners Inc

Tags: Boston, Efficacy, LED, Street lighting

This entry was posted on Monday, December 14th, 2009 at 9:00 am and is filed under TECHNOLOGY.