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Monday, May 5, 2008 10:26 AM UTC

Ask Pablo

LED lights are amazing but expensive. By switching to them, will I save energy and money over the long run?

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Topics: Environment, Energy,

Dear Pablo,

I would like to use LED lighting to replace all my existing lighting. Over the long run, will I be reducing energy consumption and pollution, and even saving money?

I have written a lot about the environmental benefits of compact fluorescent (CFL) light bulbs in the past, but never about LED light bulbs. LED stands for “light emitting diode” and is a semiconductor diode that emits a narrow frequency (color range) of light. To put it simply, think of it as a solar panel in reverse: Electricity goes in and light comes out. To answer your question, I requested LED light bulb samples from LED Waves, and received a high-power 7-watt LED bulb that emits 500 lumens, has an anticipated life span of 50,000 hours (that’s almost six years, 24 hours per day), and retails for $59.95. Since LEDs are directional — they emit light in a focused beam rather than in all directions, like a conventional light bulb — it is difficult to compare them exactly to CFLs or conventional incandescent light bulbs. But I will try to provide a comparison of their light output, energy consumption and cost-effectiveness.

A 7W LED can be compared to a 10W CFL, which also emits 500 lumens. The closest incandescent bulb that I could find was a 460-lumen or 40W bulb. The next thing is to compare the efficacy of the bulbs. This is done using the measure of lumens per watt, or light emitted per electricity input. The incandescent bulb has an efficacy of 12 lumens/watt while the CFL has an efficacy of 50 lumens/watt, only to be outdone by the LED at 71 lumens/watt. So it’s clear that LEDs are by far more efficient than incandescent bulbs. But does this justify forgoing CFLs in favor of LEDs? At over $50 per bulb, the high upfront cost will give everyone pause. But is the long lifetime or the high efficiency worth the cost?

A 10W CFL, available online for $6.90, has an expected median lifetime of 10,000 hours. While this is about 10 times longer than the life expectancy of an incandescent bulb, it is only one-fifth the expected life of the LED. So LEDs have the potential of cutting down on ladder time by a factor of 50 over incandescent bulbs! At about 25 cents apiece, the incandescent has by far the lowest upfront cost, which is why many people still use them. If we normalize the cost of all the bulbs over a 50,000-hour period, the incandescent bulbs cost $12.50, while CFL bulbs cost $34.50, and the LED bulb costs $59.95. But, as you may already know, the upfront cost of a bulb is by far the cheapest part. It’s the electricity required to operate the bulb that adds up.

Over a period of 50,000 hours, a 40W incandescent bulb will use 2,000 kilowatt-hours (kWh). At 15 cents per kWh, this will put $300 in the pocket of your local utility, bringing the total cost of the incandescent bulb, over 50,000 hours, up to $312.50. The CFL bulb only uses 500kWh over the same time period, or $75, totaling $109.50. Finally, the LED bulb will use 350kWh for $52.50, with a total cost of $112.45. So, in this example, the LED light does cost a few dollars more but the difference is negligible. Think of the time you will save by not running to the store to buy bulbs and climbing the ladder to change them.

As for their disposal, LED lights, unlike CFLs, contain no mercury and many of them are compliant with the European Union’s Reduction of Hazardous Substances (RoHS) directive. Like CFLs they do contain electronic circuits, which are hard to separate back into individual materials for recycling. But with a life span of 50,000 hours, the relative amount of waste created will be quite minimal.

There are still some limitations to LEDs. The best idea is to figure out your lighting needs and speak with a lighting professional at a local lighting store or at LED Waves to find the solution for you. Be sure to tell them if you are looking for area lighting or spot lighting, bright light or colored light, indoor or outdoor, on/off or dimmable. There are a growing number of options in the LED bulb market and you should be able to find the right bulbs for you. An exciting lighting innovation that comes with the commercialization of LED lighting is the versatility of LEDs in creating changes in brightness and color using a computer controller. It’s now possible to wake up to a simulated sunrise or to set the mood for a romantic dinner at the touch of a button.

Got a question about the environment? Ask Pablo at AskPablo@Salon.com.

Got a question about the environment? Ask Pablo at AskPablo@Salon.com. More Pablo Plastic.

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