Running power to a detached structure—a garage, workshop, storage building, or guest house—almost always requires an electrical permit. The scope varies widely: a simple 20-amp circuit in a single-car garage is different from a 200-amp subpanel feeding a full workshop or ADU. The permit requirement hinges on three things: whether you're running the line overhead or underground, the distance from your main panel, the amperage load, and local amendments to the National Electrical Code.
The National Electrical Code (NEC Article 225) governs all outside branch circuits and feeders. Most jurisdictions adopt the NEC wholesale, though some states (Florida, California, New York) add climate-specific amendments. The IRC R105 requires permits for any electrical installation that materially changes the use or load of the building system—which running power to a new detached structure always does.
The key decision: is this a branch circuit (a single outlet or light circuit at 15–20 amps) or a feeder (a larger feed serving multiple circuits or a subpanel)? Branch circuits under certain distances may qualify for expedited or over-the-counter permit review in some jurisdictions. Feeders—especially those over 100 feet—almost always require plan review, trench inspection (if underground), and post-installation inspection.
Before you dig or run conduit, call your local building department. A 10-minute conversation will clarify whether you need a full electrical permit, a simplified permit, or whether the work falls into a narrow exemption category. Most jurisdictions process electrical permits within 1–4 weeks; some allow over-the-counter approval for straightforward branch circuits.
When running power to a detached structure requires a permit
The NEC and nearly all adopted building codes require a permit for any electrical work that adds a new circuit or feeder to a structure not previously wired. This includes running power from your main panel to a detached garage, shed, workshop, or ADU. There is no blanket exemption for 'small' jobs. The threshold is functional, not size-based: if you're installing outlets, lights, or a subpanel in a detached building, you need an electrical permit.
The scope of work determines permit complexity. A single 120-volt, 15-amp branch circuit to a detached garage—just one or two outlets and maybe a light—may qualify for an expedited or over-the-counter permit in some jurisdictions. These typically file and get approval the same day or within 1–2 business days. A full feeder running 100+ feet from the main house panel to a detached structure with a subpanel, multiple circuits, or a 240-volt appliance requires full plan review, typically 2–4 weeks, plus multiple inspections.
Underground vs. overhead changes both code requirements and permit scope. Underground runs must comply with NEC Article 300 (wiring methods) and local frost-depth requirements. A Wisconsin detached garage 48 inches below grade; a Florida detached workshop may only need 18 inches. Overhead runs must clear roofs, decks, and walkways per NEC Article 225.18 (height clearances). Underground permits usually require a trench inspection before backfill; overhead permits inspect the final installation. Underground runs typically take 1–2 weeks longer because inspectors must schedule a trench walk.
Distance from the main panel affects whether you need a subpanel. If the detached structure is within about 50–75 feet and the circuit load is modest (a single 20-amp circuit for a few outlets), you might run a branch circuit directly from the main panel or a subpanel in the main house. Beyond 75 feet, voltage drop becomes a concern; NEC Article 210.19(A) limits voltage drop to 3% on branch circuits and 5% for branch circuit plus feeder. Most electricians install a subpanel in the detached structure itself when the distance exceeds 100 feet or the load exceeds 60 amps. This requires a separate subpanel permit and, in most jurisdictions, a licensed electrician.
Amperage and feeder size determine permit fee and inspection rigor. A 20–30 amp circuit for a garage might cost $75–$150 and require two inspections (underground/conduit roughin, final). A 100–200 amp subpanel can cost $200–$500 and require three inspections (footing/conduit location, underground/roughin, final). Most jurisdictions price electrical permits as a flat fee for branch circuits or as 1–2% of total project valuation for feeders and subpanels. Ask the building department for their fee schedule before you file.
The permit application itself is straightforward but must be complete. You'll submit a one-line diagram showing the main panel, the detached structure, the circuit/feeder size (amps, voltage), the conduit/cable type, the route (overhead or underground with distances), and the load calculation. Incomplete applications get rejected immediately—expect a 3–5 business day turnaround for resubmission. The most common rejection: a site plan or one-line diagram that doesn't clearly show the route, distance, conduit type, and point of connection to the main panel.
