The Core Problem: LEDs Draw Very Little Power
Traditional incandescent dimmers were designed around resistive incandescent filaments, which draw significant, steady current across their full range. LED bulbs are different: they run on internal electronic drivers that convert AC power to the low-voltage current the LED chip needs, and they draw a fraction of the wattage an equivalent incandescent bulb did - often 6-10W where an incandescent drew 40-60W. Many older or basic dimmers have a minimum load requirement, commonly 40W or more, that a single LED bulb simply cannot reach, which is one of the most common causes of flicker, buzzing, or a light that will not dim below a certain point.
Common Causes, Roughly Ranked by Likelihood
1. The dimmer is not rated for LED bulbs. If you kept an old incandescent-only dimmer after switching to LED bulbs, this is very likely the issue. LED-specific or universal dimmers use electronic circuitry designed for low-wattage loads.
2. The bulb is not labeled dimmable. Non-dimmable LED bulbs are common and cheaper, but they are not designed to run on any dimmer - flicker, buzzing, or reduced lifespan is expected, not a defect.
3. The bulb brand or model is not on the dimmer's compatibility list. Even LED-rated dimmers are tested against specific bulb models. Mixing bulb brands on the same dimmer, or using a bulb the manufacturer has not tested, is a frequent cause of flicker that otherwise looks like a hardware fault. Check your dimmer manufacturer's published compatibility list against the exact bulb you are using.
4. Total load is under the dimmer's minimum wattage. A dimmer rated for a 250W maximum might also specify a 10W or 25W minimum. A single 8W LED bulb on that dimmer can flicker simply because there is not enough load for the dimmer's circuitry to read correctly. Adding a second bulb, or switching to a dimmer with a lower minimum, resolves this.
5. Loose wiring or a failing dimmer. If flicker happens across every bulb type, including incandescent, or gets worse when you jiggle the switch, that points to a wiring or hardware problem rather than a bulb-and-dimmer mismatch. Turn off power at the breaker and have a licensed electrician inspect the connection.
6. A dimming-technology mismatch. LED dimmers generally use either leading-edge or trailing-edge (electronic low-voltage) dimming. Some LED drivers perform noticeably better with one type than the other; if you have already confirmed compatibility and load and still see flicker, trying the other dimming technology, per the manufacturer's compatibility notes, can help.
How to Fix It
Start with the two free checks: confirm the bulb packaging says dimmable, and confirm your specific bulb model appears on your dimmer's published compatibility list. If either check fails, that is your answer. If both check out and flicker persists, the next step is usually replacing the dimmer with one explicitly designed and tested for LED loads - most major electrical brands sell an LED-specific or universal dimmer line for exactly this reason. If flicker appears on multiple circuits or worsens over time, have a licensed electrician check for a loose neutral or other wiring issue before replacing more hardware.
