There are some drawbacks to covered CFLs, however, and you should know that before choosing them over spiral bulbs. Because the cover traps heat, these bulbs use a mercury amalgam requiring a higher temperature for the bulb to reach full brightness. So they take longer to produce all the light they're capable of. While a spiral might reach full brightness in 60 seconds or less, a covered bulb might take closer to 3 minutes.
As a result of the higher temperatures, a covered bulb also has a shorter rated life span. A spiral bulb could last up to 10,000 or 12,000 hours (check the packaging for the rated life) while a covered bulb might only be rated for 8000 hours. This is still a much longer life than an incandescent bulb.
When choosing either type, it's important to remember some things about CFLs in general:
- CFLs are best used in locations where bulbs are typically left on for more than 15 minutes at a time. Shorter "on/off" cycles can significantly reduce the life of a CFL. If you'll only use a bulb for a few minutes at a time and/or it will be turned on and off frequently, consider upgrading to LED lighting. Click here to see some of our best values on LEDs for home and office settings.
- CFLs come in a variety of color temperatures. If you're trying to approximate the feel of an incandescent bulb, make sure to choose a CFL with a Kelvin rating of 2700K (shown on the packaging) or listed as "warm white."
- Not all CFLs can be used with dimmer switches. Make sure to check the packaging if you'll need this functionality.
- If you plan to use CFLs outdoors, make sure they are rated for outdoor use. Keep in mind that extreme cold temperatures (more than ten degrees Fahrenheit below zero) may prevent CFLs from operating correcting, and cold temperatures can also prolong the amount of time it takes for a CFL to reach full light output.
- CFLs contain a small amount of mercury, so it's important to recycle them when they're no longer working. You can visit the EPA website for recycling locations.
We hope this helps you to better understand CFLs in general and, more specifically, your choice between spiral-shaped and covered CFL bulbs.