Where it flickers tells you almost everything
Start by noticing the scope of the flicker — it points straight at the likely cause:
| Scope | Points to |
|---|---|
| One bulb | Bulb, socket, or dimmer compatibility |
| One fixture, any bulb | Fixture socket, driver/ballast, or switch |
| One room / circuit | Loose device connection, overloaded circuit |
| Whole house | Service neutral, panel connections, utility, or large appliance inrush |
| Neighborhood too | Utility transformer or feeder — call the power company |
The ten usual suspects
1. Loose or wrong bulb
Bulb not seated, or a non-dimmable LED on a dimmer — also cheap LEDs with poor drivers.
Fix: Kill power, tighten bulb, check the packaging says “dimmable.” Bend the brass socket tab up slightly if it's flattened.2. Dimmer incompatibility
Legacy leading-edge (TRIAC) dimmers paired with low-wattage LEDs. Most dimmers have a minimum load (typically 20–40W legacy) that 3–4 LEDs never reach.
Fix: LED-rated dimmer matched to the lamp, or add load. Check the manufacturer's compatibility chart.3. Loose connections — the big one
Backstabbed devices, loose wire nuts, loose breaker terminal or panel lug. Flicker here is arcing, and arcing is a fire.
Fix: Re-terminate on the screw terminals, torque breaker and lug connections to spec. Any warm plate, buzzing, or scorch smell is a stop-work-and-call-now item.4. Large appliance inrush
HVAC compressor, well pump, dryer, or welder starting. A brief dip is normal; a noticeable whole-house dim every cycle is not.
Fix: Verify conductor sizing and voltage drop on the branch, check for a soft-start on the compressor, inspect service capacity. Persistent dimming often means an upstream connection problem, not just load.5. Open or loose neutral
Classic signature: half the house dims while the other half brightens, and it shifts with load. This destroys electronics and is a genuine hazard.
Fix: Service call, immediately. We check the service neutral, meter base, panel neutral bar, and any pigtailed neutrals.6. Utility-side issues
Loose service drop, corroded weatherhead splices, failing transformer, tree contact.
Fix: Report to Duke Energy; anything past the weatherhead is the utility's.7. Aluminum branch wiring (roughly 1965–1975)
Oxidation and creep at terminations cause intermittent high-resistance connections.
Fix: AlumiConn or COPALUM pigtailing at every device. Do not just tighten and walk away.8. Failing fixture components
Magnetic ballast at end of life, failed LED driver, corroded can-light socket, heat-degraded recessed fixture.
Fix: Replace driver/ballast or the fixture. LED retrofit kits solve most can-light cases.9. Overloaded or undersized circuit
Long runs, too many devices, 14 AWG doing 12 AWG work.
Fix: Load calculation, dedicated circuits for heavy draws, correct conductor sizing for the run length.10. Damaged conductors
Rodent chew, nail or screw penetration from a remodel, water intrusion in a J-box.
Fix: Isolate the circuit, locate and repair. An AFCI that trips alongside the flicker is a strong tell.Call for service immediately
- Burning or “fishy” plastic smell
- Warm or discolored outlet/switch plates
- Buzzing or sizzling at the panel or a device
- Lights brightening rather than dimming
- Repeated premature bulb failure on the same fixture
- Flicker that started after a storm, a remodel, or a new appliance install
What a homeowner can do
- Tighten the bulb (power off, let it cool)
- Swap in a known-good bulb
- Confirm the dimmable rating
- Note whether it's one fixture or the whole house
- Note whether it correlates with the AC or another appliance starting