⚡ Sub-Panel Quick Facts
Permit required? Yes — virtually all U.S. jurisdictions.
Owner-builder allowed? Same rules as main panel — depends on your state and city.
Critical code point: In detached structures, the neutral and ground MUST be separated at the sub-panel (not bonded together as they are at the main panel).
Feeder wire permit: The circuit feeding the sub-panel also requires a permit separately or as part of the same application.

What Does a Sub-Panel Permit Cover?

A sub-panel permit covers the installation of a secondary distribution panel that receives power from the main panel via a feeder circuit. The permit typically covers: the sub-panel enclosure and breakers, the feeder conductors (the wires from main to sub), the grounding electrode system at the sub-panel location, and the circuits fed from the sub-panel.

In detached structures (garage, workshop, barn), the permit almost always includes the feeder run — whether it's run overhead or underground — as well as the sub-panel itself.

The Most Critical Sub-Panel Code Requirement: Neutral-Ground Separation

This is the most commonly failed inspection point for sub-panel work, and it trips up even experienced DIYers. At the main service panel, the neutral bar and ground bar are bonded together (connected). This is correct and required at the main panel only.

At a sub-panel, the neutral bar and ground bar must be separated — they must be on separate bars with no bonding jumper between them. If they are bonded at the sub-panel, current will flow on the grounding conductors, creating a safety hazard and a code violation. Inspectors check for this specifically on every sub-panel inspection.

Underground vs. Overhead Feeder to Detached Structure

For detached structures, the feeder from the main panel can run overhead (on a weatherhead system) or underground (in conduit). Underground is more common in new installations and is cleaner aesthetically. Key requirements:

  • Underground: Minimum burial depth is 24 inches for circuits in conduit, 6 inches for low-voltage, and varies for direct-burial cable (typically 24 inches for 120/240V). Always use conduit for any run under a driveway or paved surface regardless of amperage.
  • Overhead: Service entrance cable must clear the ground by at least 10 feet in pedestrian areas, 12 feet for driveways, and 18 feet over public roads. Must have a proper weatherhead and drip loop.
  • Both methods require a permit for the feeder run itself.

How Much Does a Sub-Panel Permit Cost?

Sub-panel permit fees are generally in the same range as main panel permits — $50–$200 in most jurisdictions. Some jurisdictions add a separate fee for the feeder circuit. Use our permit cost guide for regional ranges.

Sub-Panel Permit FAQ

In most jurisdictions, a single permit covers both the feeder circuit and the sub-panel installation — you describe both on the same application. Some jurisdictions may require two separate permits (one for the panel work, one for the circuit/wiring). Ask your building department when you apply: "Does a sub-panel permit cover the feeder circuit from the main panel, or do I need a separate permit for the feeder?"
Yes. NEC 250.32 requires a grounding electrode system at any building or structure supplied by a feeder or branch circuit — which means your detached garage or workshop needs its own ground rod (or other grounding electrode), connected to the sub-panel's ground bar. This is in addition to the grounding conductors in the feeder. A single 8-foot ground rod driven at the structure is the most common solution. Inspectors check for this specifically.
Only for existing installations that were done before the 2008 NEC update. The current NEC (2008 and all later editions) requires a 4-wire feeder (two hots, a neutral, and a separate ground conductor) for any new or modified feeder to a separate structure. If you're installing a new sub-panel or modifying an existing feeder, you must use 4 wires. A 3-wire feeder to a detached structure will fail inspection under current code.
Disclaimer: Sub-panel permit requirements vary by jurisdiction and code edition. Always verify with your local building department before starting work.

Related Pages

Owner-Builder by State 📋 Inspection Checklist ⚡ Permit Wizard