Dimming LEDs: why some flicker and how to avoid it
Two components have to agree, and the bulb is only one of them.
What this covers
- Not all LED bulbs dim
- Old dimmers were built for filaments
- Leading and trailing edge
- Minimum load
- Mixing dimmable and non-dimmable
- Buzzing
- Compatibility lists
- Smart bulbs as an alternative
- When to call an electrician
Not all LED bulbs dim
Many efficient LED bulbs are explicitly non-dimmable, and the listing says so. Fitting one to a dimmer circuit causes flicker, buzzing, a limited dimming range or early failure. This is the single most common cause of dimming problems.
Old dimmers were built for filaments
Traditional dimmers were designed for a large resistive load – a filament bulb drawing many watts. An LED bulb draws a fraction of that, which can be below the dimmer minimum load, and the result is flicker or a refusal to switch on.
Leading and trailing edge
Dimmers work by cutting part of the mains waveform, either at the leading or trailing edge. Trailing edge dimmers generally suit LEDs better and run more quietly. If a dimmer is old, it is probably leading edge and probably the problem.
Minimum load
Most dimmers specify a minimum load. Replacing five filament bulbs with five LEDs can drop total load below that threshold, at which point the circuit misbehaves even though every component is nominally correct. Reducing the number of fittings on a dimmer makes this worse, not better.
Mixing dimmable and non-dimmable
Putting one non-dimmable bulb on a dimmed circuit affects the whole circuit, not just that fitting. If a previously working circuit starts flickering after a bulb change, the bulb that was changed is where to look.
Buzzing
Audible buzz usually comes from the dimmer or the driver in the bulb rather than from a fault in either. It is more common at partial dimming levels than at full. Changing to a trailing edge LED-compatible dimmer resolves most cases.
Compatibility lists
Bulb manufacturers publish dimmer compatibility lists and dimmer manufacturers publish bulb lists. Checking one before buying either is dull and considerably faster than diagnosing the problem afterwards.
Smart bulbs as an alternative
A dimmable smart bulb on a plain switch avoids the dimmer question entirely, because the dimming happens inside the bulb. The trade-off is that the wall switch must stay on for the bulb to be controllable, which needs a household agreement.
When to call an electrician
Replacing a bulb is a household task. Replacing a dimmer module is mains wiring, and in most cases the right answer is an electrician. The cost of that is small relative to the cost of getting it wrong.
How this applies when you are buying
Three numbers decide whether a bulb is right. The base code must match the socket. Lumens, not watts, tell you how bright it is. Kelvin tells you the colour: around 2700K is warm, 4000K neutral, 5000K and above is daylight. Mixing colour temperatures in one room is the thing people most often regret.
LED bulbs listed by base type, wattage equivalent, lumen output and colour temperature, in single and multi-packs.
On the shelf at the moment
These come straight from the A & E Bowery Lighting shelf as you read this, not from a list typed when the article was written, so the prices and the availability are current.
- Aipsun Black Modern LED Wall Sconce Hardwired Indoor Wall Lights Set of 2 Up and Down Wall – $6.64
- Energetic 24-Pack A19 LED Light Bulb, 60 Watt Equivalent, Daylight 5000K, E26 Medium Base – $20.49
- TJOY G9 LED Bulb 4W, 6000K Daylight 10 Pack, 40 Watt Eq, G9 Base, 120V – $18.99
Where to go from here
All of the above is the reasoning we use behind the counter at A & E Bowery Lighting when someone asks. If you are weighing up two options and the listing does not settle it, ask: +1 212-219-3888 during opening hours, or service@bowerylights.shop, answered within one business day.
If you order from us
Standard shipping is a flat $11.95 anywhere in the United States, and it is free once the order passes $99. Weekday orders normally leave A & E Bowery Lighting the next working day, with three to seven business days in transit after that. Unopened items can go back within 30 days of delivery. Shipping Policy · Refund and Returns
Related sections of the shop
Related reading
- Base types: E26, GU10, G9 and how to identify yours – The base code is the one specification where being close is the same as being wrong.
- Colour temperature: choosing between 2700K and 5000K – The number that decides whether a room feels comfortable or clinical.
- Lumens, watts and what actually makes a room bright – Wattage equivalence is a rough translation. Lumens is the measurement.
Who wrote this
Written by the team at A & E Bowery Lighting, a lighting, bulbs and fixtures shop at 131 Bowery, New York, NY 10002. The guidance here is what we tell customers across the counter, and it is based on the products we actually stock and the questions we are actually asked. Where we are not certain of something, we say so rather than fill the gap. More about the shop · Contact us