How detached-power permits vary by state and region
Most states adopt the NEC as-written, but some add significant amendments. Florida's Building Code requires all outdoor wiring in hurricane zones to use GFCI protection and impact-resistant materials; a Florida detached-structure feeder over 75 feet may trigger additional conduit and protection requirements not needed in Wisconsin or Ohio. California's Title 24 energy code adds mandatory solar-ready equipment for new detached structures above a certain size—this doesn't directly affect the electrical permit process but can add cost and complexity to the design. New York City has adopted the NEC but requires all detached-structure work to be performed by a licensed electrician and inspected by a Department of Buildings inspector, not a private or municipal third-party inspector. Always confirm whether your state has adopted amendments or whether your city/county has supplementary rules.
Frost depth and burial requirements vary dramatically by region. A detached-structure feeder in Minnesota, Wisconsin, or Vermont must be buried below the frost line—typically 48–60 inches. This means running conduit at significant depth, which increases labor costs and permit complexity. A feeder in Georgia or South Carolina might only require 18 inches burial. If your soil is rocky or wet, some jurisdictions allow alternative burial methods (conduit sleeves, concrete encasement). These regional variations don't change the permit requirement, but they do change cost and timeline. Confirm your local frost depth and burial code before planning an underground run.
Permitting speed and inspection availability differ by jurisdiction. Urban areas (Los Angeles Department of Building and Safety, Chicago Department of Buildings, New York City DOB) typically process electrical permits within 2–3 weeks but may have long inspection backlogs. Rural counties may process permits faster (1–2 weeks) but inspectors may only be available on certain days, delaying the job. Some jurisdictions allow homeowners to pull electrical permits themselves; others (Florida, Illinois, New York) require a licensed electrician to file. Check your state's electrical licensing board website or call the local building department to confirm who can file and whether inspections can be scheduled online.
Subpanel requirements vary. Most jurisdictions require a subpanel in the detached structure itself if the distance from the main panel exceeds 100 feet or if the load exceeds 100 amps. A few jurisdictions (notably some Arizona and Nevada jurisdictions with long properties) allow longer branch-circuit runs using larger wire and GFCI protection. This is rare and always requires an engineer-stamped design. If you're running power more than 150 feet, assume you'll need a subpanel and plan accordingly—subpanel permits typically cost $50–$100 more and take an extra week because they require a separate subpanel inspection.
Common scenarios
Single 20-amp circuit, underground, 60 feet from main panel to detached garage
You need an electrical permit. This is a straightforward branch circuit—likely 12 AWG wire in underground conduit running from a 20-amp breaker in the main panel to one or two outlets in the garage. The permit is simple: $75–$150 depending on your jurisdiction. You'll submit a one-line diagram showing the panel, the garage location, the wire size, the conduit type, and the distance. Most jurisdictions approve this over-the-counter or within 1–2 business days. Inspections: the inspector will walk the trench before you backfill (underground roughin), then return for a final after all outlets are wired and tested. Total time from filing to final inspection: 2–3 weeks in most areas. You may be able to pull this permit yourself; call your building department to confirm whether a licensed electrician must file or if homeowners can pull electrical permits in your jurisdiction.
100-amp feeder, underground, 120 feet from main panel to detached workshop with subpanel
You definitely need an electrical permit, and this is more complex. The distance exceeds 100 feet, so you'll need a subpanel in the workshop. The permit will require a site plan showing the main house, the workshop, the distance, and the conduit route (preferably along a driveway or property line to avoid utility conflicts). You'll also need a load calculation showing the subpanel amperage (100 amps, 240 volts). This typically requires a licensed electrician to file—confirm with your local building department or state electrical board. Permit fee: $150–$300. Plan review: 2–3 weeks. Inspections: footing inspection before the conduit is buried (to confirm location and depth per frost-depth code), underground roughin before backfill, subpanel installation roughin, and final. Total timeline: 4–6 weeks. If the trench crosses under a driveway, you may need a separate conduit-crossing detail or engineer approval. Check with the local public works department too, in case there are utility easement or driveway-crossing restrictions.
