By Emmanuel Sauvage · Updated
Technical guide
Dimmable LEDs and dimmers
A non-dimmable LED on a dimmer can flicker, buzz or fail early. A dimmable LED on an old dimmer may do the same. Both sides must match.
Three checks
- The bulb says "dimmable" on the box and the datasheet.
- The dimmer suits LEDs. Old incandescent dimmers are usually leading-edge (TRIAC) with a minimum load of 40–60 W; three 5 W LEDs (15 W) sit below that and flicker. LED-rated dimmers are mostly trailing-edge and accept loads from a few watts.
- Load within limits. Manufacturers often derate: a dimmer rated 400 W for incandescent may be limited to around 10 % of that for LEDs. Use the LED rating printed on the dimmer, not the incandescent one.
UK specifics
Dimmer manufacturers (Varilight, MK, Hamilton, etc.) publish LED compatibility lists by bulb model. Replacing a light switch with a dimmer on the same circuit is not notifiable under Part P outside bathroom zones, but it must comply with BS 7671; switch off at the consumer unit and test dead first. If unsure, use a registered electrician.
US specifics
Look for dimmers marked CL (CFL/LED, e.g. Lutron Diva CL) or compatible with NEMA SSL 7A phase-cut dimming. Turn off the breaker before working; local codes based on the NEC apply and some jurisdictions require a permit.
Symptoms and fixes
| Symptom | Likely cause | Fix |
|---|---|---|
| Flicker at low level | Below dimmer minimum load | Trailing-edge LED dimmer, or set its low-end trim |
| Buzzing | Leading-edge dimmer with LED driver | Trailing-edge dimmer |
| Glow when off | Leakage current via dimmer/smart switch | Dimmer with neutral, or bypass/load correction device |
| Doesn't dim below 50 % | Incompatible pair | Check the dimmer's compatibility list |
UK · GU10 230 V
Philips CorePro LED GU10 4W, 4000K, dimmable (10-pack)
Listing: 50 W halogen replacement, 350 lm, 36° beam, CRI 80, dimmable with compatible dimmers, energy class F.
Check price on Amazon UKUS · E26 120 V
Philips Ultra Definition LED A19, 8W, 2700K (8-pack)
Listing: 60 W equivalent, 800 lm, E26 base, dimmable, flicker-free. Listed as CRI 95.
Check price on Amazon USProduct data below is taken from the manufacturer's listing on Amazon, checked on 22 October 2026. Prices change: check the current price before buying. As an Amazon Associate I earn from qualifying purchases.