Dimmable LED filament bulbs: what dimmable means, which dimmers, and what to test
Choose a dimmable bulb by the combination you will install: the exact bulb, dimmer, supply voltage and bulb count. Agree how low it must dim, how it must start and what light-output measurements the project needs. A dimmable entry on a bulb table is the starting point for that check.
What measurements answer a flicker question?
The U.S. Department of Energy's Flicker Basics distinguishes temporal light modulation, the changing light-output waveform, from the artifacts an observer experiences. It also explains why the LED driver and its response to a dimmer matter. This is public research guidance, not a product pass/fail standard or a test result for these bulbs.
| Check | What to record | Decision it supports |
|---|---|---|
| Visual and phone-video screening | Bulb and dimmer identity, bulb count, supply, dimmer setting and camera settings; note bands, visible flicker or uneven dimming. | Use observations to identify settings for further investigation. Do not record a clean-looking clip as a measured flicker pass. |
| Defined light-output measurement | Ask the test provider for the instrument, method, metric, operating conditions and results at the agreed settings. | Compare like-for-like results against the project's stated criteria. DOE's research explanation treats the waveform and the observer's response separately; a camera observation alone does not supply that measurement. |
| Exact combination acceptance | Approve the current bulb version with the intended dimmer model, supply voltage, minimum and maximum bulb counts, and any mixed load. | Repeat the starting and dimming checks below on that combination. Keep its acceptance record with the order; do not extend it to another dimmer or bulb version. |
For an EU order, distinguish legal requirements from the project's dimming checks. Regulation (EU) 2019/2020, Annex II uses PstLM for flicker and SVM for the stroboscopic effect at full load for in-scope mains LED and OLED light sources. The 2021/341 amendment includes the SVM change applying from 1 September 2024. These are EU ecodesign provisions with product definitions and exemptions; have the test provider confirm applicability and the current limits for the exact light source. Full-load results do not establish performance throughout a dimmed installation, and neither a phone video nor this regulatory reference establishes conformity of an iLamp Technology bulb.
Dimmable entries in the bulb table
Of the 74 bulb specifications on the LED filament bulbs page, 69 print Dimmable: Yes. A tested-dimmer entry appears on 66 of those, and every one of them names the Lutron Diva DVELV-300P / DVCL-153P entry, a factory statement on 2015–2020 data. These historical entries are not proof of compatibility with your dimmer, so test the exact current bulb and dimmer combination before ordering.
What the bulb table prints
Four printed fields in each bulb table decide a dimming question.
| Field | What is printed | How to read it |
|---|---|---|
| Dimmable | Yes on 69 models, No on two, absent on three | Read it per model, never per shape. The two models printed as not dimmable are an A60/A19 milky bulb and an S14 bulb. |
| Dimmer tested | On 66 models, every one naming the Lutron Diva DVELV-300P / DVCL-153P | One dimmer, named by the factory. It is not a compatibility list and not a conformity document. |
| Power factor | On 31 models: >0.8 on 20 of them, >0.85 on 11 | Ask for it when many bulbs sit on one circuit, or where your market asks for the figure. Where a table prints none, ask with your quotation. |
| CRI | On all 74 models: >80, >90, or ">80 or 90" where both grades are listed | Colour rendering, not dimming. Check the colour of the sample low on the dial as well as at full output. |
Forward-phase and reverse-phase dimmers
General guidance, not a statement about any model. A mains wall dimmer cuts part of every half-cycle of the supply. Forward-phase types, usually triac-based and sold for incandescent and halogen loads, cut the start of the half-cycle. Reverse-phase types, often described as trailing-edge or electronic, cut the end of it and are usually easier on the small driver built into a filament bulb. The historical factory entry names DVELV-300P and DVCL-153P; check each dimmer's own instructions and the current bulb compatibility data.
Check the load range in the dimmer's instructions. A few low-wattage filament bulbs on one dimmer can draw less than that minimum, and a dimmer under its minimum load can flicker, buzz or refuse to start. These symptoms need investigation for the actual bulb and dimmer combination. That is why the bulb count belongs in the sample test and not only in the order.
