Commercial guideUpdated July 20269 min read
Does your building need arc flash labels?
Two separate rulebooks decide this, and they have different trigger conditions. One of them stopped applying the day your equipment was installed. The other one applies every day there is someone working on it. Most of the confusion on this topic comes from answering the first and assuming it settled the second.
Two rulebooks, not one
When a building owner asks whether they need arc flash labels, they are usually asking one question. There are two, they come from different places, and they behave differently.
The California Electrical Code is an installation code. It decides what has to be marked, and it applies when equipment is installed or altered. Like every installation code, it does not reach backwards. Equipment that was correct when it went in does not become incorrect because a newer edition was published.
Cal/OSHA is an employer duty. It decides what has to be known about the hazard and how people are protected from it. It applies every day there is someone working on or near that equipment, and it has nothing to say about when the equipment was installed, because that was never the point.
NFPA 70E is neither of those. It is a consensus standard, not California law on its own. It is the recognized method for carrying out the assessment Cal/OSHA requires, which is why everyone refers to it and why it is easy to mistake for a regulation.
The trap is straightforward once you can see it. An owner asks whether they are grandfathered, gets an accurate yes from the first rulebook, and concludes there is nothing to do. The second rulebook never grandfathered anything, because it was never about the installation.
What changed on January 1, 2026
California's 2025 Electrical Code, which is Title 24 Part 3 and is based on the 2023 National Electrical Code, took effect on January 1, 2026. Which edition governs a given project is set by the date the permit application was filed, so work designed in one cycle and permitted in the next can land under rules the drawings were not prepared against.
Two changes matter for arc flash marking.
The threshold for the data-bearing label dropped from 1200 A to 1000 A. Equipment sitting in that band was outside the requirement and is now inside it for new and altered work.
The rule expanded from service equipment to service and feeder-supplied equipment. This is the larger change of the two and the one that gets missed, because it reaches distribution equipment downstream of the service that was previously outside the requirement entirely.
Both changes are six months old at the time of writing. Neither converts an existing untouched installation into a violation. Both apply to what you build or alter from here.
Which equipment this touches
There are two different markings and they get conflated constantly. One is a warning, which tells a qualified person that a hazard exists. The other carries values specific to your system, and it is the expensive one because it cannot be produced without analysis.
| Equipment | Marking rule | What that means |
|---|---|---|
| Apartments, condominiums, and houses | Outside the marking rule | The requirement is written for occupancies other than dwelling units. House and common area equipment in a multifamily building is not a dwelling unit, so it can still be in scope. |
| Switchboards, switchgear, enclosed panelboards, control panels, meter socket enclosures, motor control centers | General warning marking applies | Where the equipment is in a non-dwelling occupancy and is likely to be examined, adjusted, serviced, or maintained while energized. This is a warning, not a data label. |
| Service equipment rated 1000 A or more | Data-bearing label applies | The permanent label carrying real values. This is the one that requires a study behind it rather than a sticker. |
| Feeder-supplied equipment rated 1000 A or more | Now in scope | Added by the code edition that took effect in January 2026. Previously the data-label rule reached service equipment only. |
| A 200 A or 400 A panel serving a retail or office suite | Below the data-label threshold | Nowhere near 1000 A. The general warning marking can still apply to qualifying equipment, and the Cal/OSHA duty is separate from both. |
| Equipment you have not touched since it was installed | Governed by the code in force when it went in | A new code edition does not reach backwards into an existing installation. What does reach it is the employer duty, which is not an installation question at all. |
Worth saying plainly, because a lot of writing on this subject implies otherwise: most small commercial tenants are nowhere near 1000 A. If your suite is served by a 200 A or 400 A panel, the data-label requirement is not your problem and no amount of reading about incident energy analysis will make it your problem. Knowing which side of that line you sit on is most of the value of asking the question at all.
The label is the last step
You cannot buy compliance from a label printer
A data-bearing label carries things like the nominal system voltage, the fault current available at that specific equipment, how quickly the protective device ahead of it clears, and the date it was applied. In the fuller version used by maintenance programs, it carries the arc flash boundary and the incident energy or the protection required.
