Why do my lights flicker when the furnace or fridge starts?

An electric motor needs several times its running current for the first fraction of a second as it gets up to speed. That surge, called inrush current, pulls the voltage down slightly on the wires it shares. Old incandescent bulbs barely showed it; LED bulbs, and especially dimmable LEDs on dimmer switches, can be more sensitive, so a house that never flickered can start after a bulb change. In October, the furnace blower starting many times a night is when people first notice.

Is it normal for lights to dim when the furnace turns on?

A slight, brief dip in a few lights when the furnace blower or the fridge starts is common and usually harmless. It tends to be strongest in lights on the same circuit as the motor, or close to the panel on the same leg of the service. If the dip is small, lasts under a second and has not changed in years, most electricians would call it normal. If it is new, getting worse, or happens across the house, the Electrical Safety Authority (ESA) lists dim, surging or flickering lights as a possible sign of a loose connection in a circuit, a fixture or the service, and advises calling a licensed electrical contractor.

Which lights flicker, and how? Narrow it down

Why do my lights get brighter, not just dimmer?

Lights that get brighter in one part of the house while others dim are the clearest sign that something is wrong with the neutral, the return wire that keeps the two halves of a home's 240-volt service balanced. When the neutral connection at the panel, the meter base or the overhead service wires loosens, the voltage on each half can swing up and down with the load. That can burn out bulbs and damage electronics, and a loose connection heats up. It is not something to watch for a few weeks. Call an electrician, and if the problem seems to be at the meter or the wires coming to the house, call your distributor, because that part is theirs.

Is it my wiring or the hydro company?

Ask a neighbour first. If their lights flicker at the same moments, or it happens in storms or high wind, the cause is probably on the utility side, and it is the distributor's to investigate. Toronto Hydro asks customers to report flickering lights or partial power online or at 416-542-8000 (press 1), and to report brief momentary outages only if they keep happening. If the flicker follows your own appliances, is limited to your house, or is worse in one room, the cause is almost always inside, from the meter in, and that needs a licensed electrician.

In Toronto and York Region homes, who do I call?

• Your electricity distributor depends on the town: Toronto Hydro across the City of Toronto, including North York; Alectra Utilities in Vaughan, Richmond Hill, Markham and Aurora; NT Power (Newmarket-Tay Power Distribution) in Newmarket. Both councils approved selling NT Power to Alectra in March 2026; NT Power keeps operating until the sale closes.
• Electrical permits do not come from the town in Ontario. The licensed electrical contractor files the work with ESA, which inspects it. Ask your electrician for the ESA notification number.
• Older houses: 58% of the City of Toronto's homes were built before 1981, and about 30% of Newmarket's (Statistics Canada, 2021 Census). Older panels, splices and service wires have had more years to loosen, so new or worsening flicker in an older house deserves a look sooner.
• If the electrician finds the service is too small for the house and recommends an upgrade, the distributor handles the disconnect and reconnect, requested through its own service-request process.

What to tell the pro

• Which lights flicker: one fixture, one room, one floor, or the whole house, and whether some get brighter.
• What triggers it: the furnace blower, the fridge, the microwave, the dryer, or nothing in particular.
• How long it lasts, and whether it is new, the same for years, or getting worse.
• Whether the bulbs are LED and on dimmers, and whether neighbours see it too.
• Anything warm, buzzing, discoloured or smelling of burning, and any breaker that has tripped.
• The house's age, the panel's amperage (on the main breaker), and a photo of the panel label.

What does an electrician cost on Doyo?

On Doyo, a Panel Inspection is $246.40, all-in with Doyo's fee included, and is the usual first visit when flicker affects the whole house or several rooms. A single fixture that flickers is Light Fixture, $224.20. Electricians on Doyo work under an ECRA/ESA Licensed Electrical Contractor licence, checked by Doyo and kept current, and you can look the licence up on ESA's site.