Why do my LED bulbs flicker on a dimmer switch?

LED bulbs flicker on a dimmer most often because the bulb and the dimmer do not suit each other. The bulb may not be a dimmable model, the dimmer may have been made for old incandescent bulbs, or its lowest setting may be below what the bulb can handle. Those are fixable with the right parts. Flicker that comes with heat, a smell or other symptoms is a different problem, and it belongs with a licensed electrician.

Why LEDs are fussier on a dimmer

Incandescent bulbs make light with a filament and dim without hesitation; LED bulbs make light with a semiconductor, and the dimming dynamics are different.^[1] When the two are mismatched, Leviton lists the glitches you see: noise such as buzzing or humming, flickering, strobing or flashing, popping on or dropping out, a poor or limited dimming range, and ghosting, where the light glows after it is turned off.^[1]

ENERGY STAR's summary is short: "Not every LED light works well with every dimmer switch."^[3]

The usual causes

The bulbs are not dimmable. Many LED bulbs are not made for dimmers at all. Leviton's first rule is "Use only LED bulbs labeled as “DIMMABLE”".^[1]

The dimmer was made for incandescent bulbs. Leviton's second rule: "Be certain the dimmer switch is rated to dim LED bulbs (older models may not be)".^[1] A dimmer that has been on the wall since the house had incandescent bulbs is a common suspect.

The pair is not on the compatibility list. Dimmable bulbs and LED-rated dimmers still vary. If you are keeping an existing dimmer, ENERGY STAR advises checking the dimmer manufacturer's website to see which bulbs they recommend.^[3] For recessed lights, ENERGY STAR's rules say certified downlights sold as dimmable must list compatible dimmers on the package, or give a web address for them, along with known incompatibilities with dimmers, sensors and timers.^[4]

The low end is set too low. ENERGY STAR requires that certified downlights marketed as dimmable must dim continuously from 100% to at least 20% of their light output.^[4] Leviton's guidance is that "Setting the minimum light level helps ensure smoother dimming if you encounter any flickering"^[1] and Leviton's LED dimmers have a mode selector switch to change the minimum and maximum light levels.^[2] The dimmer's instruction sheet says whether yours has one.

What you can check without opening anything

Start with the paperwork, not the wall. Read the bulb base or box for the word dimmable. Find the dimmer's brand and model from its box or instruction sheet, or ask the electrician to read it. Then look the pair up on the dimmer maker's compatibility list.

Note the pattern, because it tells an electrician a lot:

• Flicker only at the low end of the slider usually points to the minimum-level setting or the pairing.
• Flicker at full brightness, on lights controlled by an ordinary switch, or across several rooms makes a dimmer mismatch a less likely explanation.

If the pair is not compatible, the fix is parts, not a repair. If you don't find a good match with your current dimmer, ENERGY STAR's advice is to consider replacing it, or to return the lights and try a different one.^[3] Changing bulbs is a bulb change. Changing the dimmer is electrical work at the switch box.

When flicker is a wiring warning

Flicker is not always the dimmer. The CPSC's guidance on older home wiring puts it this way: "Signs of electrical system problems include hot-to-the touch face plates on receptacles or switches; flickering lights; circuits that don’t work; or the smell of burning plastic at outlets or switches."^[6] Its advice is plain: "If you notice any signs of a problem, have a qualified electrician determine the cause."^[6]

Some warmth at a dimmer is expected. The CPSC's home safety checklist notes that "Some dimmer switches may warm during normal use."^[7] But unusually warm outlets or switches may indicate an unsafe wiring condition, such as a loose electrical connection that can start a fire.^[7] Hot is not warm. Our answer on warning signs of bad wiring covers the other symptoms.

Permits and who does the work

Virginia's building code treats a dimmer swap as an ordinary repair: replacement of dimmer and control switches needs no permit application in Groups R-3, R-4 and R-5, and in Group R-2 where serving a single dwelling unit.^[8] No permit is not the same as no licence. In Virginia, no individual may engage in, or offer to engage in, work as a tradesman unless licensed,^[9] so anyone you pay to change the dimmer needs an electrical licence or a licensed electrician supervising. See whether you need an electrician to install a light fixture for the details.

When to call a licensed pro

Call a licensed electrician when:

• A switch plate or dimmer is hot to the touch, or you smell burning plastic.
• Lights flicker at full brightness, on ordinary switches, or in several rooms.
• Flicker started after other electrical work, or comes with breakers tripping or dead outlets.
• The dimmer needs replacing with a compatible LED-rated model, or its minimum level needs adjusting.
• Recessed fixtures with built-in LEDs flicker. Some LED light fixtures have LEDs built in as a permanent light source,^[5] so there is no bulb to swap.

Ask the electrician to bring a dimmer listed as compatible with your bulbs or fixtures. If you are planning new lights, our answer on adding recessed lighting covers choosing fixtures and dimmers together.

Find an electrician

Browse lighting installers on Loclis, look up electricians in Blacksburg, or read more electrical answers.

Describe your flickering lights and licensed local electricians quote the repair.