Flickering Lights in Hamilton: What Each Pattern Means

By Zvonko Lipovac, Master Electrician, Apollo Electric Inc. · ECRA/ESA 7009372 · Last updated: 2 October 2026

Flickering lights are the most over-ignored electrical symptom in Ontario homes, because the common causes are harmless and the rare one is not. A bulb that stutters when the furnace kicks in is usually nothing. The same stutter arriving with warm switch plates and appliances behaving oddly is a different story entirely, and the gap between the two is a short diagnostic, not a guess.

Apollo Electric Inc. has traced faults across Hamilton, Stoney Creek, Ancaster and Dundas for over 30 years under ECRA/ESA licence 7009372. This page sorts flickering lights by pattern, so you can tell the nuisance from the emergency before you decide how fast to act.

Stop and Call If You See Any of These

Read this section first. If any of it applies, stop reading and make the call.

• A burning or fishy plastic smell anywhere near a switch, outlet or the panel. Switch off that circuit at the breaker if you can reach it safely, and call a licensed electrician immediately. If you can see smoke or scorching, leave the house and call 911 first.
• A switch plate, outlet or panel cover that is warm to the touch. Heat means resistance, and resistance means a connection that is failing.
• Buzzing, crackling or sizzling from a switch, fixture or the panel.
• Scorch marks, discolouration or melted plastic at any device.
• Flickering lights across the entire house at once, particularly if the brightness swings up as well as down.
• A downed power line anywhere near the property. Stay back at least 10 metres, which Alectra describes as the length of a school bus. Call 911, then Alectra at 1-833-253-2872. Never approach it, never move it, never assume it is dead.

None of these wait until morning. Our emergency electrician line in Hamilton is answered 24 hours a day on 905-921-5487. Everything below assumes none of the above is happening.

What the Pattern Is Telling You

Flickering lights sort themselves quickly once you answer three questions. The combination narrows the cause faster than any tool does.

What you see	Most likely cause	How fast
One fixture, all the time	Dimmer and LED mismatch, or a loose connection at that fixture	Routine
One fixture, only when touched or on a windy day	Loose connection at the device or in its box	Soon
One room or circuit	Loose connection at a shared device, often the first outlet in the run	Soon
Whole house, briefly, when a large motor starts	Voltage drop on startup, often normal, sometimes an undersized service	Monitor
Whole house, random, brightness swinging both ways	Loose neutral, house side or utility side	Same day
Whole house, with warm plates or a smell	Failing connection under load	Stop, see above

The single most useful distinction is one circuit versus the whole house. Flickering lights confined to one fixture are almost always a local problem with a local fix. Flickering lights everywhere mean something upstream of every circuit is moving, and the things upstream of every circuit are the service, the panel and the neutral.

What Causes Flickering Lights in a House?

Seven causes account for nearly everything we are called out to, in rough order of how often we find them.

1. A dimmer that does not match the bulb. The most common cause by a wide margin, and the least serious. Covered in its own section below.
2. A loose connection at a device. A terminal screw that was never tightened properly, or back-stabbed wiring that has relaxed over years of heating and cooling. This is the second most common cause and it is the one that eventually gets hot.
3. A failing bulb or a loose lamp holder. Worth ruling out in ten seconds before anything else, and it explains more flickering lights than people expect.
4. Voltage drop when a large motor starts. A furnace, a well pump, an air conditioner or a table saw pulls hard for a moment. A brief dip is physics. A deep, long dip on an older service is a capacity signal.
5. An overloaded or undersized circuit. Common where a kitchen or a basement has been renovated onto circuits that were never meant to carry it.
6. A loose neutral. Uncommon, and the reason this page exists. Its own section below.
7. A utility side fault. Outside your house and not your electrician's to fix, but easy to identify, also below.

Notice what is not on that list: ghosts, old houses being old, and anything you should learn to live with. Flickering lights always have a physical cause, and every one of these seven is findable.

The Loose Neutral, and Why It Is the Dangerous One

This is the one cause of flickering lights worth understanding in detail, because it is what justifies the urgency in the first section.

A standard Ontario home takes two 120 volt legs plus a neutral. The neutral is the shared return path, and it is what keeps both legs balanced at 120 volts. When that neutral connection goes loose or corroded, the two legs stop sharing properly. One side rises above 120 volts while the other falls below it, and the split moves as loads switch on and off around the house.

That produces a very specific signature. Lights in one part of the house dim while lights in another part get brighter, and the pattern changes when a large appliance cycles. It is not a steady flicker. It is a seesaw.

Why it matters: the over-voltage side can damage electronics and appliances outright, and the loose connection itself heats under load, which is how it becomes a fire. This is also why flickering lights that come with warm cover plates are never a wait-and-see problem.

A loose neutral can sit in the panel, at the main lugs, at the meter base or on the utility side of the connection. Finding which is a measurement job, not a visual one, and it is the point at which the diagnosis belongs to a licensed electrical contractor. The same kinds of fault surface as partial power loss across half a house, so if you have seen both symptoms, say so when you call.

When It Is Just the Dimmer and the LED

Now the good news, because this accounts for most flickering lights we are called about.

