Why Do My Lights Flicker When an Appliance Turns On?

A brief flicker when a large appliance like an air conditioner or oven starts up is usually normal, caused by a short voltage dip as the appliance draws its initial surge of current. Frequent flickering, or flickering that happens across the whole house, points to a loose connection or an overloaded circuit worth having checked.

The normal version: brief flicker on appliance startup

Large appliances draw a brief surge of current when they first switch on, well above their normal running draw. This causes a momentary voltage dip on that circuit, which can show up as a quick flicker in nearby lights. If it's brief, only happens with specific large appliances, and the lights return to normal immediately, this is a known and generally harmless characteristic of how these appliances work.

The version that isn't normal

Flickering that happens across the whole house rather than just nearby lights, flickering that persists rather than being a brief flash, or flickering that's become more frequent or noticeable over time are different. These patterns point to something at the switchboard or in the wiring itself, most commonly a loose neutral connection, rather than a normal characteristic of appliance startup.

Why this can point to a switchboard issue

A loose neutral connection at the switchboard can cause voltage to fluctuate unevenly across circuits, which shows up as flickering that isn't tied to one specific appliance. This is more than a lighting annoyance, uneven voltage can also affect and potentially damage other appliances and electronics in the home over time, which is why whole-house flickering is worth having assessed rather than living with. It's also worth checking whether the flickering coincides with anything else happening on the property, since ruling out an obvious external trigger helps narrow down whether the cause is genuinely internal to your own switchboard or wiring.

What we check on site

We start by testing voltage at the switchboard under normal conditions and then again while the appliance in question is running, to see exactly how much the voltage actually dips and whether it's within a normal range. We also check the physical connections at the board itself, since a loose neutral often shows visible signs, discolouration or looseness, once the board's opened up properly.

When it's worth getting checked versus when it's not

A brief, consistent flicker tied to one specific large appliance starting up is generally not something to worry about. Flickering that's spreading beyond that pattern, getting worse over time, happening with no obvious trigger, or accompanied by any other switchboard symptom like buzzing or warmth, is worth a proper assessment. When in doubt, it costs nothing to ask. If your board is showing other symptoms too, see our 7 warning signs guide.