In some cases, if consumers want to replace their incandescent bulbs with more energy-efficient lighting sources such as compact fluorescents or LEDs, they may find that their existing dimmer controls will not work.
That is because current dimmer controls are designed to work with incandescent bulbs, and the technology they use is not always compatible with CFLs or LEDs.
According to Kelly Gordon of the Pacific Northwest National Laboratory, normal household dimmers work by turning the power on and off to an incandescent bulb very quickly. Because it happens to fast, most people do not detect that the light is flickering; instead it just looks light the light has been dimmed.
These dramatic spikes in current are fine for incandescents, but Gordon says CFLs and LEDs both require very specific power levels to operate and often the ballasts and drivers that regulate power to the CFL and LED bulbs are not able to withstand the pulsating power.
For example, Gordon says some screw-in CFLs will work with the existing dimmer switches, but often when the lights get down to a 30 percent light level, they will simply shut all of the way off instead of gradually dimming to darkness.
The problems are even worse with LEDs because Gordon says some dimmer switches have a minimum load requirement to work, and when those dimmer switches are hooked up to the extremely energy-efficient LEDs, the dimmers will not work at all. “[Sometimes] they’ll have a 100-watt minimum load that they’ll work on. And LEDs are starting at already way below that, so even if you had a bunch of LED fixtures on it, it still wouldn’t meet the minimum load requirement for the switch, so that’s another challenge,” Gordon explains.
Luckily, CFL manufacturers are now beginning to specify on their packaging whether the bulbs can be used with dimmers. But Gordon says most LED bulb manufacturers have not begun to inform consumers about whether or not their light fixtures are compatible with exisiting dimmers.
In fact, Gordon says she is only aware of one LED manufacturer, Cree LED Lighting Solutions, that specifies which company’s products are compatible with its lights.
“I think, as we see more LED replacement lamps, [or] screw-in lamps, that’s something manufacturers are going to have to do. They’re going to have to give an indication of what kind of dimmer switches their product will work with… They’re going to have to label them as dimmable,” Gordon says.
Over time, as LEDs become more common in residential lighting, Gordon says more LED-compatible dimmer switches will be installed in homes.
“But that’s going to be a long-term thing,” Gordon says. “In the next five years or so there are going to be many of the same issues as with CFLs with dimmer compatibility.”