Electrical Code by 50 States (and Why Your Local Inspector Still Has the Final Say)
People search “what NEC does my state use?” because they’re trying to do the right thing — especially for generator inlets, interlocks, transfer switches, and panel work. Here’s the practical truth: your state may adopt a code baseline, but your local AHJ (building department / electrical inspector) is the final authority for permits and inspections.
Why “Electrical Code by State” is never one simple chart
You’ll see charts online claiming “State X uses NEC 2020” and “State Y uses NEC 2017.” The problem: states update, counties amend, and cities can layer rules on top. Even when the NEC baseline is clear, inspections and permits can differ.
A state may adopt an NEC edition or incorporate it into a broader building code.
Cities/counties can add requirements (labeling, permits, equipment listing, inspections).
The inspector decides what passes for your specific job and installation method.
Panel labels + manufacturer instructions matter, especially for breakers/interlocks.
The 5-minute method: verify your state + local rules
Use this approach and you’ll be more informed than 95% of people Googling code charts. Your goal is to capture three things: (1) baseline code, (2) local amendments, and (3) permit/inspection process.
Step 1 — Find your state “official source”
- Your state’s building code council / department of safety / labor & industry (names vary).
- Your state legislature / administrative code site (often the most “official” legal language).
- State electrical licensing board resources (often explains what’s enforced in practice).
Step 2 — Find your local AHJ page
- Search: “[your city/county] electrical permit generator inlet interlock transfer switch”
- Look for permit forms, inspection checklists, and “approved equipment” notes.
- Find the phone/email for the electrical inspector or permit office.
Step 3 — Save proof
- Screenshot the page that states the current rule baseline (or print-to-PDF).
- Save the permit checklist and inspection notes.
- Keep the panel label + interlock instructions with your permit packet.
What actually varies (the stuff that affects homeowners)
The NEC is a national model code, but real life differs by state/local adoption and enforcement. These are the items that most commonly surprise homeowners — especially for backup power work:
- Permit & inspection rules (required vs optional; homeowner permits vs licensed-only).
- Equipment listing requirements (UL/ETL listing, “panel-matched” interlocks, labeling).
- Generator inlet location rules (weatherproofing, working clearance, bonding/neutral handling).
- GFCI/AFCI enforcement details (new circuits vs existing; unfinished spaces; receptacle rules).
- Service disconnect and panel upgrades (when required, how evaluated).
State notes tool (use this while you research)
As you verify your rules, capture the essentials here. This tool stores notes in your browser (not on our server). You can copy/paste into your project notes.
What to ask your AHJ (copy/paste script)
If you’re planning a generator inlet + interlock or a manual transfer switch, this short message saves time and prevents “redo” work.
“Hi — I’m a homeowner at [address/area]. I’m planning a [generator inlet + interlock / manual transfer switch].
1) Do you require a permit and inspection for this work?
2) Are homeowners allowed to pull the permit, or must a licensed electrician do it?
3) Do you require listed/panel-matched interlock kits and specific labeling?
4) Is there a checklist or preferred method you want followed?
Thanks — I want to make sure this is code-compliant and safe.”
Before you connect a generator: quick safety gate
If you can’t honestly check these boxes, your safest move is to pause and get help from your AHJ or a licensed electrician.