O'Fallon, MO Solar Energy: Panel Permits (2026)
Key Facts
- Residential permit fee
- $50
- Commercial/industrial permit fee
- $100
- Ground-mount height cap (residential)
- 15 feet
- Ground-mount location
- Rear yard only
- Over 1 acre of panels
- Requires conditional use permit
- Parallel roof mounting max rise
- 8 inches above roof surface
Summary
O'Fallon requires a building permit before any solar energy system is installed, with a $50 fee for residential jobs and $100 for commercial or industrial ones. Ground-mounted arrays go in the rear yard only and are capped at 15 feet in residential zones.
Building Permit. It shall be unlawful for any renewable energy system to be constructed, erected, and/or installed without a building permit. Renewable energy systems shall comply with all applicable Building, Mechanical, Plumbing, and Electrical Codes adopted by or applicable to the City of O'Fallon. A building permit fee shall be fifty dollars ($50.00) for systems installed on residential property and one hundred dollars ($100.00) for commercial or industrial properties.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4860992; v58 updated 2026-05-14; through 05-14-2026).
Full Breakdown
Under O'Fallon Code § 400-920, it is unlawful to construct, erect, or install any renewable energy system, including a solar array, without a building permit, and the system must comply with the City's Building, Mechanical, Plumbing, and Electrical Codes. The permit fee is $50 for residential property and $100 for commercial or industrial property. Roof-mounted and small ground-mounted systems serving a single-family home, mobile home, or a building of four units or fewer can be approved administratively by the Planning and Development Department; larger systems need site plan approval, and any ground-mounted array over one acre (counting panels, spacing, and access drives) needs a conditional use permit under Article VII of Chapter 400.
Section 400-930 sets the design rules. Ground-mounted systems are allowed only in the rear yard, cannot exceed the height of the principal structure, and are capped at 15 feet in any residential zoning district; exterior electrical and plumbing lines must be buried, and the ground beneath the array must be kept clear with mulch, chat, or rock rather than weeds. Roof-mounted arrays on pitched roofs must be mounted flush or parallel, with parallel mounting no more than 8 inches above the roof surface; a different pitch than the roof itself triggers a conditional use permit, and no roof-mounted array may exceed the roofline. Flat-roof arrays must be screened per § 400-278. An applicant must submit a written structural certification from a Missouri-licensed structural engineer covering panel weight per square foot and wind loads.
Section 400-940 lists the application package: the building permit with electrical, plumbing, and structural drawings, the engineer's seal, a plot plan showing north arrow, roof or lot dimensions, ridge lines or setbacks, nearby vents or trees, panel array size and layout, support structure or footing details, sample photos of panel and roof colors, and, for grid-tied systems, a copy of the utility company's design approval letter.
Violations & Fines
Solar work done without the required building permit falls under the City's general penalty provision, O'Fallon Code § 100-010: a fine of up to $500 and/or up to three months' imprisonment where no more specific penalty applies. Because solar installations are also zoning matters, an unpermitted or non-compliant array can instead be charged under the tiered municipal-ordinance schedule tied to RSMo §§ 89.120 and 89.490 (zoning violations), which runs from a $200 maximum for a first violation in twelve months up to $450 for a fourth or later violation in that period, plus court costs unless the defendant is found indigent.
Frequently Asked Questions
Do I need a permit to put solar panels on my O'Fallon roof?
Can I put ground-mounted solar panels in my front yard?
What if my roof-mounted panels won't sit flush with the roof?
Does a large ground-mounted solar array need extra approval?
Sources & Official References
Other rules in O'Fallon
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