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the Right Light

by Michael Potts

Light is the best reason for bringing electricity home. Kerosene, candles, and gas lamps all consume precious heritage resources, and all pollute and threaten the indoor environment, and generations of students and readers will agree: they give off a crummy kind of light. Over the homework table, workbench, sink, stove, or bed, simple, clean, silent electricity glows almost as satisfactorily as the sun.

In this project, you may learn how incandescent and fluorescent lights work, review the economics of light, practical considerations of lighting, and look at a map of suitable lighting applications. If you do your homework, you can save about 60% of your present lighting bill while doing the planet a favor.

Electric light has brightened lives for scarcely a century now, and already there is a revolution in the technology. Most of us enjoy the warm and mellow light thrown by Edison's incandescent bulb. But incandescence literally means heating a wire filament with a torrent of electrons until it glows. Less than a fifth of the energy is converted to light; the remaining four-fifths produces waste heat. Adding insult to injury, in a cooling regime where energy is used to refrigerate air like Texas in summer, this waste heat can add 10% to 20% to cooling loads and costs.


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Tradition recounts that Edison derived his wisdom on the relationship between invention, inspiration, [ Incandescent lights works by burning electricity ] and perspiration while trying to solve the problem of the short life of an incandescent filament. Modern tungsten filaments work fairly well, lasting an average 1,000 hours. Tungsten is a limited resource, one of the strategic metals most sought in dump mining; it makes sense to separate blown bulbs from other glass garbage.

One thousand hours is shorter than it seems. An incandescent bulb burning 8 hours a day is scheduled for burnout after a mere four months. Decades ago, industrial lighting experts forsook incandescent bulbs at most commercial installations. Fluorescent tubes, the simplest low-energy substitute, generate the same light with between 20% and 25% of the energy, and generate about a quarter of an equivalent incandescent bulb's waste heat, but to the maintenance crew, the best news is that a typical fluorescent tube lasts 10,000 hours, or ten times longer. If you spend your day changing bulbs under a 30 foot ceiling over the heads of ungrateful workers, you understand.

For those of us weaned under incandescent light's golden glow, fluorescent light always has a cold unfriendliness to it. We may be reassured that phosphor chemistry has responded to our preference by chemically tuning the fluorescent glow until the average modern tube is truer to the sun's spectrum than an incandescent bulb's.

[ fluorescent lights work by exciting electrons ]
Early tubes flashed demonically like strobe lights, sending sensitive folks over the edge into headaches and worse. Poor shielding and misunderstood energy turned the ballasts and energy handlers into legendary sources of exotic electromagnetic pollution. In one famous Canadian experiment, blind students were shown to experience learning problems when instructed under the electronic hash coming from poorly shielded early ballasts.

In thirty years of stepwise electronic refinement, these problems have faded into historical memory in all but a few ill-lit legacy fluorescent installations where original tubes still flicker valiantly. Compact fluorescent bulbs (CFs) are the most recent innovation. The same technology as in the four-foot tubes, but miniaturized and folded into roughly the same form factor as an incandescent bulb, these slick little devices can meet almost every lighting challenge with efficient fluorescent lighting.


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The Economics of Right Lighting

the compact fluorescent went on over her head Every technical objection being answered, it is no longer possible to make a good rational argument against fluorescent lighting …except one. Incandescent lights are ridiculously simple from the electrical perspective, and simple translates into cheap, particularly when the technology has matured to the scale and universality of the light bulb. Initial wiring is trivial, and fixture and equipment cost is very low. A low-cost fluorescent fixture may cost twice as much, and compact fluorescent bulbs typically cost more than $20. How can a mere light bulb ever recoup that kind of up-front cost? For Mr. and Mrs. American Consumer, it's counter-intuitive.

Of course real economics carefully considers operating cost plus equipment cost and quickly concludes that even expensive compact fluorescent bulbs are a great bargain, often saving twice their cost over their lifetime. Here is a typical California breakeven scenario:


Breakeven: Compact Fluorescent vs. Incandescent
Breakeven calculated for
13.2 cents / kilowatt hour
    60 watt incandescent lightbulb      12 watt compact fluorescent
       equipment  operating               equipment  operating
hours      cost    cost     total             cost    cost     total
     0     0.60              0.60            23.00             23.00
 1,000     0.60    7.92      9.12            - 0 -    1.58     24.58
 2,000     0.60    7.92     17.64            - 0 -    1.58     26.17
 3,000     0.60    7.92     26.16            - 0 -    1.58     27.75
 4,000     0.60    7.92     34.68            - 0 -    1.58     29.34
 5,000     0.60    7.92     43.20            - 0 -    1.58     30.92
 6,000     0.60    7.92     51.72            - 0 -    1.58     32.50
 7,000     0.60    7.92     60.24            - 0 -    1.58     34.09
 8,000     0.60    7.92     68.76            - 0 -    1.58     35.67
 9,000     0.60    7.92     77.28            - 0 -    1.58     37.26
10,000     0.60    7.92     85.80            - 0 -    1.58     38.84
          =====   =====                      =====   ===== 
 totals    6.60 + 79.20  =  85.80            23.00 + 15.84  =  38.84

 percent   7.7%   92.3%                      59.2%   40.8%
 of total  

The compact fluorescent's TOTAL cost is $56.96 LESS than the TEN incandescents it replaces!
To calculate what YOU can save, check out our new
Tech in the Box : Compact Fluorescent Economics
For Netscape/Java users only, Netscape 2.0 or better required!
If you are running some other browser, your results may not be predictable.

