Choosing the Right CFL
How CFLs Work | When Not to Use CFLs | Choosing the Right CFL
There are some important factors to consider when choosing a CFL…
Physical dimensions: Make sure the bulb will fit in the fixture you are using.
Light output quantity: The light output of any lamp is measured in terms of "lumens". Make sure the CFL produces the amount of light you want. As a general rule of thumb, a CFL will produce 3 to 4 times as much light per watt compared to a standard incandescent lamp. For CFLs being used for outdoor porch lamps or ambient lighting in hallways, this general rule may be sufficient. However, because lumens per watt can vary by as much as 100%, for reading and task lamps it is imperative to match the lumen level of the incandescent with the replacement CFL. Avoid being displeased by mistakenly replacing, for example, a 100-watt, 1800-lumen incandescent with a 23-watt, 1200-lumen CFL. Instead, make sure that the replacement CFL matches the lumens output of the original lamp.
Note that over time, both CFLs and incandescent lamps lose some of their original lighting capacity. After 10,000 hours of operation (about 6-7 years if the light is used 4 hours/day), a CFL may lose about 30% of its original lighting capacity. Consider this "lumen depreciation" when deciding what CFL to use in each application. Although most manufacturers state that a CFL with ¼ the wattage could replace an incandescent bulb and produce the same light output, the more realistic rule of thumb is a three to one ratio (e.g. a 25 watt CFL replacing a 75 watt incandescent). This is the ratio SafeClimate uses in its lighting comparison charts.
Light quality: There are two key considerations: the color "temperature" and color temperature rendering index. Among CFLs, and between CFLs and other lighting options, there are measurable differences. CFLs usually can be purchased with color temperatures ranging between 2700 and 4100 K. The lower temperatures provide a softer, warmer color. For example incandescent bulbs are rated between 2700 and 3000 K. The Color Rendering Index (CRI) is a measure of a light source's ability to illuminate true colors. A CRI of 80 or above indicates that the light source can reproduce colors accurately. Note, that all CFLs sold through SafeClimate have color temperatures of 2700 to 3000k and have CRIs of 80 or greater. For more information see the color temperature and color rendering index (CRI) chart posted by the Energy Outlet (Eugene, Oregon).
Weight: CFLs tend to be heavier than their incandescent counterparts, though the difference is smaller where the CFL uses an electronic ballast. Some fixtures, such as floor or table lamps may become top heavy and unstable with some CFLs. A good rule of thumb is to avoid using a CFL in portable table lamps where the distance from the bottom of the base to the top of the lamp exceeds three times the minimum base width.
Ambient temperature range: If your bulb is going to be exposed to extreme temperature variations (such as in outdoor applications in fierce climates) check the packaging or other information sources to make sure the CFL can operate properly in the expected temperature range. For example many CFLs require a temperature above -20 degrees Fahrenheit in order to switch on.
Dimmers: If you are going to use a dimmer, make sure you use a CFL with a dimmable electronic ballast that can be used on the circuit. Many CFL ballasts will not work with dimmers and in fact can pose a fire hazard if used with a dimmer. Verify that the dimmer or other control device (such as an occupancy sensor) is compatible with the CFL you wish to use. Since dimmable CFLs typically cost about double their non-dimmable counterparts many consumers have opted for other solutions where dimming is necessary.