EZSMART Corporation, ESA/ECRA #7012690 , North York , Ontario
Mon-Fri 08:00 AM - 05:00 PM
The fridge kicks on and your kitchen lights dim for a second. The dryer starts and every bulb in the basement drops brightness. A slight, momentary dim on very heavy motor startups is normal, but if your lights are dimming when an appliance turns on regularly, especially in rooms far from the appliance, you have a real electrical problem worth diagnosing.
A motor drawing startup current temporarily pulls the voltage down on whatever it shares a supply with. On a healthy service, this happens for a fraction of a second and only in the immediate room. When the dim is deep, long, or house-wide, one of three things is wrong: your utility service is undersized or has a loose connection at the meter, a main lug or breaker in your panel is loose or corroded, or the appliance is on a circuit sharing wire with lighting when it should be on a dedicated circuit.
Level one: a barely perceptible flicker in the same room only, less than half a second. This is normal and needs no action. Level two: a noticeable dim of one or two lights in the same room lasting one to two seconds. Usually a shared circuit issue — move the appliance to a different circuit or add a dedicated line. Level three: lights across the whole house dim visibly whenever a major appliance starts. This points to a service-side fault, most often an open or loose neutral, and it is dangerous — it can push over-voltage into some circuits and under-voltage into others. Book professional light-flicker diagnosis right away.
Homes with original aluminum branch wiring or a 60- or 100-amp service from the 1970s see much more dimming than modern 200-amp copper installations. Every aluminum-to-copper splice adds resistance, and every corroded meter or main-lug connection makes voltage sag worse under load. A pre-purchase electrical inspection on any GTA home built before 1985 should specifically test voltage sag under simulated load — a step most home inspectors skip.
Toronto Hydro will also come out and check the supply side for free if you suspect the sag is coming from their service drop or transformer. Ask specifically for a voltage recording over 24 hours — a snapshot reading will miss the fault, but a full-day recording captures every sag as your appliances cycle on and off.
If your lights only dim when the furnace or heat pump starts, put an amp clamp on the appliance’s feed and watch the inrush number. A properly-sized soft-start kit can cut that inrush by 60 to 70% for a couple hundred dollars — often much cheaper than the panel upgrade you were quoted for. It is an underused fix.
Do not live with dimming lights — some causes are dangerous. Call 416-838-9006 or visit our contact page and we will diagnose it the same day.
Brief voltage drop from motor start current. Slight dimming is often normal; sustained dimming is not.
Only if it lasts more than a second or if voltage is chronically low.
Move loads to different circuits, upgrade wiring gauge, or address utility-side voltage.
Yes. Frequent voltage swings shorten bulb life, especially incandescent.
If dimming affects the whole house and multiple neighbours, it is a utility issue.
Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp
