A flickering bulb quickly makes you think the worst. Relax: most of the time, it’s harmless. But one specific scenario deserves a quick call. Here’s how to tell the difference in 30 seconds.
Flickering lights: ghost or real signal?
It’s one of the most-Googled electrical worries — and one of the most misunderstood. The good news: most of the time, a flickering light is harmless (a bulb, a dimmer, a fussy LED). The less good news: in certain specific cases, it’s the number-one symptom of a serious supply fault that deserves a quick call. Here’s how to tell the difference in 30 seconds.
One light, one room, or the whole house?
The first question alone tells you how serious it is.
A single light
Almost always local: a loose or end-of-life bulb, a non-dimmable LED, or a small connection at the fixture. The most harmless.
A whole room
Often at the circuit level: a switch, a junction box or a shared connection. Worth watching.
The whole house
Especially if it flickers when a large appliance starts: the electrical service level. This is the case to take seriously (see below).
The harmless causes (easy to rule out)
An end-of-life or loose bulb
The classic. Tighten it (power off) or replace it. An LED faintly glowing even when off? Often a switch with a night-light or a low-end LED.
An LED on an old dimmer
The flicker duo. Dimmers built for incandescent bulbs handle LEDs poorly — hence flicker and buzz. Fix: an LED-compatible dimmer.
A “non-dimmable” LED bulb
Not all LEDs dim. On a dimmer, a bulb not meant for it flickers. Check for “dimmable” on the box.
A large appliance starting
A brief “dip” when the heat pump, dryer or a motor starts is often normal. It’s when it’s marked and frequent that you dig deeper.
The causes that warrant a look
- A loose connection at a fixture, switch or junction box. The loose contact heats up — a flicker not to ignore.
- An overloaded circuit that “sags” under demand. Common in poorly served kitchens and basements.
- A dimmer or switch that runs warm. If it’s warm to the touch and the light flickers, it’s probably near the end of its life.
- Old aluminum connections poorly terminated, known to loosen and flicker (see our feature on aluminum wiring).
The loose neutral — never ignore it
Only one scenario calls for an immediate call. If you notice several of these signs together, shut off the large appliances and have the electrical service checked quickly.
- The lights across the whole house brighten and dim, sometimes “pulsing.”
- They burn too bright at times (bulbs burning out often), dim at others.
- It coincides with appliances starting, and some outlets work poorly.
- You hear crackling at the service or panel, or smell something hot.
LED + dimmer: making the marriage work
Since we all switched to LEDs, dimmer flicker has become problem number one. The reason is simple: an LED draws very little, and many old dimmers need a minimum load to run cleanly. Below it, they “hunt” — and it flickers. The lasting fix:
- An LED-compatible dimmer (“trailing-edge” technology), not a 2000s-era model.
- Bulbs marked “dimmable,” ideally the same brand/series for all lamps on one dimmer.
- Respect the dimmer’s minimum and maximum load (shown on the packaging).
A flicker that worries you? We settle it fast
A CMEQ-certified company holding an RBQ licence, serving Greater Montreal, Laval, the North Shore, the Laurentians and Lanaudière. We separate the harmless from the serious and, if needed, inspect the electrical service — where a loose neutral can cost you dearly.
Lights flickering for no reason?
We pinpoint the exact cause, from a simple dimmer to a loose neutral. Clear quote.
What people ask us
Why are my lights flickering throughout the house?+
When it’s the whole house — especially if the brightness rises and falls or coincides with appliances starting — the likely cause is at the electrical service, often a loose neutral at the panel or the Hydro connection. It’s a serious fault that can damage your appliances and pose a fire risk: have it checked without delay.
Is a flickering light dangerous?+
Most often, no: an end-of-life bulb, an LED on an old dimmer, or a loose bulb are harmless. It becomes concerning when several lights dim and brighten together, when a switch runs hot, or when you smell burning. Those signs point to a loose connection or a supply problem to fix.
Why does my LED flicker on a dimmer?+
Because many older dimmers were designed for incandescent bulbs and handle an LED’s low draw poorly. You need an LED-compatible (trailing-edge) dimmer and bulbs marked “dimmable,” ideally the same brand. Otherwise the lamp flickers or buzzes.
My lights dim when a big appliance starts — is that normal?+
A brief dim when the heat pump, dryer or a motor starts is often normal, during the inrush of current. It becomes abnormal if the dip is marked, frequent, or repeatedly affects the whole house: then we check the circuit and the electrical service.
What is a loose neutral and why is it serious?+
The neutral is the return wire that balances the voltages in the house. If it loosens, some parts get too much voltage and others too little: bulbs burning out, damaged appliances, overheating. It’s one of the rare flickers that is an emergency and calls for an electrician quickly.
What should I do if a single bulb flickers?+
Cut the power, tighten or replace it, and check that it’s compatible with its fixture or dimmer. If a non-dimmable LED is on a dimmer, replace it with a “dimmable” bulb. If the flicker persists with a new bulb, the connection at the fixture is likely the cause.
Can a dimmer or switch cause flickering?+
Yes. A dimmer incompatible with LEDs, or a worn switch whose contacts loosen, causes flicker and buzz. A switch that’s warm to the touch is near the end of its life and should be replaced. Swapping in a suitable model often fixes it in one go.
How much does it cost to diagnose flickering lights?+
At Groupe Quenneville, a regular visit is $150 travel plus $140/hr (1 hr minimum), and an emergency is $495 plus $255/hr. The diagnosis isolates the cause — bulb, dimmer, connection, circuit or electrical service — and we fix it at the source rather than guessing.
