You switched to LED bulbs, and now the dining room lights flicker at low settings, buzz, or snap off before they reach the bottom of the dimmer. It is one of the most common lighting complaints we hear, and in most cases nothing is wrong with the wiring. The bulbs and the dimmer simply do not get along.
Why LEDs and dimmers clash
Most wall dimmers in homes were designed for incandescent bulbs, which are simple resistive loads. LED bulbs have a small power supply, called a driver, inside the base, and every driver responds to a dimmer differently. A U.S. Department of Energy report on dimming LEDs with phase-cut dimmers found that problems are often a matter of compatibility between the LED source and the dimmer rather than a fault in the LED itself, and that compatibility between a specific bulb and a specific dimmer is often unknown in advance.
The usual symptoms and what they mean
- Flicker or shimmer at low settings. The dimmer and driver are not agreeing at the bottom of the range. Often fixed by adjusting the dimmer's low-end trim, if it has one, or by a compatible dimmer.
- Lights snap off before the dimmer is at the bottom. Same cause; the low-end setting is below what the bulbs can follow.
- Flicker at every setting, or lights that will not turn fully off. Common when a dimmer made for incandescent bulbs controls only a few LEDs. The same DOE report notes that older phase-control equipment typically expected a minimum load of around 40 watts, far more than a few LED bulbs draw.
- Buzzing from the bulbs or the dimmer. Often a mismatch too, or bulbs not designed for dimming.
- One bulb flickers, the rest are fine. Usually that bulb. Try swapping it.
- Flicker that comes and goes even at full brightness, or other lights flickering too. That points away from the dimmer; see lights flickering throughout the house.
What fixes it
- Dimmable bulbs. Check that every bulb on the dimmer is marked dimmable. One non-dimmable bulb can cause trouble for the whole group.
- Matching bulbs. Use the same brand and model on one dimmer. Mixed drivers respond differently.
- A compatible dimmer. The DOE report recommends choosing combinations that the LED or dimmer manufacturer has tested together, and dimmers that meet the NEMA SSL 7A standard with compatible bulbs. Many dimmer makers publish compatibility lists.
- Adjust the low end. Many LED-rated dimmers have a small trim adjustment that sets the lowest level. Raising it often stops flicker at the bottom.
- A neutral-wire dimmer. Some modern dimmers and smart dimmers work better with a neutral connection; older switch boxes may not have one, which is something we check.
When it is not the dimmer
If the dimmer is warm, hot or discolored, or you hear crackling from the switch box, turn it off and have it checked; see warm outlets and switches. If recessed lights go off and come back on after a while, that is usually heat, not the dimmer; see recessed lights turning off by themselves.
What we do
We check the bulbs, the dimmer type and its rating, the load on it, and the box wiring. Then we recommend the simplest fix: matching bulbs, a compatible dimmer, or a trim adjustment. Where the lights are recessed, an LED retrofit made for that fixture often fixes both the flicker and the heat. Our lighting repair page covers dimmers and switches.
Questions people ask
Is LED flicker on a dimmer dangerous?
Usually not; it is a compatibility issue. But a dimmer that is hot, buzzing loudly or discolored is overloaded or failing and should be replaced.
Do I need to replace all my dimmers when I switch to LED?
Not always. Try matched, dimmable bulbs first. Replace the dimmers that still flicker or will not dim smoothly.
Smart dimmers and switches
Smart dimmers add a second variable: they need a little power for themselves even when the lights are off, and some draw it through the bulbs, which can make LEDs glow faintly or flicker when they should be off. Models that use a neutral wire avoid that. Before buying one, check that the switch box has a neutral, and check the maker's list of compatible bulbs. If you are replacing several dimmers, test one with your actual bulbs before buying the rest.
Choosing bulbs that dim well
Look for bulbs marked dimmable, and where possible ones the bulb maker lists as tested with your dimmer. Buy enough of one model for the whole fixture or room, since the same wattage from a different maker can behave differently on the same dimmer. Keep a spare or two; a replacement from a different batch years later may not match.
Why do my lights flicker only when the dimmer is at full brightness?
That is less typical of a compatibility problem. Check for a loose bulb, a failing bulb, or a loose connection at the dimmer or fixture.
Need it looked at?
KRW Electric (EC13012832) troubleshoots and repairs flickering and buzzing LED lights and dimmers in Pinecrest, Coconut Grove, South Miami and Miami Beach, with same-day service when scheduling permits. Call (305) 359-7312 and tell us what you are seeing. We will ask a few questions, tell you whether it sounds urgent, and give you the earliest time we have. Our before you call checklist covers what to have ready, and what happens on a repair visit explains the rest.
Reviewed by Kyle White, KRW Electric Company LLC — licensed electrical contractor EC13012832.