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There are still places in America where local electric utilities give away closets-full of incandescent light bulbs because they want ratepayers to use as much electricity - typically coal-generated - as possible. The Department of Energy, the agency charged with knowing stuff like this, says that the average domestic ratepayer spends a little over 8¢ for a kilowatt-hour of electricity. As can be seen in the following graph, compact fluorescent bulbs are marginally cost-justifiable for anyone who pays less than the national average. For the rest of us, efficient CF light makes more sense the more we pay.

[ a CF save almost $50 over its lifetime ]

note: the lines in this graph represent the compact fluorescent advantage which is negative, of course, until the operating cost advantage overcomes the initial equipment cost disadvantage. When the line rises above zero, the compact fluorescent bulb has cost less than the equivalent incandescent bulbs.
In a future project, SUN plans to conduct a kilowatt-hour survey in order to make a real world map of kilowatt-hour rates. When calculating your rate, be sure to pro-rate any "connection fees," taxes, hidden charges and surcharges assessed by your utility. If anyone can explain why electric bills must be so confusing, we would be thrilled to reprint the explanation here.

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The Practicalities of Right Lighting

Change offers us an opportunity to improve function as well as economics. In this project, you are invited to undertake a lighting makeover for your home. Many of us live with lighting schemes that were conceived for the convenience of the electrician and the architects, not the inhabitants of the home. In many cases, this has proven unsatisfactory.

After a century, we are becoming more discerning in our lighting choices. In the 1940s, the height of utility was two 60-watt light bulbs in a big fixture in the middle of the kitchen ceiling, cunningly placed so that the cook prepares food in his own shadow. In many kitchens' this fixture was replaced by a cheaper-to-operate fluorescent fixture that cast a slightly more diffuse light on the subject (always assuming that the subject is not four feet wide.) In the wake of the oil embargo and the onset of energy consciousness, lighting designers noticed this problem, and invented task lighting.

  • if the primary light source in a room comes from a fixture in the middle of the ceiling, evaluate the suitability of the light. Consider updating light delivery systems.
  • if the present fluorescent fixture flashes, consider changing to a more efficient electronic ballast which flashes much faster than the brain can perceive.
  • if your fluorescent tubes flicker or are dark at the ends, replace them with newer, more efficient tubes. Modern tubes are smaller but actually generate more light due to improvements in phosphor chemistry.

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Suitable Lighting

[ suitable lighting choices map ]

Compact fluorescent bulbs are great for some locations, and have problems in other places. For example, any light that is typically on for two or more hours a day SHOULD be a compact fluorescent. Lights on dimmers CANNOT be CFs. The lives of all bulbs, including CFs, are shortened by lots of switching on and off. CFs are likely to fail prematurely in places where the electricity is junky, for instance on unconditioned generator-powered systems. CFs sometimes have trouble starting when it's cold or the electricity is weak. Here's a list of places in the home and our thoughts about bulb choices, including a few where the bad old incandescent bulbs are probably still best:

Attic & Closets:
It might take a couple of lifetimes for CFs to get to breakeven, so swap other lights first.

Surface-mounted Wall and Ceiling fixtures:
Be sure the larger compact fluorescent fixtures fit inside the cover. On multiple bulb fixtures, you can often increase the amount of light dramatically while decreasing the cost of electricity. (You can substitute 2 or 3 90-watt equivalents for 2 or 3 60-watt incandescents, which adds 50% more light for 50% less electricity!) Waste heat is not the problem it was with the original bulbs.

Reading lights:
A classical task, and an invitation to use task lighting. Here's where to use those sexy little low-voltage halogen lights. Halogens are efficient only in that they last longer and create more light per kilowatt, but they are ferocious little incandescent heaters. Their redeeming feature is that their light can be intensively focussed on the work and only the work. These also work well over work surfaces.

jump to map of suitable light sites : return to map of suitable light sites :
Ceiling "Can" fixtures
Cheap and easy to wire, so electricians have been using too many of them. Most of them are too short for even the short-form compact fluorescents, so measure before you buy. (Some people think they look kind of space-agey and cool with little fluorescent tubes sticking out.)

Table and Floor lamps:
CFs work great, but there are two things to watch for, harp length and balance. The harp is the wire that holds the shade. Socket- and harp-extenders can usually be used to retrofit most lamps. CF ballasts are a little heavier than old-style bulbs, and may make flimsy lamps top-heavy. (It's a terrible shame to see a $20+ bulb in shards on the ground - there goes breakeven!)

Outdoor lighting
One of the best applications for CFs because sometimes these bulbs burn throughout the evening or all night, and savings can be significant. Furthermore, such bulbs are sometimes a real pain to replace. CFs don't do well exposed to the elements, and so should be in enclosed fixtures, and northern tier folk should read the part about operating temperatures, since some bulbs are hardier than others.

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Fluorescent tubes:
Modern fluorescent tube lighting has the highest quality color temperature and color rendering index available, so the bad old rap about blue light is history. No light-source is better for sizable tasks like cooking or workbench. Not to be sneezed at.


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updated 1 January 2005 : 16:37 Caspar (Pacific) time
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