Ask what electrical code applies to your house and you'll get a surprisingly slippery answer. The National Electrical Code updates every three years — but Missouri has no statewide electrical code, so what's actually enforced depends on your county or city. This is how it actually works around here, and what the recent code changes mean for your house.
The local reality (this is the part most articles get wrong)
Missouri adopts electrical codes locally, not statewide. Each county and municipality picks its own edition, on its own schedule.
St. Charles County enforces the 2020 NEC — adopted by county ordinance in November 2023. Not the newest edition (the 2023 exists, and the 2026 cycle is rolling out nationally), but the 2020 book is what the county's inspectors hold your project to.
Cities inside the county can differ. The City of St. Charles maintains its own electrical code article, and other municipalities set their own adoptions and amendments. Two houses a mile apart can genuinely be inspected against different editions.
What this means for you: when you read a national article about "new code requirements," it may describe an edition your jurisdiction hasn't adopted yet. Before any project, the right question isn't "what does the NEC say?" — it's "what does my jurisdiction enforce?" (When we pull your permit, answering that is our job, not yours.)
The changes that matter, whichever edition you're under
The last few code cycles have pushed hard in one direction: more protection against shock and fire. These are the ones homeowners actually feel.
GFCI protection keeps expanding
Ground-fault protection — the outlets with TEST/RESET buttons — has expanded steadily: bathrooms, kitchens, garages, outdoors, basements, laundry areas, and (in recent editions) more appliance circuits like dishwashers. GFCIs prevent electrocution, and retrofitting them is one of the cheapest meaningful safety upgrades a house can get, grandfathered or not.
AFCI protection covers most living areas
Arc-fault breakers detect the sparking of damaged wires and loose connections — the stuff that starts fires inside walls. Bedrooms have required them for over two decades, and coverage has grown to most living areas. Standard breakers cannot do this job.
Whole-home surge protection (2020 edition — the one our county enforces)
The 2020 NEC requires a surge protective device at the service for new and replaced panels. If we upgrade your panel in St. Charles County, it gets surge protection — not as an upsell, as code. Given what's plugged into a modern house, it's one of the code's better recent calls.
Tamper-resistant receptacles
New and replacement outlets in homes must be tamper-resistant — built-in shutters that stop a child from pushing something into one slot. Most outlets sold today are TR by default; check for the "TR" stamp.
EV charging provisions
Newer editions add rules for EV charger circuits, load calculations, and load-management systems. Even where the newest edition isn't adopted, we install chargers to current best practice — the physics of a 40-amp continuous load doesn't care which book is on the inspector's desk.
Grandfathering: what existing homes must (and needn't) do
The general rule: an installation that met code when it was built doesn't have to be updated every time the code changes. Your 1995 wiring isn't "illegal" because editions have advanced.
Where current code kicks in: - New work — additions, new circuits, panel upgrades must meet the currently enforced edition - Renovations — the new portion meets current code; scope determines how far that reaches - Hazards — genuinely dangerous conditions need fixing regardless of vintage - Insurance — insurers set their own requirements and sometimes demand updates code doesn't
Worth doing even when grandfathered: GFCI in wet areas, working smoke/CO detectors, and surge protection. Code sets the floor for new work; it says nothing about what's wise in an older home.
What actually gets flagged around here
From inspections and home sales in our area, the recurring list:
- Missing GFCI protection in bathrooms, kitchens, garages
- Ungrounded three-prong outlets (tester shows "open ground")
- Double-tapped breakers — two wires under one screw
- Federal Pacific and Zinsco panels — documented failure-to-trip histories
- Aluminum branch wiring (mid-'60s to early-'70s homes)
- Unpermitted work — usually obvious, always a problem at sale time
None of these are exotic. Most have straightforward fixes, and knocking them out before listing a house is far cheaper than negotiating them under contract.
Permits: the boring superpower
When one's required (typical local practice): new circuits, panel changes, service upgrades, and most work beyond like-for-like replacement.
Why we're sticklers about it: an inspected job is a documented job. That documentation is what protects you at sale time, in an insurance claim, and with the next contractor who opens the panel. We handle the permit and meet the inspector — it's built into how we quote.
Planning work and not sure what applies? That's a normal question, not a dumb one. The adoption map really is confusing. Schedule a consultation and we'll tell you exactly what your jurisdiction requires for your project, then handle the permit ourselves.