Overhead line, 15 amps, 40 feet from main panel to detached garage
You need an electrical permit for the overhead run, even though it's short and low-amperage. NEC Article 225 requires permits for all outside feeders and branch circuits serving detached structures, regardless of voltage. The permit is typically expedited: $50–$100, approved over-the-counter or within 1–2 business days. You'll submit a diagram showing the run from the main panel to the garage, the wire size, the clearances (at least 10 feet above grade, 8 feet above a driveway, 12 feet above a roof per NEC 225.18). The inspector will do a final visual to confirm clearances and that the line is properly secured and grounded. One inspection, typically 1–2 weeks after filing. Overhead runs are usually faster than underground because there's no trench inspection.
200-amp service upgrade: main house panel + new 100-amp subpanel in detached ADU, 80 feet away, underground
You need a full electrical permit (plus building permits for the ADU itself). This is a complex project: main service upgrade, feeder to the detached structure, and a new subpanel. The permit requires an engineer-stamped one-line diagram, a detailed site plan showing the underground conduit route, and load calculations for both the main panel and the subpanel. Fee: $300–$500 or more, depending on total project valuation. Plan review: 3–4 weeks (may require third-party review in some jurisdictions). Inspections: service upgrade pre-work (old meter and main breaker inspection before the new service is installed), footing/conduit location before burial, underground roughin, subpanel roughin, final. Total timeline: 6–10 weeks. You'll definitely need a licensed electrician to design and file this. Coordinate with the building department early; some jurisdictions require the ADU building permit to be approved before the electrical permit can issue.
Adding an outlet to an existing detached garage that already has power
You do NOT need an electrical permit if you're adding an outlet to a garage that already has a dedicated circuit. This is a modification to an existing circuit, not a new installation. You can run wire from an existing outlet or junction box to a new outlet location without a permit—as long as you stay within the existing circuit's amp rating (usually 15 or 20 amps). However, the work must meet code: wiring must be in conduit or cable appropriate for the location (NM cable indoors, UF cable buried, THWN in conduit for wet areas), all outlets must be GFCI-protected if outdoors or near water, and the work should be done per NEC standards. If you exceed the circuit's capacity, need a new circuit breaker, or run new wire from the main panel, then you need a permit. When in doubt, call the building department. The distinction between 'adding to an existing circuit' and 'adding a new circuit' is the main gray area—and the 30-second phone call to confirm is worth it.
What to file and who can pull the permit
| Document | What it is | Where to get it |
|---|---|---|
| Electrical Permit Application | One-page form (varies by jurisdiction) asking for property address, owner name, scope of work, and estimated project value. Most jurisdictions have this available online or at the counter. | Your local building department website or in-person at the permit counter. Common names: 'Electrical Permit Application', 'Electrical Work Permit', 'Request for Electrical Permit'. Search your city + 'electrical permit application'. |
| One-Line Diagram | A simple schematic showing the main electrical panel, the detached structure, the feeder or branch circuit, wire size (gauge and type), amperage, voltage, conduit type, and the route (overhead or underground with distance). Can be hand-drawn or computer-generated. Must show point of connection to the main panel and point of termination in the detached structure. | You prepare this. A licensed electrician can provide a detailed version; a homeowner can sketch a basic version for a small branch circuit. Templates are available from many building departments online. |
| Site Plan | An overhead view of your property showing the main house, the detached structure, the proposed conduit/line route, the distance between buildings, and any above-ground or underground obstacles (trees, utilities, driveways). Need not be surveyor-grade; a sketch with measurements is usually acceptable for simple jobs. | You prepare this from a satellite image, property survey, or sketch. Most permit applications only require this for feeders over 75 feet or subpanels. For short branch circuits, the building department may waive it. |
| Load Calculation (for feeders and subpanels) | A calculation showing the demand on the feeder or subpanel, based on connected loads (outlets, lights, appliances). For a simple garage with a few outlets, a rough estimate is fine. For a workshop or ADU, a detailed calculation per NEC Article 220 is required. A licensed electrician typically prepares this. | Your electrician prepares it if you hire one. For DIY small projects, the building department may accept a simple list of anticipated loads. Ask before filing. |
