Compact Fluorescent Bulbs - Switching for Efficiency

Abstract: Compact fluorescent (CF) bulbs can be used advantageously in many home lighting applications -- offering much longer bulb life and considerable savings in the electric bill. However, they differ radically from tungsten filament bulbs (incandescent and halogen types), so you need to consider: when to turn them on and off, where not to use them, and their environmental hazards.

The conventional wisdom: Standard incandescent bulbs are very inefficient, putting out only 10-15% of the electricity they consume as light - the rest is dissipated as heat. But they are cheap and we are accustomed to the warm, broad spectrum light they provide. Halogen (also tungsten incandescent) bulbs are very slightly more efficient, last a bit longer, and have a pleasant, brilliant light quality; but they cost slightly more than conventional bulbs and achieve little if any energy or cost savings.

Compact fluorescent (CF) bulbs, only 2-5 times more expensive per bulb now than incandescents and halogens, are about 4 times more efficient in light output -- a 13-15 watt CF puts out the equivalent of a 60 watt incandescent or a 50 watt halogen. And they last 5-10 times as long as regular tungsten filament bulbs; so, between much longer life and much greater electrical efficiency, they are significantly less costly to operate, and their widespread use would save significant energy on a national and global scale, with all the benefits that would accrue from that.

There are excellent articles about bulb types and efficiency/cost issues at these sites:

Lowes.com light bulb guide:
http://www.lowes.com/lowes/lkn?action=howTo&p=BuyGuide/LightBulbBG.html

Wikipedia has excellent article on CF's & good discussion of environmental hazard:
http://en.wikipedia.org/wiki/Compact_fluorescent_lamp

General Electric site has cost calculator to compare annual, life-cycle, and per-lumen cost of various bulb types:
http://www.gelighting.com/na/business_lighting/education_resources/tools...

BUT the conventional promotion of CF's ignores several important issues, so here are --

A few contrarian considerations:

1. CF's and tube fluorescents are made to have various color spectral outputs, from warm, soft white, like incandescents, to natural, like sunlight, to cool-white. Try them out at the store to see what you like. Putting different spectral types in one room might show unpleasant color contrasts.

2. CF's will fit your standard (medium) sockets, but some profiles may not fit in your (table or desk) lamps if shade bow is too narrow. Socket extenders may or may not help.

3. CF's can be dangerous if used in the wrong places: outdoors if exposed to water -- be sure they are rated for exterior use; in enclosed fixtures, i.e. where glass shade/cover prevents air cooling, the elevated temperature can shorten life or cause fire; with dimmers, could overheat, cause fire -- dimmable CF's are sold, but are much more expensive.

4. Switching on and off -- with tungsten filament bulbs it is always beneficial to switch them off immediately when light is not needed, i.e. as you leave the room; but with fluorescents the question is much more complicated because each on-off cycle shortens bulb life. In fact, when I first tried switching to CF's about 10-12 years ago and put them in locations where I would normally switch them on and off several times a day, they burned out very quickly -- far sooner even than an incandescent in that location. I tried different makes and styles and all were disappointing. But, my anecdotal experience of years past may not be generalizable. I may have just had bad luck with several and manufacturing technology may have improved. My current way of using them, described below, using newer CF's has been more favorable. The US Dept of Energy gives different advice on their web site; they say that it is most cost-effective to switch off a CF if doing so will save 15 minutes of electricity use; but I think the question is still unresolved as to how much on-off cycling shortens bulb life --
http://www.eere.energy.gov/consumer/your_home/lighting_daylighting/index...

5. Waste heat is not wasted in winter. All conventional discussions of energy savings with CF's assume that an incandescent bulb's turning 90% of its wattage into heat is wasted. In winter, when you are heating your house with some energy source, that is not wasted energy. Admittedly, the cost per BTU of resistive heating like this is several times the cost of natural gas or heating oil. But the glowing bulb also gives some radiant heat if you are close to it, so may allow a lower room ambient temperature (see discussion elsewhere of radiant vs. convective heat sources). Example: my house has 2 heat zones (natural gas, hydronic system). I keep the lower level fairly cool in winter (60-62 deg F.); I have an office on that level that I use a few hours per day. When I'm in it, I'll typically have one or two incandescent bulbs and 1-2 CRT monitors on and they keep it a comfortable 67-68 degrees. I avoid heating the entire 1400 sq. ft. zone just to make this one room comfortable.

6. The opposite argument obviously prevails in summer -- heat from incandescents is usually unwelcome, and would add to cooling load if you're using some kind of active cooling (fans, A/C, etc.).

Considerations 4, 5 and 6 have led me to the following way of using CF's (subject to change if I learn more):

7. How I use CF's now (2004 to present): I keep a 13 w. spiral CF in an outside post light year-round -- it is switched by a photocell on the post -- on at dusk, off at dawn. I've read that some CF's won't work with photocell switches, but this one does fine. I'm using a regular interior bulb, but the housing protects the bulb sufficiently from water. There is sufficient air circulation to keep the bulb from overheating. Year-round, my garage-workshop has several overhead 4 ft tube-type fluorescent fixtures with a mix of cool-white and warmer bulbs. I only turn them on when needed, and then leave them on if there is a chance I will be in the workshop again within an hour or two -- i.e. I try to cycle on-off at most once daily, but sometimes more than this. Same pattern with some under-counter tube fluorescents in my den/bar area. In winter I use mostly incandescents in indoor lamps, but I am quite diligent to turn them off unless I'm in the room. In summer, to avoid incandescents heating the house, I change several bulbs over to CF's and try to cycle them on-off at most once daily. I do NOT put CF's in areas where I'm constantly turning lights on and off or switching them on very briefly -- bathrooms, closets, den track lights, laundry/utility, and obviously where there are dimmer controls (dining room, kitchen ceiling). CF's would certainly NOT be suitable in a motion-sensor switched fixture that is frequently cycling on and off.

8. CF's (indeed all fluorescents) contain mercury and must be recycled appropriately (NOT in your usual trash or recycling bin). Broken bulbs must be carefully cleaned up and recycled. Reportedly big retailers like Home Depot and Walmart will soon have provisions for safe CF recycling. I see very little written so far about the pollution from manufacturing CF's. It's all done overseas, so if they save us money, who cares if China and Hungary are contaminating their land, right? If you compare the very simple nontoxic ingredients in a standard bulb to the complex electronic circuitry, solder, plastics, mercury and rare earth elements in a CF you may think a little more about their global impact.

Recycling sites for your area: www.earth911.org

Article about CF mercury content:
http://www.popularmechanics.com/blogs/home_journal_news/4217864.html

More at: www.lamprecycle.org

Print reference:
http://www.amazon.com/o/ASIN/0916571068/ref=s9_asin_title_1-1966_p/002-1...
-- Real Goods Solar Living Sourcebook (new 30th Anniv. edition published fall 2007) has detailed article about various types of electric lighting -- and much more about all aspects of energy efficiency, off- and on-grid home power systems, etc. Combination of educational articles and product catalog.