A slight flicker in the lights when the AC turns on, or a TV screen that "shimmers" for a moment — these are common symptoms of voltage fluctuation, a phenomenon with understandable causes, some inside your home and some entirely outside it.
What is voltage fluctuation?
Ideal home voltage is nearly constant (such as 230 volts). Voltage fluctuation means a temporary deviation from this value — a rise (surge/swell) or a drop (sag/dip) — lasting a short period, anywhere from a fraction of a second to several seconds.
Causes inside the home
- Suddenly turning on a high-power appliance (AC unit, washing machine, water pump): the motors in these appliances draw a very high starting current for a moment when switched on, causing a temporary voltage drop on the rest of the shared circuit — this is why lights flicker briefly when the AC turns on.
- Loose or deteriorated connections in the distribution panel or connection points: these increase resistance at those points, causing a larger voltage drop across them when current increases.
Causes outside the home
- Fluctuations in the public grid: changes in the total load on the transformer feeding your area (especially during peak hours), or switching operations on the network.
- Faults or maintenance on nearby distribution lines, which may cause temporary fluctuations before the grid stabilizes.
- Weather phenomena (storms, nearby lightning) which can cause very short, sharp voltage surges.
Effect on sensitive appliances
Appliances containing sensitive electronic circuits (computers, TVs, network equipment) are more susceptible to sharp voltage fluctuations (surges) — these can cause unexpected restarts, or in repeated severe cases, shorten the lifespan of their internal components. Simple motor- and heating-based appliances are relatively less sensitive to brief fluctuations.
For sensitive and expensive devices (computers, home medical equipment, network systems), surge protectors and voltage stabilizers/AVRs are available that connect between the outlet and the device, reducing or absorbing these fluctuations before they reach the appliance. If fluctuations are frequent and noticeable in your home (constant light flickering, for example), it's worth having an electrician inspect to distinguish between an internal cause (connections) and an external one (the public grid).
Sample answer: Internal causes include suddenly turning on high-power appliances (AC unit, water pump), where their motors draw a high starting current that causes a temporary voltage drop on the rest of the home's circuits, or loose connections in the distribution panel that increase resistance. External causes include public grid load fluctuations during peak hours, maintenance work or faults on nearby distribution lines, or weather phenomena such as nearby lightning.
Treating every light flicker or voltage fluctuation as "a public grid fault that nothing can be done about," without checking possible internal causes such as loose connections in the distribution panel, which may be locally resolvable with a simple electrician inspection.
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