Why do my LED bulbs flicker or glow when off?

LEDs draw so little power that currents which were irrelevant with filament bulbs are now enough to light them faintly. Most of these symptoms are that, rather than a fault.

Safety

Step by step

1. Separate the two symptoms.Glowing while switched off is a residual current problem. Flickering while on is usually a dimmer or driver problem. They have different causes and different fixes.
2. Check for an illuminated switch.A switch with a small neon or LED indicator passes a tiny current through the circuit to light itself. With a filament bulb that was invisible; with an LED it is enough to make it glow. Replacing the switch with a non-illuminated one solves it.
3. Consider two-way switching.Landing and stairs circuits often run cables in parallel, and capacitance between them induces a small current. It is a normal effect of the wiring rather than a fault.
4. Check whether the switch is in the neutral.In older or badly modified wiring, the switch may break the neutral rather than the live. The bulb is then live all the time, which causes glowing and is genuinely unsafe. That needs an electrician.
5. Fit a bypass or load device for glowing.An LED bypass capacitor fitted across the fitting absorbs the residual current. Inexpensive and effective, and it is the standard fix where the switch cannot be changed.
6. Check dimmer compatibility for flickering.Old dimmers were designed for filament loads and do not work with LEDs. A trailing-edge LED-compatible dimmer is the fix, and it resolves most flickering.
7. Check the minimum load.Dimmers have a minimum wattage. Three 5W LEDs is 15W, which is below many dimmers' minimum, so they flicker or will not turn on. Either a suitable dimmer or more bulbs on the circuit.
8. Match the bulbs to each other.Mixing brands and types on one dimmed circuit causes flickering because their drivers behave differently. Use identical bulbs throughout a dimmed fitting.
9. Suspect the bulb itself.Cheap LEDs have poor drivers and flicker regardless. Swapping one bulb between fittings tells you quickly whether the bulb or the fitting is at fault.
10. Check the connections.A loose connection in a fitting or a ceiling rose causes intermittent flickering. Circuit off at the consumer unit first, then check the terminals are tight.
11. Watch for flickering across several circuits.If lights across the house flicker together, especially when a large appliance starts, that can indicate a loose neutral in the supply. That is an electrician job, promptly.
12. Check for a transformer on low-voltage fittings.Older halogen downlights use transformers that LEDs will not work correctly with. LED downlights usually need the transformer removing or replacing with an LED driver.

Tips

• Glow when off is nearly always an illuminated switch. Swapping it for a plain one is a two-minute fix.
• Flicker when dimmed is nearly always the dimmer. Old dimmers were built for filament loads.
• Swap one bulb between two fittings. It tells you whether it is the bulb or the circuit in thirty seconds.

Common mistakes

• Assuming a glowing LED means a wiring fault — Residual current from an illuminated switch or parallel cables is normal and harmless. It only became visible because LEDs need so little power.
• Using an old dimmer with LED bulbs — It was designed for a filament load and cannot regulate an LED driver, which causes flickering, buzzing and a limited dimming range.

If it doesn't work