Compact fluorescent light bulbs can save you quite a bit of money on your electric bill, provided you can get the bulbs at a good price. Here are some tips to take into account when you consider replacing your standard incandescent bulbs with fluorescent bulbs.
1. Physical fit. A critical consideration when planning to replace traditional incandescent bulbs with compact fluorescent bulbs (CFLs) is the physical space available in the light fixture. Many of the newer CFL bulbs are small enough to fit into the same space as the bulbs they replace. Some of the older CFLs were substantially larger and would not fit into closed fixtures.
2. Light output. The amount of light output or brightness of a bulb is measured in lumens. A 60-watt incandescent bulb might put out about 900 lumens, while a CFL of 13 watts might also put out 900 lumens and a 14 watt might deliver 970 lumens. The CFL package will contain a large "60-watt" label (or if the manufacturer is more honest, "60-watt equivalent"). Those wattages are just for reference--if you used a 60-watt incandescent, then this is the bulb for you (at 13 or 14 watts).
3. Color. Light, even what we think of as white light, has a range of whiteness to it, indicated as a color temperature. The standard, soft white light we usually see inside the home, lit with ordinary incandescent bulbs, is 2700 degrees Kelvin. Daylight bulbs, which seek to reproduce the color of bright sunlight, have color temperatures of 5000 to 6500 degrees Kelvin. If you are considering changing your standard incandescents to CFLs, then I suggest you choose 2700-degree bulbs. If you have an at-home office, and you want the relatively harsh, bright light of noonday sun, then choose the bulbs labeled "daylight" at 5000, 5500, or 6500 degrees.
4. Instant On. Early CFLs, when turned on, started out rather dim and required a few minutes to achieve full brightness. This becomes an irritation after awhile. My recommendation is that you make sure the label on the box says "Instant On" or don't buy the bulb. The only exception would be for bulbs you plan to leave on all the time or run from dusk to dawn, such as porch lights.
5. Radio Interference. CFLs tend to generate radio interference. When I pull into my garage, which has two CFLs in the garage door opener, my AM radio program is drowned out by static. Consider this effect when planning your replacements or installations.
6. Cost and Savings. The length of life listed on the box (7 years, 9 years, etc.) is mostly bogus, based on leaving the bulbs on all the time. Turning the light on and off frequently tends to shorten their life. If you make a dozen trips a day to the closet, pantry, bathroom, etc. and each time turn the light on and then off, you might get 3 or 4 years from the CFL. The cost of CFLs varies widely. I've seen essentially the same 60-watt equivalent CFLs on sale for $4.88 for four ($1.22 each ) and at another store $12.98 for five ($2.59 each). Some electric utilities offer CFLs at subsidized rates, so check with your utility and hardware stores.
7. Disposal. Because fluorescent bulbs contain mercury, a toxic metal that must be kept out of groundwater, the bulbs should not be put in ordinary trash after they fail. Fluorescent bulbs should be taken to your nearest hazardous waste facility.
8. Startup Tip. When you install a brand new CFL, turn it on and leave it on for 30 minutes or so. You'll notice that even instant-on bulbs don't fully light the phosphors all the way through the tubing in the bulb. But after burning them in for 30 minutes or so, the bulbs will be ready to start fully bright each time you turn them on in the future (unlike the old, non-instant-on bulbs).
Compact fluorescent bulbs offer some advantages over the incandescent bulbs they replace. You can leave a bulb on as a night light because the wattage is so low. I have a nightlight that uses a 7-watt CFL bulb and it lights the entire room. CFLs last longer that incandescents, so if you have some difficult-to-change areas (such as high ceilings), then you can reduce the hassle with CFLs.