User Tips for Compact Fluorescent Lightbulbs

Alert Treehugger reader "Jordan" poses such a good question in comment to Friday's article on the benefits of compact fluorescent bulbs, that Treehugger is happy to answer here to help new and old users get the most out of their lighting. Thanks for asking, Jordan.

Jordan asks: Can someone give an explanation on the best way to use CF? I've heard that there's an heathy minimum daily "on time" to keep them long lasting.

Treehugger answers:
Here are some details so you can make good decisions. But don't let all this scare you: just use CF bulbs. They save a lot of hassle replacing bulbs, really do save energy and are cost competitive even with an earlier failure than predicted. For more tips on compact fluorescent bulbs, read on:
The CF bulbs rely on a ballast to cause the gas in the bulb to produce ultraviolet light which in turn causes white phospor on the tube to emit the white light we see. The ballasts wear out before the tubes, so they are the limiting factor in the bulbs' lifespan. Turning the lights on and off will cause the ballasts to fail sooner, reducing the cost advantage of longer life in these more expensive bulbs, and ultimately swinging the balance in favor of power-plant mercury emissions to dead-CF bulb mercury gas disposal (see Friday's article for more on this point). The rule of thumb for optimizing the in-use versus turn-on power is:

  • Standard incandescent: turn off even if you leave the room for just seconds.

  • Compact fluorescent: turn off if you leave the room for 3 minutes.

  • Standard fluorescent: turn off if you leave the room for 15 minutes.

The lifespan rating on your lightbulb is based on 3-hour on/off cycles, so you can expect less life if your average on-time is less than three hours. It is recommended to put compact fluorescent bulbs anyplace where you tend to leave the light on for at least two to three hours at a time. It is OK to simply leave the bulbs "off": that is, there is no minimum daily on-time to keep the bulbs healthy.

CF bulbs can have either an electronic or a magnetic ballast. Electronic ballasts are the most efficient. The electronic ballasts are usually a bit more expensive and turn on instantly, while the magnetic ballasts require a couple seconds to light up. If you are feeding your bulbs with off-grid electricity, the electronic ballast is also superior as it is more tolerant of the modified sine-wave produced by electrical inverters (the device that turns the direct current, for example from a solar panel, into alternating current). Direct current CFs are also available, but harder to find. If you are in doubt, buy just one bulb and try it in your application. Your local store will probably accept the return if you are not satisfied, or you can pass it on to a friend who can use it.

Remember that with CFs, you get more light at lower wattage rating, so if you use a 60-watt incandescent, a 15-watt CF is a good replacement (40W = 9W CF; 100W = 26W CF). For high ceiling lighting, you may need to increase the CF wattage, because CF is more diffuse than incandescent.

Do not use CF bulbs with dimmer switches or in cold locations (less than -10C/14F), unless the manufacture specifically recommends them for these applications.