Title 24 JA10 Low-Flicker Requirements, Explained

There are two moments when JA10 suddenly matters: a submittal comes back rejected, or an inspector asks whether the dimmer and the fixture were tested together, and nobody on the job can answer.

JA10 is not a requirement. It is a test method. That distinction is the whole reason it confuses people, and it is also the reason a fixture can be perfectly compliant on its own and still fail once you put a particular dimmer in front of it.

Here is what the appendix actually says, what the number has to be, and what to check before you order.

JA10 is a measurement procedure, not a performance limit

Joint Appendix JA10 of California's Title 24, Part 6 is titled "Test Method for Measuring Flicker of Lighting Systems and Reporting Requirements." Its own introduction describes its job plainly: it quantifies flicker from lighting systems and processes that signal to express flicker as a percent amplitude modulation below a given cut off frequency.

That is all JA10 does. It tells a laboratory how to measure. The pass or fail threshold lives somewhere else. Worth knowing before you go looking: JA8 is the part of the code that points at JA10 by name. Section 110.9, which covers dimmers, states the same numeric limit without naming a test method. That is not a figure of speech. Search the adopted 2025 Standards document and the string JA10 does not appear in it once, while flicker appears exactly once, in Section 110.9(b)3B. The same is true of the 2022 Standards. The test method lives in the appendices; the Standards only carry the number.

The threshold: reduced flicker operation

Two separate parts of the code carry the actual limit, and both land on the same number.

For light sources. JA8.4.6 sets the dimming, flicker and audible noise requirements a light source must meet to qualify as high luminous efficacy. Its flicker clause requires that a light source in combination with a specified control provide reduced flicker operation when tested at full light output as specified in JA10, where reduced flicker operation is defined as having percent amplitude modulation, that is percent flicker, less than 30 percent at frequencies less than 200 Hz. The same clause requires the source to be retested and shown compliant at 20 percent light output. (2025 Reference Appendices, Appendix JA8, Section JA8.4.6(c) and (e).)

For dimmers. Section 110.9(b)3 covers controls that provide dimming functionality. Subsection B requires that a dimmer provide reduced flicker operation, meaning that directly controlled light sources shall be provided electrical power such that the light output has an amplitude modulation of less than 30 percent for frequencies less than 200 Hz without causing premature lamp failure. (2025 Building Energy Efficiency Standards, Section 110.9(b)3B. The 2022 Standards carry this subsection in identical wording.)

So the number is the same on both sides of the wire: under 30 percent amplitude modulation, below 200 Hz. What differs is who has to demonstrate it, and how. JA8 ties its requirement to the JA10 test method explicitly. Section 110.9(b)3B states the limit and stops there, so a dimmer manufacturer is not directed by that section to produce a JA10 report.

What percent amplitude modulation means

JA10 defines it with a single equation. Percent amplitude modulation equals the maximum recorded light level minus the minimum, divided by the maximum plus the minimum, times 100.

A lamp whose output never varies reads zero. A lamp that swings fully from peak to dark reads 100. Neither JA8.4.6 nor JA10 states a rationale for where the 30 percent and 200 Hz limits were set, so treat them as the thresholds the code specifies rather than as a described design intent.

How the JA10 test is actually run

The appendix is specific, and reading it explains why casual bench measurements do not count.

  • Enclosure. The test enclosure admits no stray light, and holds 25 degrees C plus or minus 5 degrees C.
  • Sensor. A photodetector with a rise time of 10 microseconds or less, feeding a transimpedance amplifier and an oscilloscope, or an equivalent system of the same accuracy.
  • Sampling. Data recorded at intervals no greater than 50 microseconds, which is a rate of no less than 20 kHz, capturing at least one second of output.
  • Supply. Rated primary voltage and frequency held within 0.5 percent, sinusoidal, with voltage total harmonic distortion no greater than 3 percent.
  • Stabilization. Output is stabilized before each reading, and is treated as stable when consecutive one minute readings deviate by no more than 0.5 percent.
  • Dimming points. Measurements are taken within 2 percent of three settings: 100 percent, 20 percent, and the minimum dimming level claimed by the manufacturer. Where a system cannot dim below 20 percent, the measurement is taken at its minimum instead.

Then the calculation. Percent amplitude modulation is computed on the raw unfiltered trace. The data is transformed into the frequency domain by Fourier analysis, filtered five separate ways at cutoffs of 40, 90, 200, 400 and 1,000 Hz (JA10 introduces this as four additional conditions and then lists five, so do not be thrown when the code text and the report disagree on the count), transformed back, and the percent amplitude modulation is recalculated for each filtered set.

That is why a JA10 report has more than one flicker number in it: a filtered result at each cut off frequency, at each required dimming level, alongside the unfiltered figures. The 200 Hz result at 100 percent and at 20 percent light output is the one the compliance threshold points at.

Results go to the California Energy Commission in the reporting format specified in JA10, and the submitting party has to keep the supporting documentation, including the raw photometric data file, for two years from the date of certification and produce copies within 10 days of a written request.

