Why Do LED Bulbs Flicker and How to Fix It

You switch on the light and the room seems to "shimmer": bulbs flicker, your eyes get tired, and when you film the room with your phone, stripes run across the screen. Sound familiar? Flicker is one of the most common LED lighting complaints – yet the culprit is far from always the bulb itself. In this article we go through all the main causes, from a cheap power supply to faulty electrical installation, and explain what to check first. We draw on expert findings from the Lithuanian national broadcaster LRT programme "Vartotojų kontrolė" (Consumer Control) and on our own electrical installation practice.

Why do LED bulbs flicker?

The four most common causes are: a poor-quality power supply (driver) inside the bulb, faulty or incorrectly wired electrical installation, powerful appliances operating nearby and an incompatible dimmer. The LED itself cannot flicker on its own – it merely reproduces whatever the supply circuit feeds it, so the root cause is almost always found around the diode, not in it.

A poor power supply is the most common culprit

An LED is a passive component: it needs smooth direct current, which the driver built into the bulb produces from the mains alternating current. In cheap bulbs this is exactly where corners are cut: filtering components are missing, so the light pulses at mains frequency. In the LRT programme's experiment, a physics expert identified roughly 50 Hz flicker from the recorded footage – pulsing at that rate is genuinely perceptible and unpleasant: it feels dizzying and strains the eyes.

The fewer filters a bulb has, the more easily it is also disturbed from outside – for instance by a powerful appliance running nearby. That is why two identical-looking bulbs can behave completely differently in two different homes.

Can a phone camera test bulb quality?

No – that is a myth. The popular internet "tests" that judge bulb quality by filming it with a phone have no basis. The rolling bars you see on camera are often just a beat-frequency effect: if the fixture pulses at 50 Hz and the camera records at 25 frames per second, "beats" appear on screen – stripes your eye never sees in reality.

Experts stress that even a perfectly good bulb can show artefacts on camera if the camera and bulb frequencies happen to coincide. And vice versa – the human eye stops perceiving pulsation above roughly 24 frames per second even where a camera still registers it. Reliable flicker measurements are only made in a laboratory, which is also why proving to a seller that your bulbs pulse more than normal is unfortunately difficult. Your best protection is choosing reputable manufacturers – see our LED bulb buying guide for how to recognise them.

LED bulbs dying every few months? Check the installation

If LED bulbs in your home last only a month or two, the bulb is almost certainly not to blame. The most common cause is voltage surges – brief spikes in the mains that gradually destroy the bulb's electronics. Simply switching brands will not fix it.

A pattern like this is a serious signal that the home's electrical installation is in poor condition: badly joined wires, weak contacts, inadequate surge protection. At that point it is no longer just about bulbs – the same surges wear out your other electronics, and poor contacts are a fire risk. Our advice is not to wait: call in a qualified electrician to assess the installation and fit appropriate surge protection, so the cause is fixed rather than the symptom.

Flickering lights: what to check, step by step

1. Narrow the problem down. Is one bulb flickering, or several in different rooms? One bulb – most likely its own driver; several – look for a shared cause in the wiring.
2. Move the bulb to another fixture. If the flicker travels with the bulb, the bulb is at fault. If it stays with the fixture – suspect the switch, the wiring or the dimmer.
3. Check the dimmer. A non-dimmable LED bulb on a dimmer will flicker. The dimmer must also be rated for LED loads – old dimmers designed for incandescent bulbs are often incompatible.
4. Note when it flickers. If it coincides with powerful appliances switching on (heater, kettle, air conditioner), suspect load or contact problems in the installation.
5. If bulbs are also short-lived – stop experimenting and call an electrician: the installation and surge protection need to be inspected.

Frequently asked questions

Is a flickering LED bulb harmful?

Perceptible flicker is tiring: eyes ache or fatigue, dizziness is possible, productivity drops. Spending long hours in such a room is not something to put up with – fix the cause rather than get used to it.

Why does the bulb glow faintly even when switched off?

Usually because of an illuminated switch, induced leakage in long cable runs, or a switch that breaks the neutral rather than the live wire. It is an installation issue an electrician can resolve quickly.

Can I return a flickering bulb to the seller?

If the bulb is genuinely defective – yes, the warranty applies. But proving excessive flicker with household means is hard, since reliable measurements require a laboratory. That is why it is worth asking the seller to test the bulb in a live socket before you buy.

Summary

A flickering LED bulb is a symptom whose cause may hide in the bulb's driver, in the dimmer, or in the home's electrical installation. Replace a single flickering bulb with a better one – but if several flicker, or bulbs keep dying every few months, it is time to call in a qualified electrician: the cause usually lies in the installation, not the bulbs.

Looking for reliable, flicker-free LED bulbs? Browse our LED bulb range or get in touch: we will help you choose quality light sources and a dimmer that matches them.

Source: LRT programme "Vartotojų kontrolė" – commentary by physical technology experts on LED flicker, supplemented with practical recommendations from our specialists.