| Proof of Licensed Electrician (in some states) | Copy of the electrician's license and contractor's license (if required by your state). Florida, Illinois, New York, and others require all electrical work to be performed by and filed by a licensed electrician. Some states allow homeowners to file for their own property but still require a licensed electrician to do the work. | Your electrician provides this. Check your state's electrical licensing board website (search '[State] electrical licensing board') to confirm whether homeowners can pull permits or if a licensed electrician must file. |
Who can pull: This varies sharply by state and jurisdiction. In most states (Minnesota, Wisconsin, Colorado, Georgia, etc.), a homeowner can pull an electrical permit for work on their own property and either do the work themselves (if they're competent) or hire a licensed electrician. A few states—notably Florida, Illinois, and New York—require a licensed electrician to file the permit and perform the work, even if the homeowner is the property owner. Some states split the difference: homeowners can pull the permit but must hire a licensed electrician to do the work and sign off. Your state's electrical licensing board website will specify. If unsure, call your local building department and ask: 'Can a homeowner pull an electrical permit for a detached structure, or must a licensed electrician file?' They'll have a clear answer.
Why detached-power permits get rejected (and how to fix them)
- One-line diagram is missing or unclear: doesn't show the wire size, conduit type, distance from main panel, or point of connection to the breaker.
Redraw the one-line diagram to show: main panel → feeder/branch circuit size (e.g., '2 AWG, 100 amps, 240V') → conduit type (PVC, aluminum, rigid) → distance ('120 feet') → detached structure → subpanel or outlet. Label the breaker size in the main panel. This is the #1 rejection reason—get it right and most permits sail through. - Site plan is missing or doesn't show the distance or route from the main panel to the detached structure.
Submit a simple overhead sketch showing the main house, the detached structure, the proposed conduit route (along the driveway, fence, or direct), and the distance in feet. Include any above-ground obstacles (trees, power lines, roof eaves). Even a 30-second hand-drawn sketch satisfies most jurisdictions for distances under 100 feet. - Permit application is filed under the wrong category or is incomplete (missing owner contact info, property address, or scope description).
Confirm the correct permit type with the building department before submitting. Electrical work is often filed under 'Electrical Permit' or 'Subpermit—Electrical'. Make sure every field on the application is filled in: owner name, address, phone, email, and a clear one-sentence scope ('Run 100-amp feeder from main panel to detached garage subpanel, 120 feet underground'). Incomplete applications get kicked back with a 3–5 day turnaround. - No Licensed Electrician signature or contractor information (in states that require it).
Check your state's requirement first. If a licensed electrician is required to file, include a copy of their license and contractor information on the application. If not required, this is a non-issue. Don't assume—call the building department. - Voltage drop or wire sizing is inadequate for the distance and load.
For runs over 75 feet, calculate voltage drop per NEC Article 210.19. If you're running a 20-amp circuit 120 feet, a 12 AWG wire (standard for 20 amps in short runs) will drop too much voltage. You'll need 10 AWG or larger—or a subpanel closer to the load. If you're unsure, ask an electrician or use an online voltage-drop calculator (search 'NEC voltage drop calculator'). The building department may reject the permit if wire sizing is inadequate. - Frost depth or conduit burial depth doesn't meet local code.
Confirm your local frost depth with the building department or the local county soil survey (USDA NRCS). In northern climates (Minnesota, Wisconsin), burial is often 48–60 inches below grade. In southern climates, 18–24 inches. If you can't bury deep enough (bedrock, high water table), propose an alternative like concrete encasement or above-ground conduit. Resubmit with a note explaining the change.
Permit fees, inspection costs, and total project budget
Electrical permit fees are usually flat-fee or based on project valuation. A simple 20-amp branch circuit to a detached garage typically costs $50–$150; a 100-amp feeder with subpanel can run $200–$500. Some jurisdictions charge 1–2% of the total electrical project cost (materials + labor). Ask your building department for their fee schedule before filing—most post it online or will email it on request.