The part that catches people: results are combination specific

This is the clause worth reading twice, because it is where field surprises come from.

JA10 states that its results are specific to each combination tested. A light source with a representative dimmer. A low voltage lamp with a representative transformer and dimmer. A source with a driver and a dimming control. Change a component and you are outside the tested combination.

The appendix then draws a sharp line between control types:

  • Phase cut dimming. For non incandescent sources, a flicker measurement represents only that specific combination of phase cut dimmer, ballast or driver, and lamp. The results cannot be applied to other combinations. Incandescent gets two carve-outs of its own: a phase cut dimmer tested against a line voltage incandescent lamp is representative for that dimmer with any line voltage incandescent lamp, and a phase cut dimmer tested with a transformer for low voltage incandescent lamps is representative only for that combination of dimmer and transformer, with any incandescent lamp. On low voltage incandescent work that second rule is the one that bites: the dimmer and the transformer are the tested unit, so swapping the transformer voids the result. Low voltage LED loads are not incandescent, so they fall under the stricter no-transfer rule instead.
  • 0-10V, digital, wireless and powerline carrier. The measurement is specific to that combination of control type, ballast or driver, and lamp, but the lamp and driver result can be applied to other systems using another control of the same type providing the signal.

Read practically: a 0-10V result travels reasonably well across 0-10V controls. A phase cut result does not travel at all for non incandescent sources. The two incandescent provisions run the other way, and they are not equally generous: line voltage incandescent transfers across lamps for that dimmer, while low voltage incandescent locks the dimmer and transformer together as a pair, though that pair then carries with any incandescent lamp. That is the technical reason a fixture and a wall dimmer that each look fine on paper can still produce visible flicker when paired, and why substituting "an equivalent dimmer" late in a job is a real risk rather than a paperwork detail. If you want the background on the control types themselves, see our guide to 0-10V dimming and how it compares to ELV, MLV and phase control.

JA8 is a residential requirement, and that matters

Before the list below: JA8 sets qualification requirements for high luminous efficacy light sources installed to comply with Section 150.0(k), the residential lighting section, with multifamily handled in its own section. It is not a general nonresidential requirement. Section 110.9, by contrast, is mandatory code-wide. If you are specifying a commercial job, the dimmer requirement is the one that reaches you; the JA8 list is context.

Where flicker sits in the wider JA8 list

JA8 compliance is not only about flicker. The same JA8.4 section that carries the flicker clause also requires, per the adopted 2025 Reference Appendices:

  • Luminous efficacy at or above the applicable state or federal appliance standard, or 45 lumens per watt, whichever is higher, at full light output.
  • Power factor of 0.90 or greater at full light output.
  • Start time no greater than 0.5 seconds.
  • CRI of 90 or higher with an R9 value of 50 or higher, for sources not covered by the Title 20 CRI rules, and a nominal CCT capability of 4000 K or less.
  • Dimmability down to 10 percent light output.
  • Compliance with NEMA SSL 7A for LED sources designed to be dimmed by forward phase cut dimmers.
  • Audible noise no greater than 24 dBA measured at one meter at full light output.

Flicker and audible noise both get retested at 20 percent output. Our JA8 high efficacy lighting guide covers the certification and marking side in full.

What Section 110.9(b)3 asks of a dimmer beyond flicker

If you are selecting a dimmer for a California job, the flicker clause is one of four. Section 110.9(b)3 of the 2025 Standards also requires that a dimming control:

  • Reduce lighting power consumption by a minimum of 65 percent at its lowest setting.
  • Provide an offsetting that produces a zero lumen output.
  • For wall box dimmers and associated switches designed for three way circuits, be capable of turning lights off, and on to the level set by the dimmer if the lights are off.

A dimmer that clears the flicker bar and misses any of these is still not compliant. Our Title 24 lighting controls compliance guide walks the rest of the controls requirements.

How to check a product before you commit

  1. Confirm the source carries a JA8 marking, not just a manufacturer claim of low flicker. JA8 certified products are certified to the Energy Commission and marked.
  2. Ask for the flicker data at 20 percent, not only at full output. JA8.4.6 requires the source to be retested and shown compliant at 20 percent light output, so a full-output-only report is incomplete on its face.
  3. Ask which control the source was tested with. For phase cut, this is the whole ballgame, because the result does not transfer.
  4. Match the control type to the driver. JA10 treats 0-10V, digital, wireless and powerline carrier control alike: the lamp and driver result transfers to another control of the same type. Phase cut results do not transfer for non incandescent sources. Where a phase cut dimmer feeds a transformer for low voltage incandescent lamps, the dimmer and transformer are the tested pair, so specify them together; low voltage LED does not transfer at all.
  5. Do not substitute the dimmer late. An equivalent by wattage and voltage is not equivalent by flicker.

