When standard solar designs meet local code reality

Every solar installation in the United States is designed to the National Electrical Code (NEC). What varies is which edition applies and how it has been modified locally. Many states adopt the NEC with local amendments that change or delete specific provisions, and a handful, including Illinois, leave adoption to individual jurisdictions rather than setting it statewide. Major cities such as Chicago run their own electrical codes outright. The binding requirement on a given project, in other words, is often not the model code an engineer knows but the local amendment layered on top of it.

This is not limited to the electrical code. The International Building Code (IBC) and International Fire Code (IFC) are adopted and amended the same way, so requirements for equipment placement, fencing, and access shift from one jurisdiction to the next. An engineer can know the NEC thoroughly and still be caught, because the governing rule lives in a local amendment. When that amendment is not identified during early design, it surfaces later, at the permit counter or during construction, where a change made to achieve compliance is far more expensive than the same decision made on paper.

The response is due diligence at the preliminary design stage: confirming the governing code editions and local amendments before the design commits, and incorporating the requirements of the other stakeholders who constrain the design, civil and utility among them, at the same early point. This is the methodology I developed while leading the engineering on a multi-site portfolio of Illinois community-solar projects that entered design in 2024, and it is the subject of this article: not what the array should look like, but what a team should establish before the first line is drawn, so that local requirements shape the design rather than interrupt it.

Why a standard design does not travel

The consequence for engineering is that a portfolio-standard electrical approach does not survive contact with individual authorities having jurisdiction (AHJs). The Chicago Electrical Code is a useful illustration. It limits cable tray to conductors of 50 volts or less. Rooftop PV circuits run well above that, so a cable-tray routing strategy that is compliant in a neighboring jurisdiction has to become conduit. Discovered during design, that is a routing decision. Discovered after the permit set is issued, it is a redesign that propagates through conduit schedules, attachments, and load calculations.

Utility interconnection behaves the same way. Distributed energy resources interconnect under IEEE 1547, the national standard, but the specific requirements, protection settings, and equipment footprint differ by service territory and are often not final until the utility has reviewed customer design documents. Civil and site conditions add a third layer, determining where ground-level equipment can physically sit, which rarely matches what the electrical concept assumed.

What to establish before preliminary design

The methodology begins by establishing three categories of requirement before preliminary design is fixed, rather than discovering them after the permit package is in review. Most teams eventually gather all of it; the difference between a smooth project and a redesign is when.

Code and local requirements. Verify the local code amendments that apply to the jurisdiction, not the state default or the edition used on a project a few miles away. Confirm the local treatment of ground-level equipment as well: permitted locations, front-yard restrictions, setbacks, screening and fencing obligations, and whether a variance is realistically available. Together these determine routing method, equipment siting, and screening scope.

Utility. Establish interconnection viability from the feasibility study, then obtain the utility’s demarcation drawings to confirm the point of interconnection, metering arrangement, and the equipment footprint the utility will require. Check the demarcation drawings against the local amendments for conflicts, and resolve them before the design commits rather than after, since the two are issued by different authorities and are not reconciled for you.

Civil and site. Pull the survey, recorded easements, and utility locates before layout, and identify stormwater, setback, and fire-access constraints early. This determines the ground area actually available for equipment and the trench routes that connect it, which is frequently the binding constraint on an otherwise workable electrical concept.

Design around the constraints, then review in parallel

With those inputs in hand, the preliminary design can be built around real conditions rather than an idealized concept that later has to be unwound. In practice this means reviewing site layouts, equipment placement, and single-line diagrams jointly with electrical, civil, and permitting stakeholders before the issue-for-permit package is finalized, rather than routing the drawings to each discipline in turn.

The second change I made is procedural. Utility review, AHJ review, and civil refinement are commonly treated as serial gates, each beginning when the last one ends. Run them concurrently instead, and resolve the comments together. The failure this avoids is a familiar one: a revision made to satisfy the AHJ creates a conflict with the utility’s requirements, which is then discovered on the next pass. When AHJ-driven equipment relocations are reflected in the utility and civil documents in the same cycle, and utility-driven changes are carried directly into the permit drawings, the approval pathways stop working against each other.

Early and proactive engagement with the AHJ belongs in the same category. A short conversation confirming the governing code edition and any local amendments, before permit review begins, costs far less than discovering the answer through a correction notice.

A method that travels

The methodology is not specific to Illinois. Wherever code authority sits with local jurisdictions, or a statewide code is subject to local amendment, the same approach transfers: treat the jurisdiction as a design input, gather it early, and review the approval pathways together rather than in sequence. Early, coordinated interconnection planning is consistent with the direction of the U.S. Department of Energy’s distributed energy resource interconnection roadmap.

It does not eliminate revisions. Layouts change as module availability and market conditions shift. Review queues and staffing at the permitting office are outside any engineer’s control, and no amount of preparation shortens them. What front-loaded coordination addresses is the narrower and more avoidable category: the redesign that happens because a knowable jurisdictional requirement was not established before the design committed. That is the rework worth engineering out.

For a market now scaling solar across many jurisdictions at once, resolving requirements up front is less a matter of process preference than of design discipline.

Archit Patnaik, PE, PMP, is a senior project manager at Pure Power Engineering specializing in solar PV and battery energy-storage systems. He leads electrical engineering for solar and storage projects serving developers, EPCs, and asset owners, including a multi-site Illinois community-solar portfolio, and is a NABCEP-certified PV Installation Professional.