None of those values can be read off the equipment or looked up in a table. They are calculated from your particular distribution: what the utility can deliver, what your transformers and conductors do to it, and how your protective devices are set. That analysis is the actual deliverable. The label is just where the answer gets printed.
This is why the cost surprises people. They believe they are buying labels and they are buying the engineering that makes the labels true. It is also why the worst outcome here is not a missing label but a confident one carrying copied or invented numbers, because the next person to open that equipment will believe it.
Labels also go stale, which owners rarely plan for. The data behind them is reviewed at intervals not exceeding five years under the recognized standard, and that is a ceiling rather than the only trigger. A service upgrade, a new transformer, revised breaker settings, or a significant change in load can alter the calculated result for everything downstream. The labels do not know that happened. Somebody has to.
A building you did not just build
This is where most readers actually are, so it is worth being direct rather than hedging into a sales pitch.
Your existing switchboard was not rendered non-compliant on January 1. The installation code applied when it was installed and it does not follow the equipment forward through later editions. If nothing has been altered, the marking requirement is not the thing to worry about.
Three things do reach an existing building, and they are worth separating.
The employer duty, which never stopped. If people work on or near that equipment, somebody is required to have assessed the hazard and protected them. That obligation does not care how old the gear is.
Any alteration you make. The moment the equipment is worked on, current code comes with the work. This is the most common way older buildings encounter the requirement, and it belongs in the budget for the project rather than arriving as a surprise during inspection.
What contractors will and will not do. A crew that cannot establish the incident energy at a piece of equipment has to either assume the worst case or de-energize. Both cost you something, in schedule or in downtime. This is the practical consequence owners feel long before anyone from an agency turns up, and it is covered in more detail in our guide on staying open during an electrical upgrade.
So the exposure is not uniform. A small suite with a 200 A service and nobody ever opening anything energized is a genuinely different situation from a 2000 A switchboard in a building with staff who service it. Treating those two as the same question is how owners end up buying the wrong thing.
Most of what you will read is the wrong code
This one is worth a section of its own, because it wastes a lot of people's time and it is invisible unless you already know.
The 2026 National Electrical Code exists and is being written about heavily. It changes the arc flash marking rules again, including the amperage threshold. If you search this topic, a good deal of what comes back is describing those changes.
California has not adopted it. The state runs a three-year adoption cycle and is currently on the 2025 California Electrical Code, based on the 2023 National Electrical Code, effective since January 1, 2026. The next edition is expected to take effect on January 1, 2029. California will not be operating under the 2026 national code until then.
So an article explaining that the threshold has been removed entirely is not wrong, it is just describing a rulebook that does not govern your building yet. Anything you read on this subject is worth checking against which code edition your jurisdiction is actually enforcing, and in California right now that answer is the same everywhere.
What to do, in order
Five steps, and the first two cost nothing but attention. Most owners who feel stuck on this are stuck because they skipped straight to asking for a price on a study they may not need.
Write down what you actually have, from the nameplates
Ratings decide everything downstream, and recalled ratings are wrong surprisingly often. What matters is the equipment rating in amperes, whether it is service or feeder-supplied, and the occupancy it sits in. Twenty minutes with the actual nameplates settles most of this question before anyone spends money.
Separate the two questions before asking anyone for a price
What does the code require for work you are planning, and what does Cal/OSHA require for people already working in the building? They have different answers and different urgency. Asking them as one question is how owners end up buying either far more or far less than their situation calls for.
Establish available fault current first
Almost everything on a data-bearing label descends from the fault current available at the equipment. Part of that number comes from the utility and part from your own distribution, so it is a request that takes some lead time. Starting here keeps the rest of the work from stalling later.
Decide which label your situation actually calls for
The code-minimum data label and the fuller incident energy label are different deliverables at different costs. The first satisfies the marking requirement. The second is what a real maintenance program runs on, because it tells a worker the boundary and the protection needed rather than leaving them to derive it.
Put a review date on it the day it goes up
The data behind these labels gets reviewed at intervals not exceeding five years, and any change to the distribution that affects the result resets that clock sooner. Record it wherever you track the building compliance dates you already watch, because a stale label is worse than an absent one: people trust it.
Not sure which of your equipment is actually in scope?
