The Answer
The Short Answer
LEDs react far faster than incandescent bulbs, so small power fluctuations become visible as shimmer, pulsing, or strobing. Some flicker is a quality problem inside the bulb's driver; some is caused by a dimmer designed for old filament bulbs. Occasional flicker when an appliance starts may be circuit voltage drop. Constant flicker, buzzing, heat, or flicker on multiple fixtures should be treated as an electrical issue.
The Full Explanation
Dimmer Mismatch Is the Usual Cause
Many older dimmers were designed around incandescent loads that used far more power. Put a low-wattage LED on the same dimmer and the electronics may not have enough load to operate cleanly, causing flicker at low levels. Use bulbs explicitly marked dimmable, pair them with LED-compatible trailing-edge dimmers, and check the dimmer's minimum and maximum load range.
Cheap Drivers and Low-Quality Bulbs
Inside every LED bulb is a driver that converts mains power into the low-voltage current LEDs need. Better drivers smooth that current; cheap ones often do not. This is why two bulbs with the same lumens and colour temperature can behave very differently. If one bulb flickers in several fixtures while another does not, replace the bulb with a higher-quality model.
When to Call an Electrician
Call an electrician if flicker affects several circuits, appears with non-dimmable switches, comes with buzzing or burning smells, or happens when large appliances start. Loose neutral connections and overloaded circuits are not lighting quirks. For a single fixture, first test a known-good bulb and remove the dimmer from the equation if possible.
Related Questions
Sources
- 1LED Lighting
U.S. Department of Energy
- 2Light Bulbs
ENERGY STAR
- 3Dimming CFLs and LEDs
Lutron