If a submittal has already come back short, or you are staring at a schedule with a dimmer callout you are not confident in, send us the takeoff and we will match it. Rock Lighting and Electric stocks the dimmers and drivers side of this problem, so the pairing gets checked before it ships rather than after. Browse dimmers and the wider lighting controls range, or talk to us directly if the job is unusual.

Contractors buying regularly should open a contractor account for project pricing.

Which edition applies to your job

The 2025 edition of Title 24, Part 6 took effect on 1 January 2026, and every requirement quoted above is read from the adopted 2025 documents: the 2025 Building Energy Efficiency Standards for Section 110.9, and the 2025 Reference Appendices for JA8 and JA10.

For the flicker requirement specifically, the two editions land in the same place. Section 110.9(b)3B carries identical wording in the 2022 and 2025 Standards, and in both documents the string JA10 appears nowhere at all while flicker appears exactly once, in that subsection. So if your permit was pulled under the 2022 cycle, the under 30 percent below 200 Hz threshold and the dimmer clause read the same.

What did change between the editions is the residential exemption structure, not the flicker number. See the outdoor LED question below. Your compliance documentation still has to cite the edition your permit was pulled under.

Related guides

FAQ

What is JA10 in Title 24?
JA10 is Joint Appendix 10 of California's Title 24, Part 6, titled "Test Method for Measuring Flicker of Lighting Systems and Reporting Requirements." It is a laboratory test procedure, not a performance limit. It defines how flicker is measured and expressed as percent amplitude modulation below a given cut off frequency. The pass or fail threshold comes from elsewhere in the code: JA8.4.6 for light sources, which points at JA10 by name, and Section 110.9(b)3B for dimmers, which states the same numeric limit without naming a test method.
What is the Title 24 flicker limit?
Two sections carry the same number. JA8.4.6 requires a light source, in combination with a specified control, to show percent amplitude modulation of less than 30 percent at frequencies less than 200 Hz when tested per JA10, at full light output and again at 20 percent. Section 110.9(b)3B requires a dimmer to provide reduced flicker operation, worded as amplitude modulation of less than 30 percent for frequencies less than 200 Hz without causing premature lamp failure, and does not name a test method. The wording here is quoted from the adopted 2025 code text, and Section 110.9(b)3B reads identically in the 2022 edition.
How is percent amplitude modulation calculated?
JA10 defines it as the maximum recorded light level minus the minimum, divided by the maximum plus the minimum, multiplied by 100. A steady source reads zero and a source that swings fully from peak to dark reads 100. The calculation is performed on the unfiltered trace and again on the data after filtering at 40, 90, 200, 400 and 1,000 Hz cut offs.
Does a JA10 flicker result apply to any dimmer I pair with the fixture?
Usually no. JA10 says results are specific to the combination tested. For non incandescent sources on a phase cut dimmer, the result represents only that exact combination of dimmer, ballast or driver and lamp, and cannot be applied to other combinations. For 0-10V, digital, wireless and powerline carrier control, the lamp and driver result can be applied to other systems using another control of the same type. Incandescent is the exception: a phase cut dimmer tested on a line voltage incandescent lamp carries to any line voltage incandescent lamp, and a phase cut dimmer tested with a transformer for low voltage incandescent lamps carries only as that dimmer and transformer pair, though within that pair it carries with any incandescent lamp. Low voltage LED loads are not incandescent and do not transfer at all.
At what dimming levels does JA10 require measurement?
Within 2 percent of three settings: 100 percent of full light output, 20 percent, and the minimum dimming level claimed by the manufacturer. Where a system's minimum light output is above 20 percent of full output, the measurement is taken at that minimum instead of at 20 percent.
Does JA8 apply to commercial projects?
JA8 sets the qualification requirements for high luminous efficacy light sources installed to comply with Section 150.0(k), which is residential, with multifamily addressed in its own section. It is not a blanket nonresidential requirement. Section 110.9(b)3, the dimmer requirement, is mandatory across the code and does reach commercial work.
Do outdoor LED light sources have to meet JA8 and the flicker requirement?
Two separate answers, and on the JA8 side the edition matters. On JA8: LED light sources installed outdoors are exempt, so the JA8.4.6 reduced flicker operation requirement does not attach to them. Under the 2025 code that exemption is Exception 4 to Section 150.0(k)1A, item i, and it is unqualified. Under the 2022 code the same exemption sat in Table 150.0-A, where it was qualified: the exempt column applied to light sources other than those installed in ceiling recessed downlight luminaires, and item 7 of the facing column pulled all recessed downlight sources back into JA8. So an outdoor soffit or eave downlight was caught by that carve-back under 2022, and the 2025 restructure did not carry it forward. Read the exemption in the edition your permit falls under rather than from a summary. On the dimmer: Section 110.9(b)3B applies to dimming controls in its own right, code-wide, regardless of whether the source being controlled is exempt from JA8. So an exempt source on a dimmer still sits behind a control that owes reduced flicker operation.

Sources

This article is general guidance, not a substitute for the manufacturer’s current documentation or the adopted code for your project. Confirm specifications, compatibility, and code requirements for your specific application before purchase or installation.

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