How many environmentalists does it take to change a light bulb? Well, that depends on how hard they're willing to work at it.

OK, bad joke, but it's a true story. I've been changing incandescent light bulbs over to compact fluorescent in a piecemeal fashion, but finally decided to switch in one fell swoop. I was only 25 percent successful after some considerable effort. Here's the story:

Eighty Light Bulbs, No Two the Same

Four years ago, when I timidly replaced my first bulb, a single CFL cost $15. Ouch. After a few $15 bulbs that made my apartment look like a dimly lit subway station and two that failed instantly when I put them inside globe lights, I took a hiatus from light bulb changeovers. But the new lower prices and the promises of better light spurred me to try again.

Who knew I had 80 incandescent bulbs in my apartment! Six bulbs in the ceiling fixture, four bulbs in the small sconces, two floor lamps—and that was just the living room. I never even bothered counting appliance bulbs (refrigerator, microwave, and oven) because they are not on much.

Once I'd inventoried bulbs, I divvied up bulb types. Turns out that I have more bulb types than most tulip gardens: PAR 20 indoor floods, little bulbs used in my undercounter kitchen lighting, bulbs that look like old fashioned Christmas tree lights, small bulbs, small and medium base candelabra bulbs, a halogen bulb in the shower and a few other halogen double ended T3s, two different low voltage desk lamps, and more. Complicating things, some rooms have dimmers. Dimmable CFL bulbs exist, but probably not in the size/type/wattage or whatever that you want.

I decided to replace the bulbs that are most used and most readily available in CFL. The four-bulb, 40-watt candelabra in our dining room is always on and there's no dimmer. So I picked up four 9-watt equivalents, and they work pretty well, delivering about the same light, but saving 124 watts for long periods of the day. Easy victory.

The replacements I bought for the bathroom fixture didn't fit because the three 20-watt CFL bulbs they required had thicker necks than the incandescent lights they replaced. I backed off to 14-watt CFL bulbs that were a tad skinnier, but dimmer. I'm saving just over 180 watts for the hour a day that light is on. (Note to self: Spend more time in bathroom.) Our second bathroom got 20-watt A-shape CFLs, which save about 60 watts, though for not-many-hours a week. I used a few other CFL A-shape bulbs in floor lamps in the living room and bedroom. The ceiling fans required four PAR 20 small indoor floods. The replacements, 14-watt CFLs cost $11 each, gulp. I'm saving 144 watts, but that's probably only a few hours a month.

Tallying the Score

It took a few shopping trips, virtual and real, to get my bulbs. I bought my candelabra and PAR 20 floods at Bulbs.com, my first two A-shape bulbs at a supermarket, and then my last six A-shape bulbs at Wal-Mart. Total cost $150.

I was surprised by how many bulbs I couldn't replace. I decided not to try and replace the bulbs in my home's sealed fixtures based on past experience with blown out CFLs. I couldn't replace the small candelabra bulbs because I couldn't find a dimmable CFL candelabra bulb. Bulbs for my sconces don't seem to be available anywhere. I didn't try to replace any under-the-counter bulbs, but I suspect they aren't available because I haven't seen any other CFL bulbs that small. Maybe when LED technology is more developed some of these smaller bulbs will be replaceable with efficient alternatives. The double-ended halogens just aren't replaceable with CFL.

There you have it. Eighteen bulbs were all I could replace of the 80 in my apartment. My estimate is that I'm saving about 1,500 watt-hours a day, mostly from that one dining room fixture. My electricity costs about 18 cents per kW-hour, and I'm saving 1.5 of them each day. That's just over a quarter a day, or perhaps $90 a year.

This turned out to be a bigger project than I imagined (thanks to my husband who spurred it on). All is not perfect. CFL lights take longer to light up than incandescent bulbs. They light up to 75 percent capacity almost immediately, but brighten slowly from there. They contain mercury and must be disposed of properly when the time comes. But the biggest con is that CFL bulbs are never the same shape or wattage as what they replace, so you need to be very careful.

Despite it all, I feel virtuous. And, because these bulbs last so long, I probably won't be revisiting these fixtures for a long time. In warm weather, I'll appreciate the reduced heat of these efficient bulbs, too. And at some point after I make back my original $150, towards the end of 2008, I'll actually start to save money!

For more on light bulbs:

LED bulbs

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