LED bulbs draw a fraction of what incandescent bulbs drew, and many dimmers installed before LEDs were common need a minimum load to regulate properly. Below that load the dimmer cannot hold a steady output, so the bulb stutters, buzzes, glows faintly when off, or refuses to go low without flickering.

Three things to check, in order:

1. Is the bulb marked dimmable? A non-dimmable LED on a dimmer will flicker, and no amount of rewiring fixes that.
2. Is the dimmer rated for LED? An older incandescent dimmer with LED bulbs is the classic mismatch. An LED-rated dimmer usually resolves it outright.
3. Are the bulbs mixed? Different brands and batches on one dimmer behave unpredictably together. Matching them often settles it.

If swapping to a known dimmable bulb on a known LED-rated dimmer clears the flicker, you are done and it was never a safety issue. If flickering lights persist after that, the dimmer was a red herring and the problem is in the wiring behind it.

House Side or Utility Side

You can usually place flickering lights on one side or the other yourself in about a minute, and it decides who you call.

• Ask a neighbour. If the houses either side are flickering too, it is the supply, not your wiring.
• Look at the street lighting on the same stretch during the episode.
• Check whether it tracks your own appliances. Flicker that lines up with your furnace or air conditioner cycling is almost certainly inside your house.

If it is the supply, the Hamilton distributor is Alectra Utilities, covering Hamilton, Dundas, Ancaster, Stoney Creek and Waterdown. Report it on 1-833-253-2872, Option 1, answered 24 hours a day. Alectra is responsible up to and including its connection at your property. Everything past that point is your equipment and an electrician's work.

If it is inside the house, it is ours. A proper diagnosis measures voltage on both legs under load rather than swapping parts and hoping, and the same method applies whether the symptom is flicker or protection that keeps operating.

Hamilton Housing and Why This Comes Up Here

Hamilton produces more flickering lights calls than its size suggests, for reasons built into the housing stock.

The pre-war lower city, Corktown, Strathcona, the North End and Durand, carries original wiring layered with decades of additions, and loose connections accumulate at every junction somebody added along the way. Much of the Mountain went up in the post war decades on sixty and one hundred amp services that now run air conditioning, a second fridge and a home office, so voltage drop on startup is routine. East Hamilton and Stoney Creek add 1960s and 70s aluminum branch wiring, where the connection at each device is exactly where trouble starts.

On top of that, service equipment on the Escarpment face and in older neighbourhoods has weathered decades of freeze and thaw, and a neutral connection that corrodes slowly gives you flickering lights long before it gives you anything more dramatic. That warning is the useful part. It is worth acting on.

If the pattern you are seeing sits anywhere in the same-day column of the table above, get in touch or call 905-921-5487. If you want to check who you are hiring first, we set out the licence checks worth doing, and you can read more on our electrical safety page.

Frequently Asked Questions

Are flickering lights dangerous?

Usually not, but sometimes very. A single fixture flickering on a dimmer is a nuisance. Flickering across the whole house, brightness swinging up as well as down, or any flicker accompanied by warm switch plates, buzzing or a burning smell, points at a failing connection that heats under load. That is a same-day call, not a wait-and-see.

Why do my lights flicker when the furnace or air conditioner starts?

Large motors draw heavily for a moment as they start, which pulls voltage down briefly across the house. A short dip is normal physics. A deep or long dip, especially on an older sixty or one hundred amp service, suggests the service is close to its limit and worth having assessed.

Can a loose neutral cause flickering lights?

Yes, and it is the most serious common cause. A loose neutral lets the two 120 volt legs fall out of balance, so lights in one part of the house dim while lights elsewhere brighten, with the pattern shifting as appliances cycle. It can damage electronics and the loose connection heats under load, so it needs a licensed electrician promptly.

Why do my LED lights flicker on a dimmer?

LEDs draw far less current than the incandescent bulbs older dimmers were designed for, and below a dimmer's minimum load it cannot hold a steady output. Check that the bulb is marked dimmable, that the dimmer is rated for LED, and that all bulbs on the circuit are the same brand and batch. That fixes most cases.

Should I call Alectra or an electrician about flickering lights?

Call Alectra on 1-833-253-2872 if your neighbours or the street lighting are affected too, because that points at the supply. Call a licensed electrical contractor if the flicker is confined to your property or tracks your own appliances. Alectra is responsible up to its connection at your property; everything past that is your equipment.

Does Apollo Electric diagnose flickering lights in Hamilton?

Yes. Apollo Electric Inc. is a Licensed Electrical Contractor under ECRA/ESA licence 7009372, serving Hamilton, Stoney Creek, Ancaster, Dundas, Waterdown and the surrounding area. We measure both legs under load rather than swapping parts, and the line on 905-921-5487 is answered 24 hours a day.

References

• Alectra Utilities, report an outage, Hamilton's distributor, its 24 hour line and the 10 metre stay-back distance.
• Electrical Safety Authority, Ontario's electrical safety regulator.
• Electrical Safety Authority, hiring an electrician or contractor, on why only a Licensed Electrical Contractor may be hired.
• Electrical Safety Authority contractor locator tool, for verifying an ECRA/ESA licence.
• CSA Group, on certification marks to look for on bulbs, dimmers and fixtures.