Which bulbs are good for AC dimming?

Bulb suitability for AC dimming

Normally professional LED luminaires adjust the brightness of the light through variations on the secondary side of the LED driver (transformer). For hotel rooms, decorative lights like pendants, desk lights and wall mounted reading lights, however often use bulb sockets more common in domestic use, such as E14, E27 or GU10. These bulbs do not require an external driver, but rather accept common 230V AC mains power. The ‘driver’ is a small transformer built into the bulb itself.

Whether or not LED bulbs can be dimmed by adjusting the AC power available to them, depends on the manufacturers’ choices on how this driver is built. Not all LED bulbs are designed to be dimmed at all. Do not use a non-dimmable with a dimmer.

Different dimmable LED light bulbs also react differently to the trailing edge phase cut dimming. The goal of this document is to provide an easy reference to selecting the right bulb.

There might be differences in linearity, upper and lower brighness limits, and dimming speed. We have optimized the dimming behaviour and compared different manufacturer light bulbs to provide insight which bulbs work the best with our AC dimming.

Rating Scale

Rating Explanation
★★★★★ Great, dims very nicely withou problems throughout the range. Lower limit is very dim, and full power is achieved.
★★★★ Very good, dimming is nice and linear, limitations may be present in dimming range in the low end
★★★ Good, works well with the dimmer, but minor issues with linearity or range
★★ Not recommended, works with the dimmer, but dimming might be highly unlinear or have issues with the scale
Poor, do not use. Dimming behavior differs from other bulbs and cant be used well with universal dimmer, flickering may be present on some dimming levels.

Bulb ratings

Bulb Base Model Number Compatibility rating
Philips halogen 28W E27   ★★★★★
Clas Ohlson 3W E27 36-6846 ★★★★
Clas Ohlson 9.5W E27 36-6848 ★★★★
Airam 75 12W Cool white E27 A7GAGS ★★★
Airam 60 8.5W Cool white E27 A7ALBG ★★★
Airam 60 8.5W Warm white E27 A7GABN ★★★
Airam PRO LED 6W Pure white E14 A7PRBC ★★
Airam 35 3.6W spot Warm white E14 A7LEEO ★★
Philips warm glow 60W Clear Warm white E27 9290020190 ★★★
Philips warm glow 60W Smoky E27 9290020534 ★★
Phillips 3.8W 50 spot GU10 9290020657 ★★
Osram 7W Smoky E27 SST CLAS A 60 FR 7 W/4000K E27 ★★
Osram 8.5W clear E27 SST CLAS A 75 FIL 8.5 W/2700K E27 ★★
Osram 5.9W spot E27 SST R63 60 36° 5.9 W/2700K E27

These results are based on our own research in the attempt to provide as universally compatible dimmer as possible. Compatibility of bulbs not included here is difficult to predict as bulb driver characteristics may differ even between models of a single manufacturer. If you are interested in using another bulb in your project, let your Mount Kelvin representative know, send us 3 pcs of the bulb in question, and we will run tests for you.