Inspection fees are usually bundled into the permit fee, not charged separately. Expect 1–3 inspections depending on scope: for an underground run, the inspector walks the trench before backfill; for a subpanel, there's a roughin inspection before the panel is energized and a final after all circuits are wired. Each inspection typically takes 15–30 minutes onsite.
Electrician labor costs—not permit costs—will dominate your budget. A simple 60-foot underground branch circuit to a garage typically costs $1,500–$3,000 in labor (trenching, conduit, wire, outlets, testing). A 120-foot feeder with subpanel can run $3,000–$8,000 depending on soil conditions, conduit type, and local labor rates. Always get a bid from a licensed electrician before deciding whether to DIY or hire out. The permit fee itself ($75–$300) is usually a small fraction of total project cost.
| Line item | Amount | Notes |
|---|---|---|
| Simple branch circuit (20–30 amps, under 75 feet) | $50–$150 | Flat fee or based on valuation. Usually approved over-the-counter in 1–2 days. |
| Feeder + subpanel (75–100+ feet, 60+ amps) | $150–$400 | May include plan review. Expect 2–4 weeks. Some jurisdictions charge 1–2% of project valuation instead. |
| Service upgrade + feeder + subpanel (complex job) | $300–$600+ | May require third-party plan review. Factor in engineer-stamped design if required. |
| Reinspection fee (if initial inspection fails) | $25–$75 | Charged if the inspector finds code violations. Rare if the electrician is licensed and careful. |
| Licensed electrician labor (60-foot branch circuit, DIY trenching) | $1,500–$3,000 | Cost varies by region, conduit type, and soil. Underground runs are more expensive than overhead. |
| Licensed electrician labor (120-foot feeder + subpanel) | $3,000–$8,000 | Includes trench, conduit, wire, subpanel, breakers, and testing. Rock or wet soil adds cost. |
Common questions
Can I run power to a detached garage without a permit if I hire a licensed electrician?
No. A permit is required regardless of who does the work. The code—NEC Article 225 and your local building code—requires a permit for any new feeder or branch circuit to a detached structure. A licensed electrician will not do the job without a permit because they lose their license if caught working unpermitted. The electrician will file the permit (or help you file it, depending on your state). The permit is non-negotiable.
How long does it take to get an electrical permit for a detached structure?
Simple branch circuits (20–30 amps, under 75 feet) typically approve over-the-counter or within 1–2 business days. Feeders and subpanels usually go to plan review and take 2–4 weeks. Service upgrades with multiple components can take 4–6 weeks or longer if third-party review is required. Once the permit is issued, inspections are usually scheduled within 1–2 weeks. Total timeline from filing to final sign-off: 2–3 weeks for simple jobs, 6–10 weeks for complex ones. Call your building department to ask for their average review time and inspection availability.
What's the difference between running power as a branch circuit vs. a feeder, and why does it matter for the permit?
A branch circuit is a single circuit protected by one breaker, typically 15 or 20 amps at 120 volts, serving a small area (a few outlets, a light). A feeder is a larger conductor serving an entire building or subpanel, typically 60–200 amps at 240 volts. Branch circuits under 75 feet usually qualify for expedited permits and may not require plan review. Feeders, especially over 100 feet, require full plan review, load calculations, and multiple inspections. The permit fee and timeline reflect this: branch circuits cost $50–$150 and take 1–2 weeks; feeders cost $200–$500 and take 3–4 weeks. If your detached structure is far from the main panel or has a large load (a subpanel, workshop equipment, etc.), you'll likely need a feeder and a longer permit timeline.
Do I need a separate permit for the subpanel in the detached structure, or does the feeder permit cover it?
In most jurisdictions, a single electrical permit covers both the feeder and the subpanel as one project. You'll file one permit application with details on both. However, some jurisdictions (notably Florida and a few California counties) issue separate subpanel permits. Call your building department to ask: 'If I'm running a feeder to a detached garage subpanel, do I file one permit or two?' They'll clarify their process. Regardless, you'll have inspection points for both the feeder (roughin before backfill) and the subpanel (roughin after installation, final after wiring).
