Dimmable compact fluorescent bulb
Controlling lighting levels with CFLs
Dimmable compact fluorescent bulbs are one way to get better control of the lighting levels in a room, while still benefiting from the energy saving characteristics of compact fluorescent lights or CFLs.
You should not use standard compact fluorescent lights on a standard dimmer switch. While doing this may work for some time, standard dimmer switches will cause standard CFLs to burn out faster and there is a risk that the ballast could catch fire. The more often you run the CFLs at below 100% power, the shorter their lives will become and the greater the risks of fire. Even if you always run your standard CFLs at 100% power on a standard dimmer switch, the risk of fire is still significant as the bulbs still draw up to 3 times as much current as when on a standard simple switch.
Compact fluorescents are cost effective for two reasons: low power consumption, and long life. Since using a standard CFL on a standard dimmer switch will shorten the bulb's life, even setting aside the fire risks, you may not get enough hours of use from the bulb for the energy savings to make up for the higher up front cost and shortened bulb life. And your savings will go up in smoke (literally) if a fire starts as a result of using a standard dimmer with standard CFLs.
You have two choices when using CFLs with a dimmer:
- Buy dimmable compact fluorescent bulbs. These bulbs are specially designed to work with a standard dimmer switch such as the dimmer switches used for incandescent or halogen bulbs.
- Use regular CFLs and install a dimmer switch for fluorescent lights. These switches are more expensive than standard dimmer switches, but since regular CFLs are cheaper than dimmable compact fluorescent bulbs, and you can use standard CFLs with this type of dimmer switch, you may save money overall.
If you are wanting to use a dimmer switch because you want to save energy, bear in mind that a CFL bulb uses about one quarter the energy of a standard incandescent or halogen bulb. By switching from incandescent or halogen to CFLs you will be saving enough energy that adding a dimmer switch won't make that much difference. You can use my CFL savings calculator to figure this out, but with slightly different inputs. Let's start by assuming you have regular CFLs at 23 watts, you already have a free standard dimmer switch available, and want to switch to dimmable CFLs on that dimmer switch to save energy. Here's what you could enter:
- Wattage of the regular CFL (for example 23 watts) as the 'incandescent' wattage
- Wattage of the dimmed CFL (for example, 12 watts - about 50% dimmed) as the 'CFL' wattage
- Cost per regular CFL - put this in the 'incandescent bulb' cost - enter $0 because you already own the bulbs
- Cost per dimmable CFL - put this in the 'CFL bulb' cost - about $3.25 (only slightly more than a standard bulb)
- Enter the same 8,000 hour life for both bulbs
Assuming $0.10 per kilowatt hour electricity cost, and two hours of use per day, a single light bulb pays for itself in 6.41 years - not a very good payback period. If your motive is only to save more energy, upgrading from standard CFLs and a regular switch to dimmable CFLs and a standard dimmer switch doesn't make economic sense. You would be far better to invest that extra money in other energy efficiency upgrades in your home.
The same holds true for buying a fluorescent dimmer switch - you'll save a lot by switching from incandescent to standard fluorescent lights, but if you already own a standard dimmer switch, the upgrade to the fluorescent dimmer switch needs to be factored in. While these switches used to cost upwards of $40, so that they would eat up most or all of the savings you realize from switching from incandescent lights CFLs, more economical versions are now available in the $15-20 range, such as the one shown at left.
My own recommendation is to go with dimmable compact fluorescents on a standard dimmer switch - since most people already have the dimmer switch, a standard dimmer switch is relatively inexpensive, and the price difference between a standard CFL and dimmable compact fluorescent bulb is minimal.
Note that the main risk when using standard CFLs with standard dimmer switches is when the switch is not at 100% power - reducing the power level actually increases the risk of fire. While trying to keep the power always at 100% or off will reduce the risk it will not eliminate it. Therefore my recommendation is NEVER us a standard dimmer switch with standard CFLs.
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