Aiken's rural character means many properties include barns, workshops, detached garages, storage buildings, and other outbuildings that need electrical service. Whether you are building a new barn for horses, converting a shed into a woodworking shop, or running power to a well pump house, the electrical requirements for outbuildings differ significantly from standard residential work. Getting the underground feeder, subpanel, and wiring right from the start saves money and keeps your building safe.
Getting Power to the Outbuilding: Underground Feeder
The first major decision is how to get electricity from your home's main panel to the outbuilding. For most Aiken properties, underground feeder cable is the standard approach. Overhead runs are possible but less common for residential properties due to clearance requirements, aesthetics, and vulnerability to storm damage.
Underground wiring methods and trench depths:
- Direct-burial UF-B cable: Must be buried at least 24 inches deep. This is the simplest method for short runs but is limited to smaller amperage feeds and cannot be easily replaced if damaged
- PVC conduit (Schedule 40): Must be buried at least 18 inches deep. This is the most common method for outbuilding feeds because the conduit protects the wire and allows replacement or upgrades by pulling new wire through the existing conduit
- Rigid metal conduit (RMC): Can be buried at only 6 inches deep, but the material cost is much higher. Rarely used for long residential runs
- PVC conduit under a driveway or parking area: Must be at least 18 inches deep and should use Schedule 80 PVC for the section under the driving surface to handle the additional weight
For most Aiken outbuilding projects, we recommend PVC conduit at 24 inches deep. The extra depth beyond the 18-inch minimum provides additional protection against accidental damage from gardening, grading, or future landscaping work. We also install a continuous run of underground warning tape 12 inches above the conduit to alert anyone digging in the area.
The wire inside the conduit is typically THWN-2 rated copper or aluminum conductors. For runs over 100 feet, aluminum feeder wire is common because it costs significantly less than copper at larger sizes, and the slight increase in wire gauge required for aluminum is a worthwhile trade-off at these distances.
Subpanel Sizing: Plan for What You Need and What You Might Need
Every outbuilding with more than a couple of circuits should have its own subpanel. The subpanel serves as the local distribution point and disconnect for the building. NEC requires a disconnect at or near the building entrance, and a subpanel with a main breaker satisfies this requirement.
Common subpanel sizes for Aiken outbuildings:
- 60 amps: Suitable for a basic workshop or barn with lighting, a few outlets, and small power tools. Handles most 120V loads comfortably
- 100 amps: The standard choice for a serious workshop, large barn, or outbuilding with 240V equipment like welders, air compressors, or well pumps. Provides room for growth
- 200 amps: Required for buildings with heavy loads like commercial equipment, large horse barns with heated wash stalls and multiple water heaters, or buildings that essentially function as a second residence
Our advice is always to size the subpanel one step larger than your current needs. The cost difference between a 60-amp and 100-amp subpanel is modest, but upgrading later means replacing the panel, the feeder wire, and the breaker in the main panel. A 100-amp subpanel with 20 to 24 circuit spaces is the sweet spot for most Aiken outbuilding projects.
Grounding Requirements for Detached Buildings
Outbuilding electrical systems have specific grounding requirements that differ from the main house. The NEC requires a separate grounding electrode system at each detached building served by a feeder circuit. This typically means driving one or two ground rods at the outbuilding and connecting them to the subpanel's grounding bus.
In the subpanel, the neutral bus and ground bus must be separated, unlike the main panel where they are bonded together. This is a critical detail that is frequently done incorrectly in DIY installations. Bonding neutral and ground in a subpanel creates parallel paths for current that can energize metal building components and create shock hazards.
For metal buildings, which are common for barns and workshops in the Aiken area, the building frame itself should be bonded to the grounding electrode system. This ensures that any fault current on the metal skin of the building has a safe path to ground rather than through a person who touches the building.
