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

Light pollution and light trespass are hot exterior lighting topics, and they both relate directly to the broader topic of energy conservation. Simple logic tells us that shooting light into the night sky, either directly or inadvertently, is basically a waste of light and energy. The light that escapes above the horizon hits nothing but air, water, and smog. Some of that light is reflected back down as light pollution, that eerie yellow glow that obscures the stars, but none of it is useful – it’s an unutilized byproduct of the artificially illuminated environment.

That’s not a good thing! Sky glow and light trespass have been linked to problems like sleep disorders, migratory bird death, and obstruction of the night sky. Small problems that may seem insignificant? Well, think of it this way: sky glow exposes how much energy and money we pump into the air, and guess who pays for all that extra light – you, the taxpayer! Millions and millions a year, and most of it is powered by fossil fuels.

Can we simply turn off all the exterior lights then? No, unfortunately, the lighting was probably installed in the first place to serve a purpose: the lighting of streets, buildings, parks, and other places that people navigate to at night.

Could we reduce the amount of exterior lighting, though? We can already discern that a lot of lighting is wasted in the sky. Could it also be possible that we’ve intentionally lit that which should not or need not be lit to begin with – that the purpose served was not a legitimate, well-conceived purpose? Absolutely!

Since the invention of the light bulb, we’ve been putting electric lighting EVERYWHERE. We did it because we needed it and wanted it, to see where we were walking and driving (street lighting), to see where we were going (sign lighting), because it looked nice (decorative lighting), to show off our accomplishments (building and bridge lighting), to illuminate nature (tree uplighting), and for security and safety (the former as a police control measure and the latter as a matter of perceived personal well-being).

Now some designers are taking another look at the “why” of design, questioning whether or not we really need all that lighting. Do we need to light a stretch of rural highway when we have headlights on our cars? Do we need to light city centers to 50 lux (5 footcandles for you Imperialists) when 20 will do? It’s not just a question of yes or no, but also of how much.

To take a few of these examples, here are some issues that we should think twice about:

• Street lighting – do we need to light roadways so much that we can do without headlights entirely? (I’ve seen it – no headlights! Insane!) Perhaps we can use the task-ambient approach here: ambient from very low-level street-based systems, and task from headlights. We’ll still need to pay attention to the vehicular-pedestrian intersections but all that lighting in between could possibly be reduced.

• Sign lighting – do you really need to light your signs all night long, from the bottom shining up? What if you turned the sign off after midnight, and lit it from above?

• What about building lighting? Many developers, architects, and designers want to see their projects as the beacon of the neighborhood. Uplights graze the columns, floodlights slam into concrete walls, and twinkly lights adorn the penthouse. Should every building do this, though? Are they entitled to? What if the desire to be the best on the block simply precipitates escalation of building lighting – where does it end? Everyone needs to ask themselves “Should I even light the outside of this building?” That goes for public monuments, too; maybe we should take public money used for lighting public monuments and put it somewhere more useful, like healthcare. How about focusing on the entry and letting the rest go dark at night?

• How about landscape lighting – why? We light the trees and shrubs only because we can. Yes, it does look pretty, but at what expense? The amount of light the canopy of any particular tree can catch in comparison to what shoots straight into the sky is very little.

• And finally, lighting for security and safety. This is a very sensitive issue. Police officers, emergency response professionals, and the general public would prefer more light as opposed to less. The popular opinion is that more lighting equals less crime and, while more light will certainly help the police in identifying perpetrators, it doesn’t necessarily create safe environments. There are very well-lit alleys in which all sorts of crimes happen. The statistics have too many variables to pin down an unquestionable correlation. Maybe we should concentrate on good quality lighting that serves these purposes without increasing light levels. Better lighting, not more!

All of these applications are only marginally effective, which supports the position that we simply do not need as much lighting as we have. If a total of three people drive by a building at 3:00 a.m. and see it lit up, is keeping it illuminated all night long worth the collective fifteen seconds of viewing?

Every developer, architect, or designer should question if it’s really worth it. But then, it’s a hard question to ask – who’s to say what qualifies and what doesn’t? Who will speak up and tell someone “no”?

Photo Credits: Liber (1), Ian Plumb (2), Clav (3)