Lights Flickering? 5 Causes and What You Can Safely Check

You flip the switch and the light stutters, or it dims every time the dryer starts. Most of the time the cause is small: a bulb that is not seated, or an LED that does not suit its dimmer. Now and then a flicker is the first sign of a loose connection, and that one is not a job for an owner.

One question splits the problem in two: is it one light, or many? One fixture points at the bulb or its switch. Several lights on one circuit, or the whole house, point at the wiring or the power coming in, and you will mostly watch and call someone.

Start With These 30-Second Checks

1. 1Count how many lights flicker. One fixture is the bulb or its dimmer. A whole room or the whole house is a bigger job.
2. 2Check whether the flicker happens only when a big appliance starts, like an air conditioner, a dryer or a fridge.
3. 3Sniff near the switch and the fixture. A hot, burnt or fishy smell means stop here and read the safety box above.
4. 4Touch the switch plate and nearby outlet covers with the back of your hand. Warm to the touch is a reason to call an electrician, not to keep investigating.

1. A Loose Bulb

A bulb that has worked slightly loose in its socket loses contact for a split second, and the light flickers. It is a common cause of one flickering fixture.

1. 1Switch the light off at the wall (on a dimmer, a smart switch or a hanging fixture, turn off the breaker too) and wait about 10 minutes, because bulbs stay hot.
2. 2Turn the bulb gently clockwise until it stops. Do not force it. If the glass is cracked, do not use it.
3. 3Switch the light on. If it is steady, you are done.
4. 4If it still flickers, put a bulb you know is good into this socket. If the flicker stops, the old bulb was bad.
5. 5If it flickers with the good bulb too, the socket or the fixture is worn. Stop there and have an electrician look at it.

2. An LED Bulb That Does Not Suit the Dimmer

Old dimmers were built for hot filament bulbs that draw plenty of power. Many LED bulbs draw very little, so an old dimmer cannot control them and the light flickers or buzzes. It is another common cause, and often shows up after you switch to LEDs.

1. 1Switch the light off at the wall (on a dimmer or smart switch, turn off the breaker too) and let the bulb cool before you touch it.
2. 2Read the box or the base of the bulb. A bulb marked dimmable works on a dimmer. One that is not marked dimmable flickers on one.
3. 3Buy a dimmable LED, ideally one the dimmer's maker lists as compatible, and fit it.
4. 4If a dimmable LED still flickers, the dimmer is probably too old. Have an electrician swap it for an LED-rated dimmer. Do not remove the dimmer yourself, because the wires behind it are live unless the breaker is off.
5. 5Set the dimmer to its middle position when you test. Many LEDs flicker at the very low end.

3. A Big Appliance Starting Up

Motors pull a lot of power for a second or two when they start: an air conditioner, a fridge, a dryer, a well pump. On a shared circuit that can dim the lights for a moment. That is usually harmless.

1. 1Note which appliance seems to cause it, and whether it is on the same circuit as the lights.
2. 2A short, mild dim when it starts is common and needs no action.
3. 3If the dimming is strong, happens often, or the bulbs buzz as well, have an electrician check the circuit. Do not unplug or move heavy appliances while they run.
4. 4If a breaker trips as well, read breaker keeps tripping and leave the breaker off if it trips again at once.

4. A Worn Switch or a Loose Connection on One Circuit

If a good bulb in a good socket still flickers, or several lights on one circuit flicker together, a wire may have worked loose at a switch, a fixture or a connector. This is the case where flickering matters most, because a loose connection can get hot.

1. 1Tap the wall switch gently with a finger. If the light flickers when you tap, the switch is worn. Do not remove its cover.
2. 2Look for signs of heat on the switch plate and the fixture: browning, a burnt smell, a warm cover.
3. 3If you see or smell any of that, turn off the breaker for the circuit and call a licensed electrician.
4. 4Do not tighten screws behind a switch or a fixture yourself. The wires there are live unless the breaker is off, and a loose neutral can be dangerous even then.

5. Voltage Problems for the Whole House

If every light in the house flickers or dims, often together with a hum from the panel or other trouble, the cause may sit outside your wiring: the service line, the meter or the utility's equipment.

1. 1Ask a neighbor whether their lights flicker too. If they do, call your electric utility and report it.
2. 2If only your house is affected, call a licensed electrician to check the main connections. Do not open the panel yourself.
3. 3If you see sparks, smell burning at the meter or the panel, or hear loud buzzing, leave the area and call your utility's emergency line. If you see smoke or flames, call 911.

When to Call an Electrician

You can safely check bulbs, dimmers by swapping the bulb, and the pattern of the flicker. Everything inside a wall, a switch, a fixture or the panel belongs to a licensed electrician. HomeAdvisor puts a service call at about $100 to $200 for the first hour; the total depends on what the electrician finds.

1. 1Flickering on several lights or on a whole circuit.
2. 2A flicker that stays after you fit a new, correct bulb.
3. 3Any burning smell, buzzing, crackling, warm switch plates or scorch marks.
4. 4Lights that flicker together with a breaker that trips. Leave the breaker off and call.