If the detached structure is far away (150+ feet), do I need an engineer to design the installation?
Not always, but often. At very long distances, voltage drop becomes the limiting factor. NEC Article 210.19 limits voltage drop to 3% on branch circuits and 5% combined (feeder + branch). A 20-amp branch circuit 150 feet away would require 6 AWG wire or larger—or a subpanel closer to the load. Most jurisdictions expect a licensed electrician to size the wire correctly; some require an engineer-stamped design if the run exceeds 200 feet or involves unusual conditions (very large load, multiple subpanels, etc.). When in doubt, ask the electrician to design the job and have the plans ready to submit with the permit. If an engineer review is required, the building department will ask for it during plan review—you can't add it mid-way. Plan ahead.
What happens if I run power to a detached structure without a permit?
You're in violation of your local building code. If the work is discovered during a future sale, inspection, or when a neighbor complains, the city will issue a citation and require you to obtain a permit retroactively—which means an inspector will reinspect the work and may require you to fix code violations at your expense. You could also face fines (typically $100–$1,000 depending on jurisdiction) and difficulty selling the property (the title company or lender may require a permit and inspection before closing). More importantly, unpermitted electrical work is a fire and safety hazard. A licensed electrician who discovers unpermitted work in a home they're hired to modify is required to report it in many states. The safe and legal move is a 10-minute phone call to your building department to confirm what you need, then follow the process. It costs $75–$300 and takes 2–4 weeks. It's worth it.
Can a homeowner do the electrical work themselves, or does a licensed electrician have to do it?
This varies by state. Most states allow homeowners to perform electrical work on their own primary residence without a license, provided the work meets code and is permitted and inspected. California, New York, Illinois, and Florida require a licensed electrician for nearly all electrical work. Some states (Arizona, Colorado) allow homeowner-performed work but still require a licensed electrician to pull the permit. Check your state's electrical licensing board website (search '[State] electrical licensing board' or '[State] contractor's license board'). Call them or visit their site to confirm. If you're allowed to do it yourself, you'll still need a permit, and the work will still be inspected. Many homeowners save money on permit fees by doing simple branch circuits themselves; others hire a licensed electrician for safety and warranty reasons.
How deep does the underground conduit need to be buried?
Burial depth depends on your local frost depth and soil type. In Minnesota, Wisconsin, and Vermont, conduit must be buried below the frost line—typically 48–60 inches below grade. In Georgia, South Carolina, or southern California, 18–24 inches is often sufficient. Your local building department or county soil survey will specify the frost depth. If you can't meet the minimum depth due to bedrock or water table, propose an alternative with the building department: concrete encasement (burying the conduit in concrete) or above-ground protection. The building department may approve the alternative, or the inspector may require it during the footing inspection. Never bury conduit shallower than code without prior approval—the inspector will mark it as a violation.
What permits do I need if I'm building a detached ADU (accessory dwelling unit) and running power to it?
You'll need multiple permits: a building permit (for the ADU structure itself), an electrical permit (for the feeder and subpanel), and often a plumbing permit (if the ADU has a kitchen or bathroom). Some jurisdictions require the building permit to be approved first, then the electrical permit issued after. Others allow concurrent filing. Call your building department to ask the sequence. The electrical portion will follow the same process as any detached structure: feeder design, site plan, subpanel, and multiple inspections. Total timeline: 4–10 weeks depending on complexity and review speed.
Ready to move forward?
Start by calling your local building department and confirming three things: whether your project needs a permit (it almost certainly does), who can pull the permit (homeowner or licensed electrician), and what documents to submit. Most building departments can answer all three questions in a 10-minute call. Have your property address, a rough sketch of the distance from your main panel to the detached structure, and an idea of the scope (how many outlets, what voltage, overhead or underground) ready. Once you have clarity, you can either file the permit yourself (if allowed) or ask a licensed electrician to file as part of their bid. Either way, permitting a detached structure is straightforward—the front-end conversation with the building department is the most important step.
Related permit guides
Other guides in the Electrical category: