Arc Flash Studies for Commercial and Industrial Facilities
By Matt Lohens, P.E., MHL Consulting PLLC. Last reviewed: October 2026
Short answer: An arc flash study (also called an incident energy analysis) calculates how much thermal energy a worker could be exposed to at each piece of electrical equipment during a fault. The results drive equipment labels and PPE choices. NFPA 70E requires the study to be reviewed at least every 5 years and updated whenever the electrical system changes. MHL Consulting performs and stamps these studies as a licensed Professional Engineer in AZ, CA, HI, IL, NV, OR, PA, TX, UT and VA.
Do I need an arc flash study?
You probably do if employees work on or near energized equipment such as switchgear, panelboards, motor control centers or disconnects. NFPA 70E requires employers to complete an arc flash risk assessment, and for most facilities an incident energy analysis is how that is done. OSHA does not enforce NFPA 70E by name, but it treats the standard as the consensus reference for workplace electrical safety, and insurers and owners commonly ask for the study.
Separate from 70E, recent editions of the NEC require field-applied warning labels on equipment likely to be worked on while energized (110.16). For service equipment and feeder-supplied equipment rated 1,000 amps or more, the label must show the nominal voltage, available fault current, clearing time of the service overcurrent device and the date the label was applied. Check which NEC edition your jurisdiction has adopted.
What does an arc flash study include?
Data collection: one-line diagram, equipment nameplates, breaker and fuse types and settings, cable sizes and lengths, transformer and generator data.
Short-circuit study: the available fault current at every bus, starting from the utility's value.
Protective device review: the clearing time of each upstream device, since clearing time has a large effect on incident energy.
Incident energy calculation: we run the calculation in SKM PowerTools using the IEEE 1584-2018 method, which accounts for electrode configuration, enclosure size, working distance and system voltage.
Labels and report: equipment labels with the information NFPA 70E 130.5(H) requires, plus a written report with the results.
Mitigation options: where incident energy is high, recommendations such as adjusting trip settings, adding a maintenance mode switch, or zone-selective interlocking.
How often does it need to be updated?
NFPA 70E 130.5(G) says the incident energy analysis must be reviewed for accuracy at intervals not to exceed 5 years, and updated when changes occur to the distribution system. Typical triggers are a new transformer, a utility service change, added or replaced breakers, new generators, or changed protective device settings.
What do I need to send to start?
Existing one-line diagram, or permission for a site walk to build one
The utility's available fault current letter or study, if you have it
Photos of equipment nameplates and breaker or fuse labels
Any prior short-circuit, coordination or arc flash reports
Generator, UPS and large motor information
If you do not have a one-line, we can build one from photos and field notes.
Why use a licensed PE for the study?
Not every jurisdiction requires a stamped arc flash report. Many owners, utilities, insurers and AHJs still ask for one, and a PE's signature means a licensed engineer has reviewed the assumptions and the results. MHL's studies are reviewed and sealed by the same engineer who runs the numbers, so you talk directly to the person responsible for them. We take on facilities of any size and voltage class, from small commercial buildings to medium-voltage industrial plants.
FAQ
Is an arc flash study the same as a short-circuit study? No. The short-circuit study is one input. The arc flash study then uses fault current and protective device clearing time to calculate incident energy.
Can the study reduce my PPE requirements? Sometimes. If the study finds a long clearing time is driving high incident energy, adjusting settings or adding mitigation can lower the PPE category at that equipment.
Do I need a new study after replacing one breaker? Replacing a protective device can change clearing time and fault current, so the study should be reviewed at minimum.
What states do you cover? We are licensed in AZ, CA, HI, IL, NV, OR, PA, TX, UT and VA.
Next step
Send us your one-line diagram and a short description of the facility, or book a 15-minute call. We will tell you what data is needed and what the study will cover.
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