What changes the answer
| Variable | Why it changes the result | What to do |
|---|---|---|
| Dimmer type | Forward-phase and reverse-phase dimmers drive the bulb's driver differently. | Find out which type your installer or your customer will fit, and test that type. |
| Minimum load | A dimmer states its own minimum load; a small number of low-wattage bulbs can fall below it. | Read the dimmer's instructions, then test with the bulb count you will actually sell. |
| Bulb count and mixed loads | A filament bulb sharing a dimmer with other lamp types changes the load the dimmer sees. | Test the circuit as it will be built, not a single bulb on a bench. |
| Mains band | Only 13 of the models print a voltage entry; those that do print AC110-130V / 220-240V, or one band on its own. The dimmer and the bulb have to be built for the same band. | Have the mains band of the sample and of the production order written on your quotation. |
| The model itself | Dimmable is printed per model, and three tables print no dimmable entry at all. | Quote the ILT reference and the factory code, and read that model's own table before you order. |
Which bulbs this covers
The shapes with a dimmable entry run across C35, C32, C22, C7, A60/A19, ST64, ST58, ST45, G45, G80, G95, G125, T30, T20/T25/T45, P45, spiral filament and G4 / G9, on E26/E27, E12/E14, B22, B15, G9 and G4 bases. Shape does not decide the answer: two models print Dimmable: No and three print no dimmable entry, so the model table is the only place to read it. The factory's own descriptions offer many of these shapes in dimmable and non-dimmable versions, so name the version you want on the enquiry. The bulb shapes guide explains how the shape codes read.
Five sample tests
Run all five with the dimmer you will sell into, not with a bench supply. Write the results into your acceptance note so the same checks can be repeated on the production batch.
Dim to the bottom
Test at the lowest output setting your application requires, within the dimmer's instructions. Note the point where the bulb drops out, jumps or goes dark, and whether it comes back cleanly when you raise it.
Look for flicker
Observe the bulb at full output and low on the dial. If you record phone video or slow motion, keep the camera settings with it and flag bands or stutter for investigation. Use the measurement method above for a defined pass/fail decision; a clip alone is screening, not a flicker measurement.
Listen for buzz
In a quiet room, listen at the bulb and at the dimmer through the whole range. A buzz that appears only in part of the range usually points at the pairing of dimmer and load.
Start from cold
Switch on at the lowest setting from cold. Note any delay, any jump to full output, and any bulb that will not start until the dial is raised. Repeat after an hour of warm-up.
Test the real circuit
Repeat the first four checks with the number of bulbs, the mix of lamp types and the dimmer of the actual installation. Minimum load is a property of the circuit, not of one bulb.
Documents for dimmable bulbs
Ask for the current UL listing card for the exact bulb model. A tested-dimmer specification is not a conformity document. Shenzhen iLamp Technology Co., Ltd also appears in Intertek's ETL Listed directory under UL 1993 and CSA C22.2 No. 1993 for self-ballasted LED lamps; your quotation states which of the bulb models fall under that listing. For CE and RoHS there are dated certificate copies, and you can request the current declaration of conformity and supporting reports for your exact model and market. The documents and certification register sets out the dated records and documents to request for each family and market, and the CE and energy labels guide explains which EU and UK rules decide the paperwork.
Bulb and dimmer compatibility
Test the exact current bulb, dimmer and load together on your sample before ordering. The factory's named dimmer entry speaks only to that dimmer, not to other dimmers, models or markets. The printed figures are 2015–2020 data, so your quotation states the current model, its power factor and its dimmable entry before you order.
For a current Lutron dimmer, use Lutron's own LED Compatibility Tool to search the exact dimmer and bulb model. A result there describes Lutron's testing for that listed pairing; it does not establish that an iLamp Technology model is the same bulb or compatible. Match the exact codes first, then verify the production sample in the real circuit.
Questions buyers ask
Does dimmable mean the bulb will dim on my dimmer?
Which dimmer did the factory test?
Why does a dimmer flicker or buzz with only two or three bulbs on it?
Can I order the same shape in a non-dimmable version?
Ask for a dimmable sample
Send the shape, the base, the mains band and the dimmer you will sell into. The quotation names the exact factory code and configuration, a sample follows, and your acceptance checks decide whether the order runs. The samples and ordering page sets out the full sequence.
Ask for a quotation on WhatsApp Telegram: t.me/ryanfulfil
Notes
Bulb figures: filament-bulb specifications are the factory's 2015–2020 listing; the current model and its figures are confirmed on your quotation.
Documents: which of the bulb models fall under the UL 1993 / CSA C22.2 No. 1993 listing is confirmed on your quotation. Historical copies do not establish current coverage for your order.