Wiring Inside the Outbuilding
The wiring method inside the outbuilding depends on the building type and use:
- Finished buildings (drywall or paneling): Standard NM-B cable (Romex) is acceptable, just like in a house. Run through stud bays before finishing the walls
- Unfinished buildings (exposed framing): NM-B cable can be used but must be protected from physical damage. In areas subject to damage, run cable through conduit or use armored cable (MC). Cables running across exposed joists must be protected by running boards
- Metal buildings: Use conduit (EMT or PVC) or MC cable throughout. NM-B cable should not contact metal building components that could chafe through the jacket over time
- Barns with livestock: NEC Article 547 applies to agricultural buildings. Wiring must be in conduit, MC cable, or other raceway systems. Standard NM-B cable is not permitted in areas housing livestock due to moisture, corrosion, and physical damage risks
Lighting for outbuildings: LED fixtures are the clear choice for barns and workshops. They provide excellent light output, resist vibration better than fluorescent tubes, work well in cold temperatures, and use a fraction of the energy. For barns, look for fixtures rated for damp or wet locations and consider dust-tight rated fixtures in hay storage areas. For workshops, high-bay LED fixtures at 5000K color temperature provide bright, natural-looking light ideal for detailed work.
Well Pump Circuits
Many Aiken properties outside city water service rely on well pumps, which are frequently located in or near outbuildings. Well pump electrical requirements include:
- Dedicated circuit: Well pumps must be on their own dedicated circuit with no other loads. The circuit size depends on the pump motor, typically 20 amps for smaller pumps up to 1 HP and 30 amps for larger pumps
- Disconnect switch: A disconnect must be located within sight of the pump or pressure tank. This allows the pump to be safely serviced without walking back to the panel
- Lightning protection: Well pump circuits are particularly vulnerable to lightning damage because the underground water pipe and well casing act as a ground path. A surge protector on the pump circuit is a worthwhile investment in Aiken's thunderstorm-prone climate
- Control wiring: Submersible well pumps require control wiring between the pump, the pressure switch, and the panel. This wiring must be appropriately rated for direct burial if it runs underground between the well head and the building
Permits and Agricultural Considerations
Electrical permits are required for outbuilding wiring in Aiken County, including agricultural buildings. The permitting process is the same as for residential electrical work: a licensed contractor pulls the permit, the work is inspected at the rough-in and final stages, and the project is closed out when it passes.
South Carolina does not provide blanket exemptions for agricultural electrical work. While some states allow farm owners to perform their own electrical work on agricultural buildings, South Carolina requires licensed contractors for permitted electrical work. The NEC's agricultural building requirements in Article 547 actually add complexity compared to standard residential work, making professional installation particularly important.
Common permit triggers for outbuilding electrical work include new service or feeder installations, subpanel installations, any new circuits, well pump connections, and modifications to existing wiring. The one area that typically does not require a permit is replacing fixtures or devices on existing circuits in kind, such as swapping a light fixture or replacing an outlet.
Cost Expectations for Aiken Outbuilding Wiring
Outbuilding electrical costs vary widely based on distance from the main panel, building size, and intended use. Here are typical ranges for Aiken-area projects:
- Underground feeder (trench, conduit, wire): $15 to $25 per linear foot for a 100-amp feed. A 150-foot run from house to barn costs roughly $2,500 to $4,000 for the feeder alone
- Subpanel installation: $1,200 to $2,500 including the panel, breakers, grounding electrode, and connections
- Interior wiring (basic barn or workshop): $3,000 to $8,000 depending on circuit count, outlet quantity, and lighting
- Total project (typical workshop or barn): $6,000 to $15,000 depending on all factors
Trenching is often the biggest variable. If the trench can be dug with a trencher or mini excavator across open ground, costs are lower. If the run crosses driveways, decks, landscaping, or rocky soil, expect higher trenching costs. Some homeowners save money by digging the trench themselves to the electrician's specifications, and we are happy to work with that arrangement.
Get Your Outbuilding Wired Right
Whether you are wiring a horse barn, a woodworking shop, a detached garage, or a storage building, the electrical system needs to be planned and installed correctly from the start. Outbuilding electrical work involves underground installation, separate grounding systems, and specific code requirements that differ from house wiring. Unity Power & Light has extensive experience wiring barns and outbuildings throughout the Aiken area. Contact us for a free on-site evaluation and quote for your project.