Our team can walk the building, record what the nameplates actually say rather than what the drawings claim, tell you plainly what the current code requires for the work you are planning and what falls outside it, and coordinate the engineering study where one is genuinely needed. Commercial and multifamily work across every city in Santa Clara County.
Common questions
Do we need arc flash labels on an existing building we have not renovated?
The installation code does not reach backwards, so a switchboard installed decades ago was not made non-compliant by a code edition that took effect this year. That is the honest answer to the question as usually asked. It is also not the whole picture, because the marking rule is only one of the two obligations in play. Cal/OSHA requires employers to assess the workplace for people exposed to electric arc hazards and to protect them, and that duty is continuous rather than tied to an install date. So an untouched building can be entirely correct on the first question and still have something to address on the second.
What is the difference between an arc flash label and an arc flash study?
The study is the work and the label is the output. A label carries values such as the nominal system voltage, the fault current available at that equipment, how quickly the protective device clears, and the date it was applied, or in the fuller version the arc flash boundary and the incident energy. None of those are readable off the equipment. They are calculated from your specific distribution, so a label is meaningful only to the extent there is analysis behind it. This is why the pricing surprises people: they think they are buying labels and they are actually buying the engineering that makes the labels true.
Our equipment is under 1000 amps. Does that mean we are finished?
For the data-bearing label requirement, most likely yes, and a great many commercial tenants are comfortably under that threshold. A typical retail or office suite panel is not close to it. Two things still apply. The general arc flash warning marking is not tied to that amperage and can apply to qualifying equipment in a non-dwelling occupancy that is likely to be worked on while energized. And the Cal/OSHA duty toward anyone working on your equipment does not have an amperage threshold at all. Smaller equipment usually means a much smaller obligation, not an absent one.
How often do arc flash labels need to be updated?
The recognized standard has the data supporting the label reviewed for accuracy at intervals not exceeding five years, with the review documented. The interval is the outside limit rather than the only trigger. Any change to the electrical distribution that could affect the calculated result should prompt an update, and those changes are more common than owners expect: a service upgrade, a transformer swap, revised protective device settings, or significant added load can all change the numbers on equipment downstream. A label that no longer reflects the system is a genuine hazard, because the person reading it will believe it.
Who is responsible for arc flash labeling, the landlord or the tenant?
It splits along the same boundary as most other electrical questions in a commercial lease, and the same trap applies: the physical boundary and the financial one are set by different things. Service equipment and main distribution are usually base building and usually the landlord. Equipment inside the premises usually follows the tenant. Where it gets genuinely contested is when an alteration inside the premises triggers work on base building equipment, which is decided by the lease rather than by anything electrical. Our guide on who pays for electrical upgrades covers that boundary in detail. The Cal/OSHA duty is separate again and follows the employer of the people exposed, which may be neither party to the lease.
Can we just buy the labels and put them on ourselves?
You can buy a generic warning label, and putting one on equipment that should carry a warning is better than bare metal. What you cannot do that way is produce a compliant data-bearing label, because the numbers on it are specific to your system and have to be calculated. Nor does a purchased sticker discharge the assessment duty, which is about knowing the hazard and protecting people rather than about the presence of adhesive. The failure mode we would ask you to avoid is the confident label with invented or copied values on it, which is worse than nothing at all.
Does NFPA 70E apply in California?
Not directly, and the distinction is worth holding onto. NFPA 70E is a consensus standard rather than California law in its own right. What has force here is Cal/OSHA, which requires employers to assess the workplace for people exposed to electric arc hazards and to provide appropriate protection. NFPA 70E is the recognized method for doing that assessment and is what a contractor, an insurer, or an inspector will expect to see followed. So the practical answer for a building owner is that you follow it, but the obligation you are satisfying comes from Cal/OSHA rather than from the standard itself.
Keep reading
Can you stay open during an electrical upgrade?
Why crews de-energize rather than work live, and how the one window where power must be off gets kept short.
Who pays for electrical upgrades, landlord or tenant?
The boundary that decides who carries this and the rest of the base building electrical questions.
Commercial service and panel upgrades
The work that most often changes the numbers behind your labels and triggers current code on the equipment.